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C and C++ XML Data Bindings

updated Wed Mar 1 2017 by Robert van Engelen
 
C and C++ XML Data Bindings

Table of Contents

Introduction

This article gives a detailed overview of the gSOAP C and C++ XML data bindings and highlights the advantages, concepts, usage, and implementation aspects of XML data bindings.

The major advantage of XML data bindings is that your application data is always type safe in C and C++ by binding XML schema types to C/C++ types. So integers in XML are bound to C integers, strings in XML are bound to C or C++ strings, complex types in XML are bound to C structs or C++ classes, and so on. The structured data you create and accept will fit the data model and is static type safe. In other words, by leveraging strong typing in C/C++, your XML data meets XML validation requirements and satisfies XML interoperability requirements.

The gSOAP data bindings are more powerful than simply representing C/C++ data in XML. In fact, the tools implement true serialization of C/C++ data in XML, including the serialization of cyclic graph structures. The gSOAP tools also generate routines for deep copying and deep deletion of C/C++ data structures to simplify memory management. In addition, C/C++ structures are deserialized into managed memory, managed by the gSOAP soap context.

At the end of this document two examples are given to illustrate the application of XML data bindings. The first simple example address.cpp shows how to use wsdl2h to bind an XML schema to C++. The C++ application reads and writes an XML file into and from a C++ "address book" data structure. The C++ data structure is an STL vector of address objects. The second example graph.cpp shows how C++ data can be accurately serialized as a tree, digraph, and cyclic graph in XML. The digraph and cyclic graph serialization rules implement SOAP 1.1/1.2 multi-ref encoding with id-ref attributes to link elements through IDREF XML references, creating a an XML graph with pointers to XML nodes that preserves the structural integrity of the serialized C++ data.

These examples demonstrate XML data bindings only for relatively simple data structures and types. The gSOAP tools support more than just these type of structures to serialize in XML. There are practically no limits to enable XML serialization of C and C++ types.

Support for XML schema components is unlimited. The wsdl2h tool maps schemas to C and C++ using built-in intuitive mapping rules, while allowing the mappings to be customized using a typemap.dat file with mapping instructions for wsdl2h.

The information in this document is applicable to gSOAP 2.8.26 and later versions that support C++11 features. However, C++11 is not required to use this material and the examples included, unless we need smart pointers and scoped enumerations. While most of the examples in this document are given in C++, the concepts also apply to C with the exception of containers, smart pointers, classes and their methods. None of these exceptions limit the use of the gSOAP tools for C in any way.

The data binding concepts described in this document were first envisioned in 1999 by Prof. Robert van Engelen at the Florida State University. An implementation was created in 2000, named "stub/skeleton compiler". The first articles on its successor version "gSOAP" appeared in 2002. The principle of mapping XSD components to C/C++ types and vice versa is now widely adopted in systems and programming languages, including Java web services and by C# WCF.

We continue to be committed to our goal to empower C/C++ developers with powerful autocoding tools for XML. Our commitment started in the very early days of SOAP by actively participating in SOAP interoperability testing, participating in the development and testing of the W3C XML Schema Patterns for Databinding Interoperability, and continues by contributing to the development of OASIS open standards in partnership with leading IT companies.

Mapping WSDL and XML schemas to C/C++

To convert WSDL and XML schemas (XSD files) to code, use the wsdl2h command to generate the data binding interface code that is saved to a special gSOAP header file with WSDL service declarations and the data binding interface:

wsdl2h [options] -o file.h ... XSD and WSDL files ...

This command converts WSDL and XSD files to C++ (or pure C with wsdl2h option -c) and saves the data binding interface to a gSOAP header file file.h that uses familiar C/C++ syntax extended with //gsoap directives and annotations. Notational conventions are used in the data binding interface to declare serializable C/C++ types and functions for Web service operations.

The WSDL 1.1/2.0, SOAP 1.1/1.2, and XSD 1.0/1.1 standards are supported by the gSOAP tools. In addition, the most popular WS specifications are also supported, including WS-Addressing, WS-ReliableMessaging, WS-Discovery, WS-Security, WS-Policy, WS-SecurityPolicy, and WS-SecureConversation.

This document focusses on XML data bindings. XML data bindings for C/C++ bind XML schema types to C/C++ types. So integers in XML are bound to C integers, strings in XML are bound to C or C++ strings, complex types in XML are bound to C structs or C++ classes, and so on.

A data binding is dual. Either you start with WSDLs and/or XML schemas that are mapped to equivalent C/C++ types, or you start with C/C++ types that are mapped to XSD types. Either way, the end result is that you can serialize C/C++ types in XML such that your XML is an instance of XML schema(s) and is validated against these schema(s).

This covers all of the following standard XSD components with their optional attributes and properties:

XSD Component Attributes and Properties
schema targetNamespace, version, elementFormDefault, attributeFormDefault, defaultAttributes
attribute name, ref, type, use, default, fixed, form, targetNamespace, wsdl:arrayType
element name, ref, type, default, fixed, form, nillable, abstract, substitutionGroup, minOccurs, maxOccurs, targetNamespace
simpleType name
complexType name, abstract, mixed, defaultAttributesApply
all
choice minOccurs, maxOccurs
sequence minOccurs, maxOccurs
group name, ref, minOccurs, maxOccurs
attributeGroup name, ref
any minOccurs, maxOccurs
anyAttribute

And also the following standard XSD directives are covered:

Directive Description
import Imports a schema into the importing schema for referencing
include Include schema component definitions into a schema
override Override by replacing schema component definitions
redefine Extend or restrict schema component definitions
annotation Annotates a component

The XSD facets and their mappings to C/C++ are:

XSD Facet Maps to
enumeration enum
simpleContent class/struct wrapper with __item member
complexContent class/struct
list enum* bitmask (enum* enumerates up to 64 bit masks)
extension class/struct inheritance/extension
restriction typedef and class/struct inheritance/redeclaration
length typedef with restricted content length annotation
minLength typedef with restricted content length annotation
maxLength typedef with restricted content length annotation
minInclusive typedef with numerical value range restriction annotation
maxInclusive typedef with numerical value range restriction annotation
minExclusive typedef with numerical value range restriction annotation
maxExclusive typedef with numerical value range restriction annotation
precision typedef with pattern annotation (pattern used for output, but input is not validated)
scale typedef with pattern annotation (pattern used for output, but input is not validated)
totalDigits typedef with pattern annotation (pattern used for output, but input is not validated)
fractionDigits typedef with pattern annotation (pattern used for output, but input is not validated)
pattern typedef with pattern annotation (define soap::fsvalidate callback to validate patterns)
union string with union of values

All primitive XSD types are supported, including but not limited to the following XSD types:

XSD Type Maps to
any/anyType _XML string with literal XML content (or enable DOM with wsdl2h option -d)
anyURI string (i.e. char*, wchar_t*, std::string, std::wstring)
string string (i.e. char*, wchar_t*, std::string, std::wstring)
boolean bool (C++) or enum xsd__boolean (C)
byte char (i.e. int8_t)
short short (i.e. int16_t)
int int (i.e. int32_t)
long LONG64 (i.e. long long and int64_t)
unsignedByte unsigned char (i.e. uint8_t)
unsignedShort unsigned short (i.e. uint16_t)
unsignedInt unsigned int (i.e. uint32_t)
unsignedLong ULONG64 (i.e. unsigned long long and uint64_t)
float float
double double
integer string or #import "custom/int128.h" to use 128 bit xsd__integer
decimal string or #import "custom/long_double.h" to use long double
precisionDecimal string
duration string or #import "custom/duration.h" to use 64 bit xsd__duration
dateTime time_t or #import "custom/struct_tm.h" to use struct tm for xsd__dateTime
time string or #import "custom/long_time.h" to use 64 bit xsd__time
date string or #import "custom/struct_tm_date.h" to use struct tm for xsd__date
hexBinary special class/struct xsd__hexBinary
base64Bianry special class/struct xsd__base64Binary
QName _QName string (URI normalization rules are applied)

All other primitive XSD types not listed above are mapped to strings, by wsdl2h generating a typedef to string for these types. For example, xsd:token is bound to a C++ or C string:

typedef std::string xsd__token; // C++
typedef char *xsd__token; // C (wsdl2h option -c)

This associates a compatible value space to the type with the appropriate XSD type name used by the soapcpp2-generated serializers.

It is possible to remap types by adding the appropriate mapping rules to typemap.dat as we will explain in more detail in the next section.

Imported custom serializers are intended to extend the C/C++ type bindings when the default binding to string is not satisfactory to your taste and if the target platform supports these C/C++ types. To add custom serializers to typemap.dat for wsdl2h, see adding custom serializers below.

Using typemap.dat to customize data bindings

Use a typemap.dat file to redefine namespace prefixes and to customize type bindings for the the generated header files produced by the wsdl2h tool. The typemap.dat is the default file processed by wsdl2h. Use wsdl2h option -t to specify a different file.

Declarations in typemap.dat can be broken up over multiple lines by continuing on the next line by ending each line to be continued with a backslash \. The limit is 4095 characters per line, whether the line is broken up or not.

XML namespace bindings

The wsdl2h tool generates C/C++ type declarations that use ns1, ns2, etc. as schema-binding URI prefixes. These default prefixes are generated somewhat arbitrarily for each schema targetNamespace URI, meaning that their ordering may change depending on the WSDL and XSD order of processing with wsdl2h.

Therefore, it is strongly recommended to declare your own prefix for each schema URI in typemap.dat to reduce maintaince effort of your code. This is more robust when anticipating possible changes of the schema(s) and/or the binding URI(s) and/or the tooling algorithms.

The first and foremost important thing to do is to define prefix-URI bindings for our C/C++ code by adding the following line(s) to our typemap.dat or make a copy of this file and add the line(s) that bind our choice of prefix name to each URI:

prefix = "URI"

For example, to use g as a prefix for the "urn:graph" XML namespace:

g = "urn:graph"

This produces g__name C/C++ type names that are bound to the "urn:graph" schema by association of g to the generated C/C++ types.

This means that <g:name xmlns:g="urn:graph"> is parsed as an instance of a g__name C/C++ type. Also <x:name xmlns:x="urn:graph"> parses as an instance of g__name, because the prefix x has the same URI value urn:graph. Prefixes in XML have local scopes (like variables in a block).

The first run of wsdl2h will reveal the XML namespace URIs, so you do not need to search WSDLs and XSD files for all of the target namespaces. Just copy them from the generated header file after the first run into typemap.dat for editing.

Note
Only define a namespace prefix once in typemap.dat. That is, do not use the same prefix for multiple XML namespace URIs. This is to avoid namespace conflicts that may cause failed builds and failures in XML parsing and validation.

XSD type bindings

Custom C/C++ type bindings can be declared in typemap.dat to associate C/C++ types with specific schema types. These type bindings have four parts:

prefix__type = declaration | use | ptruse

where

  • prefix__type is the schema type to be customized (the prefix__type name uses the common double underscore naming convention);
  • declaration declares the C/C++ type in the wsdl2h-generated header file. This part can be empty if no explicit declaration is needed;
  • use is an optional part that specifies how the C/C++ type is used in the code. When omitted, it is the same as prefix__type;
  • ptruse is an optional part that specifies how the type is used as a pointer type. By default it is the use type name with a * or C++11 std::shared_ptr<> when enabled (see further below). If use is already a pointer type by the presence of a * in the use part, then the default ptruse type is the same as the use type (that is, no double pointer ** will be created in this case).

For example, to map xsd:duration to a long long (LONG64) type that holds millisecond duration values, we can use the custom serializer declared in custom/duration.h by adding the following line to typemap.dat:

xsd__duration = #import "custom/duration.h"

Here, we omitted the second and third parts, because xsd__duration is the name that wsdl2h uses for this type in our generated code so we should leave the use part unspecified. The third part is omitted to let wsdl2h use xsd__duration * for pointers or std::shared_ptr<xsd__duration> if smart pointers are enabled.

To map xsd:string to wchar_t* wide strings:

xsd__string = | wchar_t* | wchar_t*

Note that the first part is empty, because wchar_t is a C type and does not need to be declared. A ptruse part is also defined in this example, but does not need to be because the use part wchar_t* is already a pointer.

When the auto-generated declaration should be preserved but the use or ptruse parts replaced, then we use an ellipsis for the declaration part:

prefix__type = ... | use | ptruse

This is useful to map schema polymorphic types to C types for example, where we need to be able to both handle a base type and its extensions as per schema extensibility. Say we have a base type called ns:base that is extended, then we can remap this to a C type that permits referening the extended types via a void* as follows:

ns__base = ... | int __type_base; void*

such that __type_base and void* will be used to (de)serialize any data type, including base and its derived types. The __type_base integer is set to a SOAP_TYPE_T value to indicate what type of data the void* pointer points to.

Custom serializers for XSD types

In the previous part we saw how a custom serializer is used to bind xsd:duration to a long long (LONG64 or int64_t) type to store millisecond duration values:

xsd__duration = #import "custom/duration.h"

The xsd__duration type is an alias of long long (LONG64 or int64_t).

While wsdl2h will use this binding declared in typemap.dat automatically, you will also need to compile custom/duration.c. Each custom serializer has a header file and an implementation file written in C. You can compile these in C++ (rename files to .cpp if needed).

We will discuss the custom serializers that are available to you.

xsd:integer

The wsdl2h tool maps xsd:integer to a string by default. To map xsd:integer to the 128 bit big int type __int128_t:

xsd__integer = #import "custom/int128.h"

The xsd__integer type is an alias of __int128_t.

Warning
Beware that the xsd:integer value space of integers is in principle unbounded and values can be of arbitrary length. A value range fault SOAP_TYPE (value exceeds native representation) or SOAP_LENGTH (value exceeds range bounds) will be thrown by the deserializer if the value is out of range.

Other XSD integer types that are restrictions of xsd:integer, are xsd:nonNegativeInteger and xsd:nonPositiveInteger, which are further restricted by xsd:positiveInteger and xsd:negativeInteger. To bind these types to __int128_t add the following definitions to typemap.dat:

xsd__nonNegativeInteger = typedef xsd__integer xsd__nonNegativeInteger 0 :    ;
xsd__nonPositiveInteger = typedef xsd__integer xsd__nonPositiveInteger   : 0  ;
xsd__positiveInteger    = typedef xsd__integer xsd__positiveInteger    1 :    ;
xsd__negativeInteger    = typedef xsd__integer xsd__negativeInteger      : -1 ;

Or simply uncomment these definitions in typemap.dat when you are using the latest gSOAP releases.

Note
If __int128_t 128 bit integers are not supported on your platform and if it is certain that xsd:integer values are within 64 bit value bounds for your application's use, then you can map this type to LONG64:
xsd__integer = typedef LONG64 xsd__integer;
Again, a value range fault SOAP_TYPE or SOAP_LENGTH will be thrown by the deserializer if the value is out of range.

After running wsdl2h and soapcpp2, compile custom/int128.c with your project.

See also
Section numerical types.

xsd:decimal

The wsdl2h tool maps xsd:decimal to a string by default. To map xsd:decimal to extended precision floating point:

xsd__decimal = #import "custom/long_double.h" | long double

By contrast to all other custom serializers, this serializer enables long double natively without requiring a new binding name (xsd__decimal is NOT defined).

If your system supports <quadmath.h> quadruple precision floating point __float128, you can map xsd:decimal to xsd__decimal that is an alias of __float128:

xsd__decimal = #import "custom/float128.h"
Warning
Beware that xsd:decimal is in principle a decimal value with arbitraty lengths. A value range fault SOAP_TYPE will be thrown by the deserializer if the value is out of range.

In the XML payload the special values INF, -INF, NaN represent plus or minus infinity and not-a-number, respectively.

After running wsdl2h and soapcpp2, compile custom/long_double.c with your project.

See also
Section numerical types.

xsd:dateTime

The wsdl2h tool maps xsd:dateTime to time_t by default.

The trouble with time_t when represented as 32 bit long integers is that it is limited to dates between 1970 and 2038. A 64 bit time_t is safe to use if the target platform supports it, but lack of 64 bit time_t portability may still cause date range issues.

For this reason struct tm should be used to represent wider date ranges. This custom serializer avoids using date and time information in time_t. You get the raw date and time information. You only lose the day of the week information. It is always Sunday (tm_wday=0).

To map xsd:dateTime to xsd__dateTime which is an alias of struct tm:

xsd__dateTime = #import "custom/struct_tm.h"

If the limited date range of time_t is not a problem but you want to increase the time precision with fractional seconds, then we suggest to map xsd:dateTime to struct timeval:

xsd__dateTime = #import "custom/struct_timeval.h"

If the limited date range of time_t is not a problem but you want to use the C++11 time point type std::chrono::system_clock::time_point (which internally uses time_t):

xsd__dateTime = #import "custom/chrono_time_point.h"

Again, we should make sure that the dates will not exceed the date range when using the default time_t binding for xsd:dateTime or when binding xsd:dateTime to struct timeval or to std::chrono::system_clock::time_point. These are safe to use in applications that use xsd:dateTime to record date stamps within a given window. Otherwise, we recommend the struct tm custom serializer.

After running wsdl2h and soapcpp2, compile custom/struct_tm.c with your project.

You could even map xsd:dateTime to a plain string (use char* with C and std::string with C++). For example:

xsd__dateTime = | char*
See also
Section date and time types.

xsd:date

The wsdl2h tool maps xsd:date to a string by default. We can map xsd:date to struct tm:

xsd__date = #import "custom/struct_tm_date.h"

The xsd__date type is an alias of struct tm. The serializer ignores the time part and the deserializer only populates the date part of the struct, setting the time to 00:00:00. There is no unreasonable limit on the date range because the year field is stored as an integer (int).

After running wsdl2h and soapcpp2, compile custom/struct_tm_date.c with your project.

See also
Section date and time types.

xsd:time

The wsdl2h tool maps xsd:time to a string by default. We can map xsd:time to an unsigned long long (ULONG64 or uint64_t) integer with microsecond time precision:

xsd__time = #import "custom/long_time.h"

This type represents 00:00:00.000000 to 23:59:59.999999, from 0 to an upper bound of 86399999999. A microsecond resolution means that a 1 second increment requires an increment of 1000000 in the integer value. The serializer adds a UTC time zone.

After running wsdl2h and soapcpp2, compile custom/long_time.c with your project.

See also
Section date and time types.

xsd:duration

The wsdl2h tool maps xsd:duration to a string by default, unless xsd:duration is mapped to a long long (LONG64 or int64_t) type with with millisecond (ms) time duration precision:

xsd__duration = #import "custom/duration.h"

The xsd__duration type is a 64 bit signed integer that can represent 106,751,991,167 days forwards (positive) and backwards (negative) in time in increments of 1 ms (1/1000 of a second).

Rescaling of the duration value by may be needed when adding the duration value to a time_t value, because time_t may or may not have a seconds resolution, depending on the platform and possible changes to time_t.

Rescaling is done automatically when you add a C++11 std::chrono::nanoseconds value to a std::chrono::system_clock::time_point value. To use std::chrono::nanoseconds as xsd:duration:

xsd__duration = #import "custom/chrono_duration.h"

This type can represent 384,307,168 days (2^63 nanoseconds) forwards and backwards in time in increments of 1 ns (1/1,000,000,000 of a second).

Certain observations with respect to receiving durations in years and months apply to both of these serializer decoders for xsd:duration.

After running wsdl2h and soapcpp2, compile custom/duration.c with your project.

See also
Section time duration types.

Custom Qt serializers for XSD types

The gSOAP distribution includes several custom serializers for Qt types. Also Qt container classes are supported, see the built-in typemap.dat variables $CONTAINER and $POINTER.

This feature requires gSOAP 2.8.34 or higher and Qt 4.8 or higher.

Each Qt custom serializer has an interface header file for soapcpp2 and a C++ implementation file to be compiled with your project.

Other Qt primitive types that are Qt typedefs of C/C++ types do not require a custom serializer.

xsd:string

To use Qt strings instead of C++ strings, add the following definition to typemap.dat:

xsd__string = #import "custom/qstring.h"

After running wsdl2h and soapcpp2, compile custom/qstring.cpp with your project.

xsd:base64Binary

To use Qt byte arrays for xsd:base64Binary instead of the xsd__base64Binary class, add the following definition to typemap.dat:

xsd__base64Binary = #import "custom/qbytearray_base64.h"

After running wsdl2h and soapcpp2, compile custom/qbytearray_base64.cpp with your project.

xsd:hexBinary

To use Qt byte arrays for xsd:hexBinary instead of the xsd__base64Binary class, add the following definition to typemap.dat:

xsd__hexBinary = #import "custom/qbytearray_hex.h"

After running wsdl2h and soapcpp2, compile custom/qbytearray_hex.cpp with your project.

xsd:dateTime

To use Qt QDateTime for xsd:dateTime, add the following definition to typemap.dat:

xsd__dateTime = #import "custom/datetime.h"

After running wsdl2h and soapcpp2, compile custom/qdatetime.cpp with your project.

xsd:date

To use Qt QDate for xsd:date, add the following definition to typemap.dat:

xsd__date = #import "custom/qdate.h"

After running wsdl2h and soapcpp2, compile custom/qdate.cpp with your project.

xsd:time

To use Qt QDate for xsd:time, add the following definition to typemap.dat:

xsd__time = #import "custom/qtime.h"

After running wsdl2h and soapcpp2, compile custom/qtime.cpp with your project.

Class/struct member additions

All generated classes and structs can be augmented with additional members such as methods, constructors and destructors, and private members:

prefix__type = $ member-declaration

For example, we can add method declarations and private members to a class, say ns__record as follows:

ns__record = $ ns__record(const ns__record &); // copy constructor
ns__record = $ void print();                   // a print method
ns__record = $ private: int status;            // a private member

Note that method declarations cannot include any code, because soapcpp2's input permits only type declarations, not code.

Replacing XSD types by equivalent alternatives

Type replacements can be given to replace one type entirely with another given type:

prefix__type1 == prefix__type2

This replaces all prefix__type1 by prefix__type2 in the wsdl2h output.

Warning
Do not agressively replace types, because this can cause XML validation to fail when a value-type mismatch is encountered in the XML input. Therefore, only replace similar types with other similar types that are wider (e.g. short by int and float by double).

The built-in typemap.dat variables $CONTAINER and $POINTER

The typemap.dat $CONTAINER variable defines the container to emit in the generated declarations, which is std::vector by default. For example, to emit std::list as the container in the wsdl2h-generated declarations:

$CONTAINER = std::list

The typemap.dat $POINTER variable defines the smart pointer to emit in the generated declarations, which replaces the use of * pointers. For example:

$POINTER = std::shared_ptr

Not all pointers in the generated output can be replaced by smart pointers. Regular pointers are still used as union members and for pointers to arrays of objects.

Note
The standard smart pointer std::shared_ptr is generally safe to use. Other smart pointers such as std::unique_ptr and std::auto_ptr may cause compile-time errors when classes have smart pointer members but no copy constructor (a default copy constructor). A copy constructor is required for non-shared smart pointer copying or swapping.

Alternatives to std::shared_ptr of the form NAMESPACE::shared_ptr can be assigned to $POINTER when the namespace NAMESPACE also implements NAMESPACE::make_shared and when the shared pointer class provides reset() andget() methods and the dereference operator. For example Boost boost::shared_ptr:

[
#include <boost/shared_ptr.hpp>
]
$POINTER = boost::shared_ptr

The user-defined content between [ and ] ensures that we include the Boost header files that are needed to support boost::shared_ptr and boost::make_shared.

A Qt container can be used instead of the default std::vector, for example QVector:

[
#include <QVector>
]
$CONTAINER = QVector

User-defined content

Any other content to be generated by wsdl2h can be included in typemap.dat by enclosing it within brackets [ and ] anywhere in the typemap.dat file. Each of the two brackets MUST appear at the start of a new line.

For example, we can add an #import "wsa5.h" to the wsdl2h-generated output as follows:

[
#import "import/wsa5.h"
]

which emits the #import "import/wsa5.h" literally at the start of the wsdl2h-generated header file.

Mapping C/C++ to XML schema

The soapcpp2 command generates the data binding implementation code from a data binding interface file.h:

soapcpp2 [options] file.h

where file.h is a gSOAP header file that declares the XML data binding interface. The file.h is typically generated by wsdl2h, but you can also declare one yourself. If so, add //gsaop directives and declare in this file all our C/C++ types you want to serialize in XML.

You can also declare functions that will be converted to Web service operations by soapcpp2. Global function declarations define service operations, which are of the form:

int prefix__func(arg1, arg2, ..., argn, result);

where arg1, arg2, ..., argn are formal argument declarations of the input and result is a formal argument for the output, which must be a pointer or reference to the result object to be populated. More information can be found in the gSOAP user guide.

Overview of serializable C/C++ types

The following C/C++ types are supported by soapcpp2 and mapped to XSD types and constructs. See the subsections below for more details or follow the links.

List of Boolean types

Boolean Type Notes
bool C++ bool
enum xsd__boolean C alternative to C++ bool with false_ and true_
See also
Section C++ bool and C alternative.

List of enumeration and bitmask types

Enumeration Type Notes
enum enumeration
enum class C++11 scoped enumeration (soapcpp2 -c++11)
enum* a bitmask that enumerates values 1, 2, 4, 8, ...
enum* class C++11 scoped enumeration bitmask (soapcpp2 -c++11)
See also
Section enumerations and bitmasks.

List of numerical types

Numerical Type Notes
char byte
short 16 bit integer
int 32 bit integer
long 32 bit integer
LONG64 64 bit integer
xsd__integer 128 bit integer, use #import "custom/int128.h"
long long same as LONG64
unsigned char unsigned byte
unsigned short unsigned 16 bit integer
unsigned int unsigned 32 bit integer
unsigned long unsigned 32 bit integer
ULONG64 unsigned 64 bit integer
unsigned long long same as ULONG64
int8_t same as char
int16_t same as short
int32_t same as int
int64_t same as LONG64
uint8_t same as unsigned char
uint16_t same as unsigned short
uint32_t same as unsigned int
uint64_t same as ULONG64
size_t transient type (not serializable)
float 32 bit float
double 64 bit float
long double extended precision float, use #import "custom/long_double.h"
xsd__decimal <quadmath.h> 128 bit quadruple precision float, use #import "custom/float128.h"
typedef declares a type name, with optional value range and string length bounds
See also
Section numerical types.

List of string types

String Type Notes
char* string (may contain UTF-8 with flag SOAP_C_UTFSTRING)
wchar_t* wide string
std::string C++ string (may contain UTF-8 with flag SOAP_C_UTFSTRING)
std::wstring C++ wide string
char[N] fixed-size string, requires soapcpp2 option -b
_QName normalized QName content
_XML literal XML string content with wide characters in UTF-8
typedef declares a new string type name, may restrict string length
See also
Section string types.

List of date and time types

Date and Time Type Notes
time_t date and time point since epoch
struct tm date and time point, use #import "custom/struct_tm.h"
struct tm date point, use #import "custom/struct_tm_date.h"
struct timeval date and time point, use #import "custom/struct_timeval.h"
unsigned long long time point in microseconds, use #import "custom/long_time.h"
std::chrono::system_clock::time_point date and time point, use #import "custom/chrono_time_point.h"
See also
Section date and time types.

List of time duration types

Time Duration Type Notes
long long duration in milliseconds, use #import "custom/duration.h"
std::chrono::nanoseconds duration in nanoseconds, use #import "custom/chrono_duration.h"
See also
Section time duration types.

List of classes and structs

Classes, Structs, and Members Notes
class C++ class with single inheritance only
struct C struct or C++ struct without inheritance
std::shared_ptr<T> C++11 smart shared pointer
std::unique_ptr<T> C++11 smart pointer
std::auto_ptr<T> C++ smart pointer
std::deque<T> use #import "import/stldeque.h"
std::list<T> use #import "import/stllist.h"
std::vector<T> use #import "import/stlvector.h"
std::set<T> use #import "import/stlset.h"
template<T> class a container with begin(), end(), size(), clear(), and insert() methods
T* data member: pointer to data of type T or points to array of T of size __size
T[N] data member: fixed-size array of type T
union data member: requires a variant selector member __union
void* data member: requires a __type member to indicate the type of object pointed to
See also
Section classes and structs.

List of special classes and structs

Special Classes and Structs Notes
Special Array class/struct single and multidimensional SOAP Arrays
Special Wrapper class/struct complexTypes with simpleContent, wraps __item member
xsd__hexBinary binary content
xsd__base64Binary binary content and optional MIME/MTOM attachments
xsd__anyType DOM elements, use #import "dom.h"
@xsd__anyAttribute DOM attributes, use #import "dom.h"
See also
Section special classes and structs.

Colon notation versus name prefixing with XML tag name translation

To bind C/C++ type names to XSD types, a simple form of name prefixing is used by the gSOAP tools by prepending the XML namespace prefix to the C/C++ type name with a pair of undescrores. This also ensures that name clashes cannot occur when multiple WSDL and XSD files are converted to C/C++. Also, C++ namespaces are not sufficiently rich to capture XML schema namespaces accurately, for example when class members are associated with schema elements defined in another XML namespace and thus the XML namespace scope of the member's name is relevant, not just its type.

However, from a C/C++ centric point of view this can be cumbersome. Therefore, colon notation is an alternative to physically augmenting C/C++ names with prefixes.

For example, the following class uses colon notation to bind the record class to the urn:types schema:

//gsoap ns schema namespace: urn:types
class ns:record // binding 'ns:' to a type name
{
public:
std::string name;
uint64_t SSN;
ns:record *spouse; // using 'ns:' with the type name
ns:record(); // using 'ns:' here too
~ns:record(); // and here
};

The colon notation is stripped away by soapcpp2 when generating the data binding implementation code for our project. So the final code just uses record to identify this class and its constructor/destructor.

When using colon notation make sure to be consistent and not use colon notation mixed with prefixed forms. The name ns:record differs from ns__record, because ns:record is compiled to an unqualified record name.

Colon notation also facilitates overruling the elementFormDefault and attributeFormDefault declaration that is applied to local elements and attributes, when declared as members of classes, structs, and unions. For more details, see qualified and unqualified members.

A C/C++ identifier name (a type name, member name, function name, or parameter name) is translated to an XML tag name by the following rules:

  • Two leading underscores indicates that the identifier name has no XML tag name, i.e. this name is not visible in XML and is not translated.
  • A leading underscore is removed, but the underscore indicates that: a) a struct/class member name or parameter name has a wildcard XML tag name (i.e. matches any XML tag), or b) a type name that has a document root element definition.
  • Trailing underscores are removed (i.e. trailing underscores can be used to avoid name clashes with keywords).
  • Underscores within names are translated to hyphens (hyphens are more common in XML tags).
  • _USCORE is translated to an underscore in the translated XML tag name.
  • _DOT is translated to a dot (.) in the translated XML tag name.
  • _xHHHH is translated to the Unicode character with code point HHHH (hex).
  • C++11 Unicode identifier name characters in UTF-8 are translated as-is.

For example, the C/C++ namespace qualified identifier name s_a__my_way is translated to the XML tag name s-a:my-way by translating the prefix s_a and the local name my_way.

Struct/class member and parameter name translation can be overruled by using backtick XML tags (with gSOAP 2.8.30 and later versions).

C++ Bool and C alternatives

The C++ bool type is bound to built-in XSD type xsd:boolean.

The C alternative is to define an enumeration:

enum xsd__boolean { false_, true_ };

or by defining an enumeration in C with pseudo-scoped enumeration constants:

enum xsd__boolean { xsd__boolean__false, xsd__boolean__true };

The XML value space of these types is false and true, but also accepted are 0 and 1 values for false and true, respectively.

To prevent name clashes, false_ and true_ have an underscore. Trailing underscores are removed from the XML value space.

Enumerations and bitmasks

Enumerations are mapped to XSD simpleType enumeration restrictions of xsd:string, xsd:QName, and xsd:long.

Consider for example:

enum ns__Color { RED, WHITE, BLUE };

which maps to a simpleType restriction of xsd:string in the soapcpp2-generated schema:

<simpleType name="Color">
  <restriction base="xsd:string">
    <enumeration value="RED"/>
    <enumeration value="WHITE"/>
    <enumeration value="BLUE"/>
  </restriction>
</simpleType>

Enumeration name constants can be pseudo-scoped to prevent name clashes, because enumeration name constants have a global scope in C and C++:

enum ns__Color { ns__Color__RED, ns__Color__WHITE, ns__Color__BLUE };

You can also use C++11 scoped enumerations to prevent name clashes:

enum class ns__Color : int { RED, WHITE, BLUE };

Here, the enumeration class base type : int is optional. In place of int in the example above, we can also use int8_t, int16_t, int32_t, or int64_t.

The XML value space of the enumertions defined above is RED, WHITE, and BLUE.

Prefix-qualified enumeration name constants are mapped to simpleType restrictions of xsd:QName, for example:

enum ns__types { xsd__int, xsd__float };

which maps to a simpleType restriction of xsd:QName in the soapcpp2-generated schema:

<simpleType name="types">
  <restriction base="xsd:QName">
    <enumeration value="xsd:int"/>
    <enumeration value="xsd:float"/>
  </restriction>
</simpleType>

Enumeration name constants can be pseudo-numeric as follows:

enum ns__Primes { _3 = 3, _5 = 5, _7 = 7, _11 = 11 };

which maps to a simpleType restriction of xsd:long:

<simpleType name="Color">
  <restriction base="xsd:long">
    <enumeration value="3"/>
    <enumeration value="5"/>
    <enumeration value="7"/>
    <enumeration value="11"/>
  </restriction>
</simpleType>

The XML value space of this type is 3, 5, 7, and 11.

Besides (pseudo-) scoped enumerations, another way to prevent name clashes accross enumerations is to start an enumeration name constant with one underscore or followed it by any number of underscores, which makes it unique. The leading and trailing underscores are removed from the XML value space.

enum ns__ABC { A, B, C };
enum ns__BA { B, A }; // BAD: B = 1 but B is already defined as 2
enum ns__BA_ { B_, A_ }; // OK

The gSOAP soapcpp2 tool permits reusing enumeration name constants across (non-scoped) enumerations as long as these values are assigned the same constant. Therefore, the following is permitted:

enum ns__Primes { _3 = 3, _5 = 5, _7 = 7, _11 = 11 };
enum ns__Throws { _1 = 1, _2 = 2, _3 = 3, _4 = 4, _5 = 5, _6 = 6 };

A bitmask type is an enum* "product" enumeration with a geometric, power-of-two sequence of values assigned to the enumeration constants:

enum* ns__Options { SSL3, TLS10, TLS11, TLS12 };

where the product enum assigns 1 to SSL3, 2 to TLS10, 4 to TLS11, and 8 to TLS12, which allows these enumeration constants to be used in composing bitmasks with | (bitwise or) & (bitwise and), and ~ (bitwise not):

enum ns__Options options = (enum ns__Options)(SSL3 | TLS10 | TLS11 | TLS12);
if (options & SSL3) // if SSL3 is an option, warn and remove from options
{
warning();
options &= ~SSL3;
}

The bitmask type maps to a simpleType list restriction of xsd:string in the soapcpp2-generated schema:

<simpleType name="Options">
  <list>
    <restriction base="xsd:string">
      <enumeration value="SSL3"/>
      <enumeration value="TLS10"/>
      <enumeration value="TLS11"/>
      <enumeration value="TLS12"/>
    </restriction>
  </list>
</simpleType>

The XML value space of this type consists of all 16 possible subsets of the four values, represented by an XML string with space-separated values. For example, the bitmask TLS10 | TLS11 | TLS12 equals 14 and is represented by the XML string TLS10 TLS11 TLS12.

You can also use C++11 scoped enumerations with bitmasks:

enum* class ns__Options { SSL3, TLS10, TLS11, TLS12 };

The base type of a scoped enumeration bitmask, when explicitly given, is ignored. The base type is either int or int64_t, depending on the number of constants enumerated in the bitmask.

To convert enum name constants and bitmasks to a string, we use the auto-generated function for enum T:

const char *soap_T2s(struct soap*, enum T val)

The string returned is stored in an internal buffer of the current soap context, so you MUST copy it to keep it from being overwritten. For example, use char *soap_strdup(struct soap*, const char*).

To convert a string to an enum constant or bitmask, we use the auto-generated function

int soap_s2T(struct soap*, const char *str, enum T *val)

This function takes the name (or names, space-separated for bitmasks) of the enumeration constant in a string str. Names should be given without the pseudo-scope prefix and without trailing underscores. The function sets val to the corresponding integer enum constant or to a bitmask. The function returns SOAP_OK (zero) on success or an error if the string is not a valid enumeration name.

Numerical types

Integer and floating point types are mapped to the equivalent built-in XSD types with the same sign and bit width.

The size_t type is transient (not serializable) because its width is platform dependent. We recommend to use uint64_t instead.

The XML value space of integer types are their decimal representations without loss of precision.

The XML value space of floating point types are their decimal representations. The decimal representations are formatted with the printf format string "%.9G" for floats and the printf format string "%.17lG" for double. To change the format strings, we can assign new strings to the following struct soap context members:

soap.float_format = "%g";
soap.double_format = "%lg";
soap.long_double_format = "%Lg";

Note that decimal representations may result in a loss of precision of the least significant decimal. Therefore, the format strings that are used by default are sufficiently precise to avoid loss, but this may result in long decimal fractions in the XML value space.

The long double extended floating point type requires a custom serializer:

#import "custom/long_double.h"
... use long double ...

You can now use long double, which has a serializer that serializes this type as xsd:decimal. Compile and link your code with custom/long_double.c.

The value space of floating point values includes the special values INF, -INF, and NaN. You can check a value for plus or minus infinity and not-a-number as follows:

soap_isinf(x) && x > 0 // is x INF?
soap_isinf(x) && x < 0 // is x -INF?
soap_isnan(x) // is x NaN?

To assign these values, use:

// x is float // x is double, long double, or __float128
x = FLT_PINFY; x = DBL_PINFTY;
x = FLT_NINFY; x = DBL_NINFTY;
x = FLT_NAN; x = DBL_NAN;

If your system supports __float128 then you can also use this 128 bit floating point type with a custom serializer:

#import "custom/float128.h"
... use xsd__decimal ...

Then use the xsd__decimal alias of __float128, which has a serializer. Do not use __float128 directly, which is transient (not serializable).

To check for INF, -INF, and NaN of a __float128 value use:

isinfq(x) && x > 0 // is x INF?
isinfq(x) && x < 0 // is x -INF?
isnanq(x) // is x NaN?

The range of a typedef-defined numerical type can be restricted using the range : operator with inclusive lower and upper bounds. For example:

typedef int ns__narrow -10 : 10;

This maps to a simpleType restriction of xsd:int in the soapcpp2-generated schema:

<simpleType name="narrow">
  <restriction base="xsd:int">
    <minInclusive value="-10"/>
    <maxInclusive value="10"/>
  </restriction>
</simpleType>

The lower and upper bound of a range are optional. When omitted, values are not bound from below or from above, respectively.

The range of a floating point typedef-defined type can be restricted within floating point constant bounds.

Also with a floating point typedef a printf format pattern can be given of the form "%[width][.precision]f" to format decimal values using the given width and precision fields:

typedef float ns__PH "%5.2f" 0.0 : 14.0;

This maps to a simpleType restriction of xsd:float in the soapcpp2-generated schema:

<simpleType name="PH">
  <restriction base="xsd:float">
    <totalDigits value="5"/>
    <fractionDigits value="2"/>
    <minInclusive value="0"/>
    <maxInclusive value="14"/>
  </restriction>
</simpleType>

For exclusive bounds, we use the < operator instead of the : range operator:

typedef float ns__epsilon 0.0 < 1.0;

Values eps of ns__epsilon are restricted between 0.0 < eps < 1.0.

This maps to a simpleType restriction of xsd:float in the soapcpp2-generated schema:

<simpleType name="epsilon">
  <restriction base="xsd:float">
    <minExclusive value="0"/>
    <maxExclusive value="1"/>
  </restriction>
</simpleType>

To make just one of the bounds exclusive, while keeping the other bound inclusive, we add a < on the left or on the right side of the range ':' operator. For example:

typedef float ns__pos 0.0 < : ; // 0.0 < pos
typedef float ns__neg : < 0.0 ; // neg < 0.0

It is valid to make both left and right side exclusive with < : < which is in fact identical to the exlusive range < operator:

typedef float ns__epsilon 0.0 < : < 1.0; // 0.0 < eps < 1.0

It helps to think of the : as a placeholder of the value between the two bounds, which is easier to memorize than the shorthand forms of bounds from which the : is removed:

Bounds Validation Check Shorthand
1 : 1 <= x 1
1 : 10 1 <= x <= 10
: 10 x <= 10
1 < : < 10 1 < x < 10 1 < 10
1 : < 10 1 <= x < 10
: < 10 x < 10 < 10
1 < : 1 < x 1 <
1 < : 10 1 < x <= 10

Besides float, also double and long double values can be restricted. For example, consider a nonzero probability extended floating point precision type:

#import "custom/long_double.h"
typedef long double ns__probability "%16Lg" 0.0 < : 1.0;

Value range restrictions are validated by the parser for all inbound XML data. A type fault SOAP_TYPE will be thrown by the deserializer if the value is out of range.

Finally, if your system supports __int128_t then you can also use this 128 bit integer type with a custom serializer:

#import "custom/int128.h"
... use xsd__integer ...

Use the xsd__integer alias of __int128_t, which has a serializer. Do not use __int128_t directly, which is transient (not serializable).

To convert numeric values to a string, we use the auto-generated function for numeric type T:

const char *soap_T2s(struct soap*, T val)

For numeric types T, the string returned is stored in an internal buffer of the current soap context, so you MUST copy it to keep it from being overwritten. For example, use char *soap_strdup(struct soap*, const char*).

To convert a string to a numeric value, we use the auto-generated function

int soap_s2T(struct soap*, const char *str, T *val)

where T is for example int, LONG64, float, decimal (the custom serializer name of long double) or xsd__integer (the custom serializer name of __int128_t). The function soap_s2T returns SOAP_OK on success or an error when the value is not numeric. For floating point types, "INF", "-INF" and "NaN" are valid strings to convert to numbers.

String types

String types are mapped to the built-in xsd:string and xsd:QName XSD types.

The wide strings wchar_t* and std::wstring may contain Unicode that is preserved in the XML value space.

Strings char* and std::string can only contain extended Latin, but we can store UTF-8 content that is preserved in the XML value space when the struct soap context is initialized with the flag SOAP_C_UTFSTRING.

Warning
Beware that many XML 1.0 parsers reject all control characters (those between #x1 and #x1F) except for #x9, #xA, and #xD. With the newer XML 1.1 version parsers (including gSOAP) you should be fine.

The length of a string of a typedef-defined string type can be restricted:

typedef std::string ns__password 6 : 16;

which maps to a simpleType restriction of xsd:string in the soapcpp2-generated schema:

<simpleType name="password">
  <restriction base="xsd:string">
    <minLength value="6"/>
    <maxLength value="16"/>
  </restriction>
</simpleType>

String length restrictions are validated by the parser for inbound XML data. A value length fault SOAP_LENGTH will be thrown by the deserializer if the string is too long or too short.

In addition, an XSD regex pattern restriction can be associated with a string typedef:

typedef std::string ns__password "([a-zA-Z]|[0-9]|-)+" 6 : 16;

which maps to a simpleType restriction of xsd:string in the soapcpp2-generated schema:

<simpleType name="password">
  <restriction base="xsd:string">
    <pattern value="([a-zA-Z0-9]|-)+"/>
    <minLength value="6"/>
    <maxLength value="16"/>
  </restriction>
</simpleType>

Pattern restrictions are validated by the parser for inbound XML data only if the soap::fsvalidate and soap::fwvalidate callbacks are defined, see the gSOAP user guide.

Exclusive length bounds can be used with strings:

typedef std::string ns__string255 : < 256; // same as 0 : 255

Fixed-size strings (char[N]) are rare occurrences in the wild, but apparently still used in some projects to store strings. To facilitate fixed-size string serialization, use soapcpp2 option -b. For example:

typedef char ns__buffer[10]; // requires soapcpp2 option -b

which maps to a simpleType restriction of xsd:string in the soapcpp2-generated schema:

<simpleType name="buffer">
  <restriction base="xsd:string">
    <maxLength value="9"/>
  </restriction>
</simpleType>

Note that fixed-size strings MUST contain NUL-terminated text and SHOULD NOT contain raw binary data. Also, the length limitation is more restrictive for UTF-8 content (enabled with the SOAP_C_UTFSTRING) that requires multibyte character encodings. As a consequence, UTF-8 content may be truncated to fit.

Note that raw binary data can be stored in a xsd__base64Binary or xsd__hexBinary structure, or transmitted as a MIME attachment.

The built-in _QName type is a regular C string type (char*) that maps to xsd:QName but has the added advantage that it holds normalized qualified names. There are actually two forms of normalized QName content, to ensure any QName is represented accurately and uniquely:

"prefix:name"
"\"URI\":name"

The first form of string is used when the prefix (and the binding URI) is defined in the namespace table and is bound to a URI (see the .nsmap file). The second form is used when the URI is not defined in the namespace table and therefore no prefix is available to bind and normalize the URI to.

A _QName string may contain a sequence of space-separated QName values, not just one, and all QName values are normalized to the format shown above.

To define a std::string base type for xsd:QName, we use a typedef:

typedef std::string xsd__QName;

The xsd__QName string content is normalized, just as with the _QName normalization.

To serialize strings that contain literal XML content to be reproduced in the XML value space, use the built-in _XML string type, which is a regular C string type (char*) that maps to plain XML CDATA.

To define a std::string base type for literal XML content, use a typedef:

typedef std::string XML;

Strings can hold any of the values of the XSD built-in primitive types. We can use a string typedef to declare the use of the string type as a XSD built-in type:

typedef std::string xsd__token;

You MUST ensure that the string values we populate in this type conform to the XML standard, which in case of xsd:token is the lexical and value spaces of xsd:token are the sets of all strings after whitespace replacement of any occurrence of #x9, #xA , and #xD by #x20 and collapsing.

To copy char* or wchar_t* strings with a context that manages the allocated memory, use functions

char *soap_strdup(struct soap*, const char*)
wchar_t *soap_wstrdup(struct soap*, const wchar_t*)

To convert a wide string to a UTF-8 encoded string, use function

const char* SOAP_FMAC2 soap_wchar2s(struct soap*, const wchar_t *s)

The function allocates and returns a string, with its memory being managed by the context.

To convert a UTF-8 encoded string to a wide string, use function

int soap_s2wchar(struct soap*, const char *from, wchar_t **to, long minlen, long maxlen)

where to is set to point to an allocated wchar_t* string. Pass -1 for minlen and maxlen to ignore length constraints on the target string. The function returns SOAP_OK or an error when the length constraints are not met.

Date and time types

The C/C++ time_t type is mapped to the built-in xsd:dateTime XSD type that represents a date and time within a time zone (typically UTC).

The XML value space contains ISO 8601 Gregorian time instances of the form [-]CCYY-MM-DDThh:mm:ss.sss[Z|(+|-)hh:mm], where Z is the UTC time zone or a time zone offset (+|-)hh:mm] from UTC is used.

A time_t value is considered and represented in UTC by the serializer.

Because the time_t value range is restricted to dates after 01/01/1970 and before 2038 assuming time_t is a long 32 bit, care must be taken to ensure the range of xsd:dateTime values in XML exchanges do not exceed the time_t range.

This restriction does not hold for struct tm (<time.h>), which we can use to store and exchange a date and time in UTC without date range restrictions. The serializer uses the struct tm members directly for the XML value space of xsd:dateTime:

struct tm
{
int tm_sec; // seconds (0 - 60)
int tm_min; // minutes (0 - 59)
int tm_hour; // hours (0 - 23)
int tm_mday; // day of month (1 - 31)
int tm_mon; // month of year (0 - 11)
int tm_year; // year - 1900
int tm_wday; // day of week (Sunday = 0) (NOT USED)
int tm_yday; // day of year (0 - 365) (NOT USED)
int tm_isdst; // is summer time in effect?
char* tm_zone; // abbreviation of timezone (NOT USED)
};

You will lose the day of the week information. It is always Sunday (tm_wday=0) and the day of the year is not set either. The time zone is UTC.

This struct tm type is mapped to the built-in xsd:dateTime XSD type and serialized with the custom serializer custom/struct_tm.h that declares a xsd__dateTime type:

#import "custom/struct_tm.h" // import typedef struct tm xsd__dateTime;
... use xsd__dateTime ...

Compile and link your code with custom/struct_tm.c.

The struct timeval (<sys/time.h>) type is mapped to the built-in xsd:dateTime XSD type and serialized with the custom serializer custom/struct_timeval.h that declares a xsd__dateTime type:

#import "custom/struct_timeval.h" // import typedef struct timeval xsd__dateTime;
... use xsd__dateTime ...

Compile and link your code with custom/struct_timeval.c.

Note that the same value range restrictions apply to struct timeval as they apply to time_t. The added benefit of struct timeval is the addition of a microsecond-precise clock:

struct timeval
{
time_t tv_sec; // seconds since Jan. 1, 1970
suseconds_t tv_usec; // and microseconds
};

A C++11 std::chrono::system_clock::time_point type is mapped to the built-in xsd:dateTime XSD type and serialized with the custom serializer custom/chrono_time_point.h that declares a xsd__dateTime type:

#import "custom/chrono_time_point.h" // import typedef std::chrono::system_clock::time_point xsd__dateTime;
... use xsd__dateTime ...

Compile and link your code with custom/chrono_time_point.cpp.

The struct tm type is mapped to the built-in xsd:date XSD type and serialized with the custom serializer custom/struct_tm_date.h that declares a xsd__date type:

#import "custom/struct_tm_date.h" // import typedef struct tm xsd__date;
... use xsd__date ...

Compile and link your code with custom/struct_tm_date.c.

The XML value space of xsd:date are Gregorian calendar dates of the form [-]CCYY-MM-DD[Z|(+|-)hh:mm] with a time zone.

The serializer ignores the time part and the deserializer only populates the date part of the struct, setting the time to 00:00:00. There is no unreasonable limit on the date range because the year field is stored as an integer (int).

An unsigned long long (ULONG64 or uint64_t) type that contains a 24 hour time in microseconds UTC is mapped to the built-in xsd:time XSD type and serialized with the custom serializer custom/long_time.h that declares a xsd__time type:

#import "custom/long_time.h" // import typedef unsigned long long xsd__time;
... use xsd__time ...

Compile and link your code with custom/long_time.c.

This type represents 00:00:00.000000 to 23:59:59.999999, from 0 to an upper bound of 86,399,999,999. A microsecond resolution means that a 1 second increment requires an increment of 1,000,000 in the integer value.

The XML value space of xsd:time are points in time recurring each day of the form hh:mm:ss.sss[Z|(+|-)hh:mm], where Z is the UTC time zone or a time zone offset from UTC is used. The xsd__time value is always considered and represented in UTC by the serializer.

To convert date and/or time values to a string, we use the auto-generated function for type T:

const char *soap_T2s(struct soap*, T val)

For date and time types T, the string returned is stored in an internal buffer of the current soap context, so you MUST copy it to keep it from being overwritten. For example, use char *soap_strdup(struct soap*, const char*).

To convert a string to a date/time value, we use the auto-generated function

int soap_s2T(struct soap*, const char *str, T *val)

where T is for example dateTime (for time_t), xsd__dateTime (for struct tm, struct timeval, or std::chrono::system_clock::time_point). The function soap_s2T returns SOAP_OK on success or an error when the value is not a date/time.

Time duration types

The XML value space of xsd:duration are values of the form PnYnMnDTnHnMnS where the capital letters are delimiters. Delimiters may be omitted when the corresponding member is not used.

A long long (LONG64 or int64_t) type that contains a duration (time lapse) in milliseconds is mapped to the built-in xsd:duration XSD type and serialized with the custom serializer custom/duration.h that declares a xsd__duration type:

#import "custom/duration.h" // import typedef long long xsd__duration;
... use xsd__duration ...

Compile and link your code with custom/duration.c.

The duration type xsd__duration can represent 106,751,991,167 days forward and backward with millisecond precision.

Durations that exceed a month are always output in days, rather than months to avoid days-per-month conversion inacurracies.

Durations that are received in years and months instead of total number of days from a reference point are not well defined, since there is no accepted reference time point (it may or may not be the current time). The decoder simple assumes that there are 30 days per month. For example, conversion of "P4M" gives 120 days. Therefore, the durations "P4M" and "P120D" are assumed to be identical, which is not necessarily true depending on the reference point in time.

Rescaling of the duration value by may be needed when adding the duration value to a time_t value, because time_t may or may not have a seconds resolution, depending on the platform and possible changes to time_t.

Rescaling is done automatically when you add a C++11 std::chrono::nanoseconds value to a std::chrono::system_clock::time_point value. To use std::chrono::nanoseconds as xsd:duration:

#import "custom/chrono_duration.h" // import typedef std::chrono::duration xsd__duration;
... use xsd__duration ...

Compile and link your code with custom/chrono_duration.cpp.

This type can represent 384,307,168 days (2^63 nanoseconds) forwards and backwards in time in increments of 1 ns (1/1000000000 second).

The same observations with respect to receiving durations in years and months apply to this serializer's decoder.

To convert duration values to a string, we use the auto-generated function

const char *soap_xsd__duration2s(struct soap*, xsd__duration val)

The string returned is stored in an internal buffer, so you MUST copy it to keep it from being overwritten, Use soap_strdup(struct soap*, const char*) for example to copy this string.

To convert a string to a duration value, we use the auto-generated function

int soap_s2xsd__dateTime(struct soap*, const char *str, xsd__dateTime *val)

The function returns SOAP_OK on success or an error when the value is not a duration.

Classes and structs

Classes and structs are mapped to XSD complexTypes. The XML value space consists of XML elements with attributes and subelements, possibly constrained by validation rules that enforce element and attribute occurrence contraints, numerical value range constraints, and string length and pattern constraints.

Classes that are declared with the gSOAP tools are limited to single inheritence only. Structs cannot be inherited.

The class and struct name is bound to an XML namespace by means of the prefix naming convention or by using colon notation:

//gsoap ns schema namespace: urn:types
class ns__record
{
public:
std::string name;
uint64_t SSN;
ns__record *spouse;
ns__record();
~ns__record();
protected:
struct soap *soap;
};

In the example above, we also added a context pointer to the struct soap that manages this instance. It is set when the instance is created in the engine's context, for example when deserialized and populated by the engine.

The class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="name" type="xsd:string" minOccurs="1" maxOccurs="1"/>
    <element name="SSN" type="xsd:unsignedLong" minOccurs="1" maxOccurs="1"/>
    <element name="spouse" type="ns:record" minOccurs="0" maxOccurs="1" nillable="true"/>
  </sequence>
</complexType>

Serializable versus transient types and data members

Public data members of a class or struct are serialized. Private and protected members are transient and not serializable.

Also const and static members are not serializable, with the exception of const char* and const wchar_t*. Types and specific class/struct members can also be made transient with the extern qualifier:

extern class std::ostream; // declare 'std::ostream' transient
class ns__record
{
public:
extern int num; // not serialized
std::ostream out; // not serialized
static const int MAX = 1024; // not serialized
};

By declaring std::ostream transient with extern you can use this type wherever you need it without soapcpp2 complaining that this class is not defined.

Volatile classes and structs

Classes and structs can be declared volatile with the gSOAP tools. This means that they are already declared elsewhere in your project's source code and you do not want soapcpp2 to generate code with a second declaration of these types.

For example, struct tm is declared in <time.h>. You can make it serializable and include a partial list of data members that you want to serialize:

volatile struct tm
{
int tm_sec; // seconds (0 - 60)
int tm_min; // minutes (0 - 59)
int tm_hour; // hours (0 - 23)
int tm_mday; // day of month (1 - 31)
int tm_mon; // month of year (0 - 11)
int tm_year; // year - 1900
};

You can declare classes and structs volatile for any such types you want to serialize by only providing the public data members you want to serialize.

In addition, colon notation is a simple and effective way to bind an existing class or struct to a schema. For example, you can change the tm name as follows without affecting the code that uses struct tm generated by soapcpp2:

volatile struct ns:tm { ... }

This struct maps to a complexType in the soapcpp2-generated schema:

<complexType name="tm">
  <sequence>
    <element name="tm-sec" type="xsd:int" minOccurs="1" maxOccurs="1"/>
    <element name="tm-min" type="xsd:int" minOccurs="1" maxOccurs="1"/>
    <element name="tm-hour" type="xsd:int" minOccurs="1" maxOccurs="1"/>
    <element name="tm-mday" type="xsd:int" minOccurs="1" maxOccurs="1"/>
    <element name="tm-mon" type="xsd:int" minOccurs="1" maxOccurs="1"/>
    <element name="tm-year" type="xsd:int" minOccurs="1" maxOccurs="1"/>
  </sequence>
</complexType>

Mutable classes and structs

Classes and structs can be declared mutable with the gSOAP tools. This means that their definition can be spread out over the source code. This promotes the concept of a class or struct as a row of named values, also known as a named tuple, that can be extended at compile time in your source code with additional members. Because these types differ from the traditional object-oriented principles and design concepts of classes and objects, constructors and destructors cannot be defined (also because we cannot guarantee merging these into one such that all members will be initialized). A default constructor, copy constructor, assignment operation, and destructor will be assigned automatically by soapcpp2.

mutable struct ns__tuple
{
@std::string id;
};
mutable struct ns__tuple
{
std::string name;
std::string value;
};

The members are collected into one definition generated by soapcpp2. Members may be repeated from one definition to another, but only if their associated types are identical. So, for example, a third extension with a value member with a different type fails:

mutable struct ns__tuple
{
float value; // BAD: value is already declared std::string
};

The mutable concept has proven to be very useful when declaring and collecting SOAP Headers for multiple services, which are collected into one struct SOAP_ENV__Header by the soapcpp2 tool.

Default member values in C and C++

Class and struct data members in C and C++ may be declared with an optional default initialization value that is provided "inline" with the declaration of the member:

class ns__record
{
public:
std::string name = "Joe";
...
};

Alternatively, use C++11 default initialization syntax:

class ns__record
{
public:
std::string name { "Joe" };
...
};

These initializations are made by the default constructor that is added by soapcpp2 to each class and struct (in C++ only). A constructor is only added when a default constructor is not already defined with the class declaration.

You can explicitly (re)initialize an object with these initial values by using the soapcpp2 auto-generated functions:

  • void T::soap_default(struct soap*) for class T (C++ only)
  • void soap_default_T(struct soap*, T*) for struct T (C and C++).

Initializations can only be provided for members that have primitive types (bool, enum, time_t, numeric and string types).

See also
Section operations on classes and structs.

Attribute members and backtick XML tags

Class and struct data members are declared as XML attributes by annotating their type with a @ qualifier:

class ns__record
{
public:
@std::string name;
@uint64_t SSN;
ns__record *spouse;
};

This class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="spouse" type="ns:record" minOccurs="0" maxOccurs="1" nillable="true"/>
  </sequence>
  <attribute name="name" type="xsd:string" use="required"/>
  <attribute name="SSN" type="xsd:unsignedLong" use="required"/>
</complexType>

An example XML instance of ns__record is:

<ns:record xmlns:ns="urn:types" name="Joe" SSN="1234567890">
  <spouse name="Jane" SSN="1987654320">
  </spouse>
</ns:record>

Attribute data members are restricted to primitive types (bool, enum, time_t, numeric and string types), xsd__hexBinary, xsd__base64Binary, and custom serializers, such as xsd__dateTime. Custom serializers for types that may be used as attributes MUST define soap_s2T and soap_T2s functions that convert values of type T to strings and back.

Attribute data members can be pointers and smart pointers to these types, which permits attributes to be optional.

The XML tag name of a class/struct member is the name of the member with the usual XML tag translation, see colon notation.

To override the standard translation of identifier names to XML tag names of attributes and elements, add the XML tag name in backticks (requires gSOAP 2.8.30 and later versions):

class ns__record
{
public:
@std::string name `full-name`;
@uint64_t SSN `tax-id`;
ns__record *spouse `married-to`;
};

This class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="married-to" type="ns:record" minOccurs="0" maxOccurs="1" nillable="true"/>
  </sequence>
  <attribute name="full-name" type="xsd:string" use="required"/>
  <attribute name="tax-id" type="xsd:unsignedLong" use="required"/>
</complexType>

An example XML instance of ns__record is:

<ns:record xmlns:ns="urn:types" full-name="Joe" tax-id="1234567890">
  <married-to full-name="Jane" tax-id="1987654320">
  </married-to>
</ns:record>

A backtick XML tag name may contain any non-empty sequence of ASCII and UTF-8 characters except white space and the backtick character. A backtick tag can be combined with member constraints and default member initializers:

@uint64_t SSN `tax-id` 0:1 = 999;

Qualified and unqualified members

Class, struct, and union data members are mapped to namespace qualified or unqualified tag names of local elements and attributes. If a data member has no prefix then the default form of qualification is applied based on the element/attribute form that is declared with the schema of the class, struct, or union type. If the member name has a namespace prefix by colon notation, then the prefix overrules the default (un)qualified form. Therefore, colon notation is an effective mechanism to control qualification of tag names of individual members of classes, structs, and unions.

The XML schema elementFormDefault and attributeFormDefault declarations control the tag name qualification of local elements and attributes, respectively.

  • "unqualified" indicates that local elements/attributes are not qualified with the namespace prefix.
  • "qualified" indicates that local elements/attributes must be qualified with the namespace prefix.

Individual schema declarations of local elements and attributes may overrule this by using the form declaration in a schema and by using colon notation to add namespace prefixes to class, struct, and union members in the header file for soapcpp2.

Consider for example an ns__record class in the ns namespace in which local elements are qualified and local attributes are unqualified by default:

//gsoap ns schema namespace: urn:types
//gsoap ns schema elementForm: qualified
//gsoap ns schema attributeForm: unqualified
class ns__record
{
public:
@std::string name;
@uint64_t SSN;
ns__record *spouse;
};

This class maps to a complexType in the soapcpp2-generated schema with targetNamespace "urn:types", elementFormDefault qualified and attributeFormDefault unqualified:

<schema targetNamespace="urn:types"
  ...
  elementFormDefault="qualified"
  attributeFormDefault="unqualified"
  ...  >
  <complexType name="record">
    <sequence>
      <element name="spouse" type="ns:record" minOccurs="0" maxOccurs="1" nillable="true"/>
    </sequence>
    <attribute name="name" type="xsd:string" use="required"/>
    <attribute name="SSN" type="xsd:unsignedLong" use="required"/>
  </complexType>
</schema>

An example XML instance of ns__record is:

<ns:record xmlns:ns="urn:types" name="Joe" SSN="1234567890">
  <ns:spouse> name="Jane" SSN="1987654320">
  </ns:spouse>
</ns:record>

Note that the root element ns:record is qualified because it is a root element of the schema with target namespace "urn:types". Its local element ns:spouse is namespace qualified because the elementFormDefault of local elements is qualified. Attributes are unqualified.

The default namespace (un)qualification of local elements and attributes can be overruled by adding a prefix to the member name by using colon notation:

//gsoap ns schema namespace: urn:types
//gsoap ns schema elementForm: qualified
//gsoap ns schema attributeForm: unqualified
class ns__record
{
public:
@std::string ns:name; // 'ns:' qualified
@uint64_t SSN;
ns__record *:spouse; // ':' unqualified (empty prefix)
};

The colon notation for member ns:name forces qualification of its attribute tag in XML. The colon notation for member :spouse removes qualification from its local element tag:

<schema targetNamespace="urn:types"
  ...
  elementFormDefault="unqualified"
  attributeFormDefault="unqualified"
  ... >
  <complexType name="record">
    <sequence>
      <element name="spouse" type="ns:record" minOccurs="0" maxOccurs="1" nillable="true" form="unqualified"/>
    </sequence>
    <attribute name="name" type="xsd:string" use="required" form="qualified"/>
    <attribute name="SSN" type="xsd:unsignedLong" use="required"/>
  </complexType>
</schema>

XML instances of ns__record have unqualified spouse elements and qualified ns:name attributes:

<ns:record xmlns:ns="urn:types" ns:name="Joe" SSN="1234567890">
  <spouse> ns:name="Jane" SSN="1987654320">
  </spouse>
</ns:record>

Note that data members can also be prefixed using the prefix__name convention. However, this has a different effect by referring to global (root) elements and attributes, see document root element definitions.

Backtick tag names can be used in place of the member name annotations and will achieve the same effect as described when these tag names are (un)qualified (requires gSOAP 2.8.30 and later versions).

Note
You must declare a target namespace with a //gsoap ns schema namespace: directive to enable the elementForm and attributeForm directives in order to generate valid schemas with soapcpp2. See directives for more details.

Defining document root elements

To define and reference XML document root elements we use type names that start with an underscore:

class _ns__record

Alternatively, we can use a typedef to define a document root element with a given type:

typedef ns__record _ns__record;

This typedef maps to a global root element that is added to the soapcpp2-generated schema:

<element name="record" type="ns:record"/>

An example XML instance of _ns__record is:

<ns:record xmlns:ns="urn:types">
  <name>Joe</name>
  <SSN>1234567890</SSN>
  <spouse>
    <name>Jane</name>
    <SSN>1987654320</SSN>
  </spouse>
</ns:record>

Global-level element/attribute definitions are also referenced and/or added to the generated schema when serializable data members reference these by their qualified name:

typedef std::string _ns__name 1 : 100;
class _ns__record
{
public:
@_QName xsi__type; // built-in XSD attribute xsi:type
_ns__name ns__name; // ref to global ns:name element
uint64_t SSN;
_ns__record *spouse;
};

These types map to the following comonents in the soapcpp2-generated schema:

<simpleType name="name">
  <restriction base="xsd:string">
    <minLength value="1"/>
    <maxLength value="100"/>
  </restriction>
</simpleType>
<element name="name" type="ns:name"/>
<complexType name="record">
  <sequence>
    <element ref="ns:name" minOccurs="1" maxOccurs="1"/>
    <element name="SSN" type="xsd:unsignedLong" minOccurs="1" maxOccurs="1"/>
    <element name="spouse" type="ns:record" minOccurs="0" maxOccurs="1" nillable="true"/>
  </sequence>
  <attribute ref="xsi:type" use="optional"/>
</complexType>
<element name="record" type="ns:record"/>

Use only use qualified member names when their types match the global-level element types that they refer to. For example:

typedef std::string _ns__name; // global element ns:name of type xsd:string
class _ns__record
{
public:
int ns__name; // BAD: global element ns:name is NOT type int
_ns__record ns__record; // OK: ns:record is a global-level root element
...
};

Therefore, we recommend to use qualified member names only when necessary to refer to standard XSD elements and attributes, such as xsi__type, and xsd__lang.

By contrast, colon notation has the desired effect to (un)qualify local tag names by overruling the default element/attribute namespace qualification, see qualified and unqualified members.

As an alternative to prefixing member names, use the backtick tag (requires gSOAP 2.8.30 and later versions):

typedef std::string _ns__name 1 : 100;
class _ns__record
{
public:
@_QName t `xsi:type`; // built-in XSD attribute xsi:type
_ns__name s `ns:name`; // ref to global ns:name element
uint64_t SSN;
_ns__record *spouse;
};

(Smart) pointer members and their occurrence constraints

A public pointer-typed data member is serialized by following its (smart) pointer(s) to the value pointed to. To serialize pointers to dynamic arrays of data, please see the next section on container and array members and their occurrence constraints.

Pointers that are NULL and smart pointers that are empty are serialized to produce omitted element and attribute values, unless an element is required and is nillable.

To control the occurrence requirements of pointer-based data members, occurrence constraints are associated with data members in the form of a range minOccurs : maxOccurs. For non-repeatable (meaning, not a container or array) data members, there are only three reasonable occurrence constraints:

  • 0:0 means that this element or attribute is prohibited.
  • 0:1 means that this element or attribute is optional.
  • 1:1 means that this element or attribute is required.

Pointer-based data members have a default 0:1 occurrence constraint, making them optional, and their XML schema local element/attribute definition is marked as nillable. Non-pointer data members have a default 1:1 occurence constraint, making them required.

A nullptr occurrence constraint may be applicable to required elements that are nillable pointer types, thus nullptr 1:1. This indicates that the element is nillable (can be NULL or nullptr). A pointer data member that is explicitly marked as required and nillable with nullptr 1:1 will be serialized as an element with an xsi:nil attribute, thus effectively revealing the NULL property of its value.

A non-pointer data member that is explicitly marked as optional with 0:1 will be set to its default value when no XML value is presented to the deserializer. A default value can be assigned to data members that have primitive types.

Consider for example:

class ns__record
{
public:
std::shared_ptr<std::string> name; // optional (0:1)
uint64_t SSN 0:1 = 999; // forced this to be optional with default 999
ns__record *spouse 1:1; // forced this to be required (only married people)
};

This class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="name" type="xsd:string" minOccurs="0" maxOccurs="1" nillable="true"/>
    <element name="SSN" type="xsd:unsignedLong" minOccurs="0" maxOccurs="1" default="999"/>
    <element name="spouse" type="ns:record" minOccurs="1" maxOccurs="1" nillable="true"/>
  </sequence>
</complexType>

An example XML instance of ns__record with its name string value set to Joe, SSN set to its default, and spouse set to NULL:

<ns:record xmlns:ns="urn:types" ...>
  <name>Joe</name>
  <SSN>999</SSN>
  <spouse xsi:nil="true"/>
</ns:record>
Note
In general, a smart pointer is simply declared as a volatile template in a gSOAP header file for soapcpp2:
volatile template <class T> class NAMESPACE::shared_ptr;
Note
The soapcpp2 tool generates code that uses NAMESPACE::shared_ptr and NAMESPACE::make_shared to create shared pointers to objects, where NAMESPACE is any valid C++ namespace such as std and boost if you have Boost installed.

Container and array members and their occurrence constraints

Class and struct data member types that are containers std::deque, std::list, std::vector and std::set are serialized as a collection of the values they contain. You can also serialize dynamic arrays, which is the alternative for C to store collections of data. Let's start with STL containers.

You can use std::deque, std::list, std::vector, and std::set containers by importing:

#import "import/stl.h" // import all containers
#import "import/stldeque.h" // import deque
#import "import/stllist.h" // import list
#import "import/stlvector.h" // import vector
#import "import/stlset.h" // import set

For example, to use a vector data mamber to store names in a record:

#import "import/stlvector.h"
class ns__record
{
public:
std::vector<std::string> names;
uint64_t SSN;
};

To limit the number of names in the vector within reasonable bounds, occurrence constraints are associated with the container. Occurrence constraints are of the form minOccurs : maxOccurs:

#import "import/stlvector.h"
class ns__record
{
public:
std::vector<std::string> names 1:10;
uint64_t SSN;
};

This class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="name" type="xsd:string" minOccurs="1" maxOccurs="10"/>
    <element name="SSN" type="xsd:unsignedLong" minOccurs="1" maxOccurs="1""/>
  </sequence>
</complexType>
Note
In general, a container is simply declared as a template in a gSOAP header file for soapcpp2. All class templates are considered containers (except when declared volatile, see smart pointers). For example, std::vector is declared in gsoap/import/stlvector.h as:
template <class T> class std::vector;
Note
You can define and use your own containers. The soapcpp2 tool generates code that uses the following members of the template <typename T> class C container:
void C::clear()
C::iterator C::begin()
C::const_iterator C::begin() const
C::iterator C::end()
C::const_iterator C::end() const
size_t C::size() const
C::iterator C::insert(C::iterator pos, const T& val)
Note
For more details see the example simple_vector container with documentation in the package under gsoap/samples/template.

Because C does not support a container template library, we can use a dynamically-sized array of values. This array is declared as a size-pointer pair of members within a struct or class. The array size information is stored in a special size tag member with the name __size or __sizeX, where X can be any name, or by an $int member to identify the member as a special size tag:

struct ns__record
{
$int sizeofnames; // array size
char* *names; // array of char* names
uint64_t SSN;
};

This class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="name" type="xsd:string" minOccurs="0" maxOccurs="unbounded" nillable="true"/>
    <element name="SSN" type="xsd:unsignedLong" minOccurs="1" maxOccurs="1""/>
  </sequence>
</complexType>

To limit the number of names in the array within reasonable bounds, occurrence constraints are associated with the array size member. Occurrence constraints are of the form minOccurs : maxOccurs:

struct ns__record
{
$int sizeofnames 1:10; // array size 1..10
char* *names; // array of one to ten char* names
uint64_t SSN;
};

This class maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="name" type="xsd:string" minOccurs="1" maxOccurs="10" nillable="true"/>
    <element name="SSN" type="xsd:unsignedLong" minOccurs="1" maxOccurs="1""/>
  </sequence>
</complexType>

Tagged union members

A union member in a class or in a struct cannot be serialized unless a discriminating variant selector member is provided that tells the serializer which union field to serialize. This effectively creates a tagged union.

The variant selector is associated with the union as a selector-union pair of members. The variant selector is a member with the name __union or __unionX, where X can be any name, or by an $int member to identify the member as a variant selector tag:

class ns__record
{
public:
$int xORnORs; // variant selector with values SOAP_UNION_fieldname
union choice
{
float x;
int n;
char *s;
} u;
std::string name;
};

The variant selector values are auto-generated based on the union name choice and the names of its members x, n, and s:

  • xORnORs = SOAP_UNION_choice_x when u.x is valid.
  • xORnORs = SOAP_UNION_choice_n when u.n is valid.
  • xORnORs = SOAP_UNION_choice_s when u.s is valid.
  • xORnORs = 0 when none are valid (should only be used with great care, because XML content validation may fail when content is required but absent).

This class maps to a complexType with a sequence and choice in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <choice>
      <element name="x" type="xsd:float" minOccurs="1" maxOccurs="1"/>
      <element name="n" type="xsd:int" minOccurs="1" maxOccurs="1"/>
      <element name="s" type="xsd:string" minOccurs="0" maxOccurs="1" nillable="true"/>
    </choice>
    <element name="names" type="xsd:string" minOccurs="1" maxOccurs="1" nillable="true"/>
  </sequence>
</complexType>

An STL container or dynamic array of a union requires wrapping the variant selector and union member in a struct:

class ns__record
{
public:
std::vector<
struct ns__data // data with a choice of x, n, or s
{
$int xORnORs; // variant selector with values SOAP_UNION_fieldname
union choice
{
float x;
int n;
char *s;
} u;
}> data; // vector with data
};

and an equivalent definition with a dynamic array instead of a std::vector (you can use this in C with structs):

class ns__record
{
public:
$int sizeOfdata; // size of dynamic array
struct ns__data // data with a choice of x, n, or s
{
$int xORnORs; // variant selector with values SOAP_UNION_fieldname
union choice
{
float x;
int n;
char *s;
} u;
} *data; // points to the data array of length sizeOfdata
};

This maps to two complexTypes in the soapcpp2-generated schema:

<complexType name="data">
  <choice>
    <element name="x" type="xsd:float" minOccurs="1" maxOccurs="1"/>
    <element name="n" type="xsd:int" minOccurs="1" maxOccurs="1"/>
    <element name="s" type="xsd:string" minOccurs="0" maxOccurs="1" nillable="true"/>
  </choice>
</complexType>
<complexType name="record">
  <sequence>
    <element name="data" type="ns:data" minOccurs="0" maxOccurs="unbounded"/>
  </sequence>
</complexType>

The XML value space consists of a sequence of item elements each wrapped in an data element:

<ns:record xmlns:ns="urn:types" ...>
  <data>
    <n>123</n>
  </data>
  <data>
    <x>3.1</x>
  </data>
  <data>
    <s>hello</s>
  </data>
  <data>
    <s>world</s>
  </data>
</ns:record>

To remove the wrapping data element, simply rename the wrapping struct and member to __data to make this member invisible to the serializer with the double underscore prefix naming convention. Also use a dynamic array instead of a STL container (you can use this in C with structs):

class ns__record
{
public:
$int sizeOfdata; // size of dynamic array
struct __data // contains choice of x, n, or s
{
$int xORnORs; // variant selector with values SOAP_UNION_fieldname
union choice
{
float x;
int n;
char *s;
} u;
} *__data; // points to the data array of length sizeOfdata
};

This maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence minOccurs="0" maxOccurs="unbounded">
    <choice>
      <element name="x" type="xsd:float" minOccurs="1" maxOccurs="1"/>
      <element name="n" type="xsd:int" minOccurs="1" maxOccurs="1"/>
      <element name="s" type="xsd:string" minOccurs="0" maxOccurs="1" nillable="true"/>
    </choice>
  </sequence>
</complexType>

The XML value space consists of a sequence of <x>, <n>, and/or <s> elements:

<ns:record xmlns:ns="urn:types" ...>
  <n>123</n>
  <x>3.1</x>
  <s>hello</s>
  <s>world</s>
</ns:record>

Please note that structs, classes, and unions are unnested by soapcpp2 (as in the C standard of nested structs and unions). Therefore, the choice union in the ns__record class is redeclared at the top level despite its nesting within the ns__record class. This means that you will have to choose a unique name for each nested struct, class, and union.

Tagged void pointer members

To serialize data pointed to by void* requires run-time type information that tells the serializer what type of data to serialize by means of a tagged void pointer. This type information is stored in a special type tag member of a struct/class with the name __type or __typeX, where X can be any name, or alternatively by an $int special member of any name as a type tag:

class ns__record
{
public:
$int typeOfdata; // type tag with values SOAP_TYPE_T
void *data; // points to some data of type T
};

A type tag member has nonzero values SOAP_TYPE_T where T is the name of a struct/class or the name of a primitive type, such as int, std__string (for std::string), string (for char*).

This class maps to a complexType with a sequence in the soapcpp2-generated schema:

<complexType name="record">
  <sequence>
    <element name="data" type="xsd:anyType" minOccurs="0" maxOccurs="1"/>
  </sequence>
</complexType>

The XML value space consists of the XML value space of the type with the addition of an xsi:type attribute to the enveloping element:

<ns:record xmlns:ns="urn:types" ...>
  <data xsi:type="xsd:int">123</data>
</ns:record>

This xsi:type attribute is important for the receiving end to distinguish the type of data to instantiate. The receiver cannot deserialize the data without an xsd:type attribute.

You can find the SOAP_TYPE_T name of each serializable type in the auto-generated soapStub.h file.

Also all serializable C++ classes have a virtual int T::soap_type() member that returns their SOAP_TYPE_T value that you can use.

When the void* pointer is NULL or when typeOfdata is zero, the data is not serialized.

An STL container or dynamic array of void* pointers to xsd:anyType data requires wrapping the type tag and void* members in a struct:

class ns__record
{
public:
std::vector<
struct ns__data // data with an xsd:anyType item
{
$int typeOfitem; // type tag with values SOAP_TYPE_T
void *item; // points to some item of type T
}> data; // vector with data
};

and an equivalent definition with a dynamic array instead of a std::vector (you can use this in C with structs):

class ns__record
{
public:
$int sizeOfdata; // size of dynamic array
struct ns__data // data with an xsd:anyType item
{
$int typeOfitem; // type tag with values SOAP_TYPE_T
void *item; // points to some item of type T
} *data; // points to the data array of length sizeOfdata
};

This maps to two complexTypes in the soapcpp2-generated schema:

<complexType name="data">
  <sequence>
    <element name="item" type="xsd:anyType" minOccurs="1" maxOccurs="1" nillable="true"/>
  </sequence>
</complexType>
<complexType name="record">
  <sequence>
    <element name="data" type="ns:data" minOccurs="0" maxOccurs="unbounded"/>
  </sequence>
</complexType>

The XML value space consists of a sequence of item elements each wrapped in a data element:

<ns:record xmlns:ns="urn:types" ...>
  <data>
    <item xsi:type="xsd:int">123</item>
  </data>
  <data>
    <item xsi:type="xsd:double">3.1</item>
  </data>
  <data>
    <item xsi:type="xsd:string">abc</item>
  </data>
</ns:record>

To remove the wrapping data elements, simply rename the wrapping struct and member to __data to make this member invisible to the serializer with the double underscore prefix naming convention. Also use a dynamic array instead of a STL container (you can use this in C with structs):

class ns__record
{
public:
$int sizeOfdata; // size of dynamic array
struct __data // contains xsd:anyType item
{
$int typeOfitem; // type tag with values SOAP_TYPE_T
void *item; // points to some item of type T
} *__data; // points to the data array of length sizeOfdata
};

This maps to a complexType in the soapcpp2-generated schema:

<complexType name="record">
  <sequence minOccurs="0" maxOccurs="unbounded">
    <element name="item" type="xsd:anyType" minOccurs="1" maxOccurs="1"/>
  </sequence>
</complexType>

The XML value space consists of a sequence of data elements:

<ns:record xmlns:ns="urn:types" ...>
  <item xsi:type="xsd:int">123</item>
  <item xsi:type="xsd:double">3.1</item>
  <item xsi:type="xsd:string">abc</item>
</ns:record>

Again, please note that structs, classes, and unions are unnested by soapcpp2 (as in the C standard of nested structs and unions). Therefore, the __data struct in the ns__record class is redeclared at the top level despite its nesting within the ns__record class. This means that you will have to choose a unique name for each nested struct, class, and union.

See also
Section XSD type bindings.

Adding get and set methods

A public get method may be added to a class or struct, which will be triggered by the deserializer. This method will be invoked right after the instance is populated by the deserializer. The get method can be used to update or verify deserialized content. It should return SOAP_OK or set soap::error to a nonzero error code and return it.

A public set method may be added to a class or struct, which will be triggered by the serializer. The method will be invoked just before the instance is serialized. Likewise, the set method should return SOAP_OK or set set soap::error to a nonzero error code and return it.

For example, adding a set and get method to a class declaration:

class ns__record
{
public:
int set(struct soap*); // triggered before serialization
int get(struct soap*); // triggered after deserialization
...
};

To add these and othe rmethods to classes and structs with wsdl2h and typemap.dat, please see class/struct member additions.

Operations on classes and structs

The following functions/macros are generated by soapcpp2 for each type T, which should make it easier to send, receive, and copy XML data in C and in C++:

  • int soap_write_T(struct soap*, T*) writes an instance of T to a file via file descriptor int soap::sendfd) or to a stream via std::ostream *soap::os (C++ only) or saves into a NUL-terminated string by setting const char **soap::os to a string pointer to be set (C only). Returns SOAP_OK on success or an error code, also stored in soap->error.
  • int soap_read_T(struct soap*, T*) reads an instance of T from a file via file descriptor int soap::recvfd) or from a stream via std::istream *soap::is (C++ only) or reads from a NUL-termianted string const char *soap::is (C only). Returns SOAP_OK on success or an error code, also stored in soap->error.
  • void soap_default_T(struct soap*, T*) sets an instance T to its default value, resetting members of a struct to their initial values (for classes we use method T::soap_default, see below).
  • T * soap_dup_T(struct soap*, T *dst, const T *src) (soapcpp2 option -Ec) deep copy src into dst, replicating all deep cycles and shared pointers when a managing soap context is provided as argument. When dst is NULL, allocates space for dst. Deep copy is a tree when argument is NULL, but the presence of deep cycles will lead to non-termination. Use flag SOAP_XML_TREE with managing context to copy into a tree without cycles and pointers to shared objects. Returns dst (or allocated space when dst is NULL).
  • void soap_del_T(const T*) (soapcpp2 option -Ed) deletes all heap-allocated members of this object by deep deletion ONLY IF this object and all of its (deep) members are not managed by a soap context AND the deep structure is a tree (no cycles and co-referenced objects by way of multiple (non-smart) pointers pointing to the same data). Can be safely used after soap_dup(NULL) to delete the deep copy. Does not delete the object itself.

When in C++ mode, soapcpp2 tool adds several methods to classes in addition to adding a default constructor and destructor (when these were not explicitly declared).

The public methods added to a class T:

  • virtual int T::soap_type(void) returns a unique type ID (SOAP_TYPE_T). This numeric ID can be used to distinguish base from derived instances.
  • virtual void T::soap_default(struct soap*) sets all data members to default values.
  • virtual void T::soap_serialize(struct soap*) const serializes object to prepare for SOAP 1.1/1.2 encoded output (or with SOAP_XML_GRAPH) by analyzing its (cyclic) structures.
  • virtual int T::soap_put(struct soap*, const char *tag, const char *type) const emits object in XML, compliant with SOAP 1.1 encoding style, return error code or SOAP_OK. Requires soap_begin_send(soap) and soap_end_send(soap).
  • virtual int T::soap_out(struct soap*, const char *tag, int id, const char *type) const emits object in XML, with tag and optional id attribute and xsi:type, return error code or SOAP_OK. Requires soap_begin_send(soap) and soap_end_send(soap).
  • virtual void * T::soap_get(struct soap*, const char *tag, const char *type) Get object from XML, compliant with SOAP 1.1 encoding style, return pointer to object or NULL on error. Requires soap_begin_recv(soap) and soap_end_recv(soap).
  • virtual void *soap_in(struct soap*, const char *tag, const char *type) Get object from XML, with matching tag and type (NULL matches any tag and type), return pointer to object or NULL on error. Requires soap_begin_recv(soap) and soap_end_recv(soap)
  • virtual T * T::soap_alloc(void) const returns a new object of type T, default initialized and not managed by a soap context.
  • virtual T * T::soap_dup(struct soap*) const (soapcpp2 option -Ec) returns a duplicate of this object by deep copying, replicating all deep cycles and shared pointers when a managing soap context is provided as argument. Deep copy is a tree when argument is NULL, but the presence of deep cycles will lead to non-termination. Use flag SOAP_XML_TREE with the managing context to copy into a tree without cycles and pointers to shared objects.
  • virtual void T::soap_del() const (soapcpp2 option -Ed) deletes all heap-allocated members of this object by deep deletion ONLY IF this object and all of its (deep) members are not managed by a soap context AND the deep structure is a tree (no cycles and co-referenced objects by way of multiple (non-smart) pointers pointing to the same data). Can be safely used after soap_dup(NULL) to delete the deep copy. Does not delete the object itself.

Also for C++, there are four variations of soap_new_T for class/struct/template type T that soapcpp2 auto-generates to create instances on a context-managed heap:

  • T * soap_new_T(struct soap*) returns a new instance of T with default data member initializations that are set with the soapcpp2 auto-generated void T::soap_default(struct soap*) method), but ONLY IF the soapcpp2 auto-generated default constructor is used that invokes soap_default() and was not replaced by a user-defined default constructor.
  • T * soap_new_T(struct soap*, int n) returns an array of n new instances of T. Similar to the above, instances are initialized.
  • T * soap_new_req_T(struct soap*, ...) returns a new instance of T and sets the required data members to the values specified in .... The required data members are those with nonzero minOccurs, see the subsections on (smart) pointer members and their occurrence constraints and container and array members and their occurrence constraints.
  • T * soap_new_set_T(struct soap*, ...) returns a new instance of T and sets the public/serializable data members to the values specified in ....

The above functions can be invoked with a NULL soap context, but we will be responsible to use delete T to remove this instance from the unmanaged heap.

Special classes and structs

SOAP encoded arrays

A class or struct with the following layout is a one-dimensional SOAP encoded Array type:

class ArrayOfT
{
public:
T *__ptr; // array pointer
int __size; // array size
};

where T is the array element type. A multidimensional SOAP Array is:

class ArrayOfT
{
public:
T *__ptr; // array pointer
int __size[N]; // array size of each dimension
};

where N is the constant number of dimensions. The pointer points to an array of __size[0]*__size[1]* ... * __size[N-1] elements.

This maps to a complexType restriction of SOAP-ENC:Array in the soapcpp2-generated schema:

<complexType name="ArrayOfT">
  <complexContent>
    <restriction base="SOAP-ENC:Array">
      <sequence>
        <element name="item" type="T" minOccurs="0" maxOccurs="unbounded" nillable="true"/>
      </sequence>
      <attribute ref="SOAP-ENC:arrayType" WSDL:arrayType="ArrayOfT[]"/>
    </restriction>
  </complexContent>
</complexType>

The name of the class can be arbitrary. We often use ArrayOfT without a prefix to distinguish arrays from other classes and structs.

With SOAP 1.1 encoding, an optional offset member can be added that controls the start of the index range for each dimension:

class ArrayOfT
{
public:
T *__ptr; // array pointer
int __size[N]; // array size of each dimension
int __offset[N]; // array offsets to start each dimension
};

For example, we can define a matrix of floats as follows:

class Matrix
{
public:
double *__ptr;
int __size[2];
};

The following code populates the matrix and serializes it in XML:

soap *soap = soap_new1(SOAP_XML_INDENT);
Matrix A;
double a[6] = { 1, 2, 3, 4, 5, 6 };
A.__ptr = a;
A.__size[0] = 2;
A.__size[1] = 3;
soap_write_Matrix(soap, &A);

Matrix A is serialized as an array with 2x3 values:

<SOAP-ENC:Array SOAP-ENC:arrayType="xsd:double[2,3]" ...>
  <item>1</item>
  <item>2</item>
  <item>3</item>
  <item>4</item>
  <item>5</item>
  <item>6</item>
</SOAP-ENC:Array>

XSD hexBinary and base64Binary types

A special case of a one-dimensional array is used to define xsd:hexBinary and xsd:base64Binary types when the pointer type is unsigned char:

class xsd__hexBinary
{
public:
unsigned char *__ptr; // points to raw binary data
int __size; // size of data
};

and

class xsd__base64Binary
{
public:
unsigned char *__ptr; // points to raw binary data
int __size; // size of data
};

MIME/MTOM attachment binary types

A class or struct with a binary content layout can be extended to support MIME/MTOM (and older DIME) attachments, such as in xop:Include elements:

//gsoap xop schema import: http://www.w3.org/2004/08/xop/include
class _xop__Include
{
public:
unsigned char *__ptr; // points to raw binary data
int __size; // size of data
char *id; // NULL to generate an id, or set to a unique UUID
char *type; // MIME type of the data
char *options; // optional description of MIME attachment
};

Attachments are beyond the scope of this document. The SOAP_ENC_MIME and SOAP_ENC_MTOM context flag must be set to enable attachments. See the gSOAP user guide for more details.

Wrapper class/struct with simpleContent

A class or struct with the following layout is a complexType that wraps simpleContent:

class ns__simple
{
public:
T __item;
};

The type T is a primitive type (bool, enum, time_t, numeric and string types), xsd__hexBinary, xsd__base64Binary, and custom serializers, such as xsd__dateTime.

This maps to a complexType with simpleContent in the soapcpp2-generated schema:

<complexType name="simple">
  <simpleContent>
    <extension base="T"/>
  </simpleContent>
</complexType> 

A wrapper class/struct may include any number of attributes declared with @.

DOM anyType and anyAttribute

Use of a DOM is optional and enabled by #import "dom.h" to use the DOM xsd__anyType element node and xsd__anyAttribute attribute node:

#import "dom.h"
class ns__record
{
public:
@xsd__anyAttribute attributes; // list of DOM attributes
...
xsd__anyType *name; // optional DOM element
};

where name contains XML stored in a DOM node set and attributes is a list of all visibly rendered attributes. The name attributes is arbitrary and any name will suffice.

You should place the xsd__anyType members at the end of the struct or class. This ensures that the DOM members are populated last as a "catch all". A member name starting with double underscore is a wildcard member name and matches any XML tag. These members are placed at the end of a struct or class automatically by soapcpp2.

An #import "dom.h" import is automatically added by wsdl2h with option -d to bind xsd:anyType to DOM nodes, and also to populate xsd:any, xsd:anyAttribute and xsd:mixed XML content:

#import "dom.h"
class ns__record
{
public:
...
@xsd__anyAttribute __anyAttribute; // optional DOM attributes
std::vector<xsd__anyType> __any 0; // optional DOM elements
xsd__anyType __mixed 0; // optional mixed content
};

where the members prefixed with __ are "invisible" to the XML parser, meaning that these members are not bound to XML tag names.

In C you can use a dynamic arrary instead of std::vector:

#import "dom.h"
struct ns__record
{
...
@xsd__anyAttribute __anyAttribute; // optional DOM attributes
$int __sizeOfany; // size of the array
xsd__anyType *__any; // optional DOM elements
xsd__anyType __mixed 0; // optional mixed content
};

Classes can inherit DOM, which enables full use of polymorphism with one base DOM class:

#import "dom.h"
class ns__record : public xsd__anyType
{
...
std::vector<xsd__anyType*> array; // array of objects of any class
};

This permits an xsd__anyType pointer to refer to a derived class such as ns__record, which will be serialized with an xsi:type attribute that is set to "ns:record". The xsi:type attributes add the necessary type information to distinguish the XML content from the DOM base type. This is important for the receiving end: without xsd:type attributes with type names, only base DOM objects are recognized and instantiated.

Because C lacks OOP principles such as class inheritance and polymorphism, you will need to use the special void* members to serialize data pointed to by a void* member.

To ensure that wsdl2h generates pointer-based xsd__anyType DOM nodes with option -d for xsd:any, add the following line to typemap.dat:

xsd__any = | xsd__anyType*

This lets wsdl2h produce class/struct members and containers with xsd__anyType* for xsd:any instead of xsd__anyType. To just force all xsd:anyType uses to be pointer-based, declare in typemap.dat:

xsd__anyType = | xsd__anyType*

If you use wsdl2h with option -p with option -d then every class will inherit DOM as shown above. Without option -d, an xsd__anyType type is generated to serve as the root type in the type hierarchy:

class xsd__anyType { _XML __item; struct soap *soap; };
class ns__record : public xsd__anyType
{
...
};

where the _XML __item member holds any XML content as a literal XML string.

To use the DOM API, compile dom.c (or dom.cpp for C++), or link with -lgsoapssl (or -lgsoapssl++ for C++).

See also
Documentation of XML DOM and XPath for more details.

Directives

You can use //gsoap directives in the gSOAP header file with the data binding interface for soapcpp2. These directives are used to configure the code generated by soapcpp2 by declaring various. properties of Web services and XML schemas. When using the wsdl2h tool, you will notice that wsdl2h generates directives automatically based on the WSDL and XSD input.

Service directives are applicable to service and operations described by WSDL. Schema directives are applicable to types, elements, and attributes defined by XML schemas.

Service directives

A service directive must start at a new line and is of the form:

//gsoap <prefix> service <property>: <value>

where <prefix> is the XML namespace prefix of a service binding. The <property> and <value> fields are one of the following:

Property Value
name name of the service, optionally followed by text describing the service
namespace URI of the WSDL targetNamespace
documentation text describing the service (see also the name property), multiple permitted
doc same as above, shorthand form
style document (default) SOAP messaging style or rpc for SOAP RPC
encoding literal (default), encoded for SOAP encoding, or a custom URI
protocol specifies SOAP or REST, see below
port URL of the service endpoint, usually an http or https address
transport URI declaration of the transport, usually http://schemas.xmlsoap.org/soap/http
definitions name of the WSDL definitions/@name
type name of the WSDL definitions/portType/@name (WSDL2.0 interface/@name)
binding name of the WSDL definitions/binding/@name
portName name of the WSDL definitions/service/port/@name
portType an alias for the type property
interface an alias for the type property
location an alias for the port property
endpoint an alias for the port property

The service name and namespace properties are required in order to generate a valid WSDL with soapcpp2. The other properties are optional.

The style and encoding property defaults are changed with soapcpp2 option -e to rpc and encoded, respectively.

The protocol property is SOAP by default (SOAP 1.1). Protocol property values are:

Protocol Value Description
SOAP SOAP transport, supporting both SOAP 1.1 and 1.2
SOAP1.1 SOAP 1.1 transport (same as soapcpp2 option -1)
SOAP1.2 SOAP 1.2 transport (same as soapcpp2 option -2)
SOAP-GET one-way SOAP 1.1 or 1.2 with HTTP GET
SOAP1.1-GET one-way SOAP 1.1 with HTTP GET
SOAP1.2-GET one-way SOAP 1.2 with HTTP GET
HTTP non-SOAP REST protocol with HTTP POST
POST non-SOAP REST protocol with HTTP POST
GET non-SOAP REST protocol with HTTP GET
PUT non-SOAP REST protocol with HTTP PUT
DELETE non-SOAP REST protocol with HTTP DELETE

You can bind service operations to the WSDL namespace of a service by using the namespace prefix as part of the identifier name of the function that defines the service operation:

int prefix__func(arg1, arg2, ..., argn, result);

You can override the port endpoint URL at runtime in the auto-generated soap_call_prefix__func service call (C/C++ client side) and in the C++ proxy class service call.

Service method directives

Service properties are applicable to a service and to all of its operations. Service method directives are specifically applicable to a service operation.

A service method directive is of the form:

//gsoap <prefix> service method-<property>: <method> <value>

where <prefix> is the XML namespace prefix of a service binding and <method> is the unqualified name of a service operation. The <property> and <value> fields are one of the following:

Method Property Value
method-documentation text describing the service operation
method same as above, shorthand form
method-action "" or URI SOAPAction HTTP header, or URL query string for REST protocols
method-input-action "" or URI SOAPAction HTTP header of service request messages
method-output-action "" or URI SOAPAction HTTP header of service response messages
method-fault-action "" or URI SOAPAction HTTP header of service fault messages
method-header-part member name of the SOAP_ENV__Header struct used in SOAP Header
method-input-header-part member name of the SOAP_ENV__Header struct used in SOAP Headers of requests
method-output-header-part member name of the SOAP_ENV__Header struct used in SOAP Headers of responses
method-fault type name of a struct or class member used in SOAP_ENV__Details struct
method-mime-type REST content type or SOAP MIME attachment content type(s)
method-input-mime-type REST content type or SOAP MIME attachment content type(s) of request message
method-output-mime-type REST content type or SOAP MIME attachment content type(s) of response message
method-style document or rpc
method-encoding literal, encoded, or a custom URI for encodingStyle of messages
method-response-encoding literal, encoded, or a custom URI for encodingStyle of response messages
method-protocol SOAP or REST, see service directives

The method-header-part properties can be repeated for a service operation to declare multiple SOAP Header parts that the service operation requires. You can use method-input-header-part and method-output-header-part to differentiate between request and response messages.

The method-fault property can be repeated for a service operation to declare multiple faults that the service operation may return.

The method-action property serves two purposes:

  1. To set the SOAPAction header for SOAP protocols, i.e. sets the definitions/binding/operation/SOAP:operation/@soapAction.
  2. To set the URL query string for endpoints with REST protocols, i.e. sets the definitions/binding/operation/HTTP:operation/@location, which specifies a URL query string (starts with a ?) to complete the service endpoint URL or extends the endpoint URL with a local path (starts with a /).

Use method-input-action and method-output-action to differentiate the SOAPAction between SOAP request and response messages.

You can always override the port endpoint URL and action values at runtime in the auto-generated soap_call_prefix__func service call (C/C++ client side) and in the auto-generated C++ proxy class service calls. A runtime NULL endpoint URL and/or action uses the defaults set by these directives.

The method-mime-type property serves two purposes:

  1. To set the type of MIME/MTOM attachments used with SOAP protocols. Multiple attachment types can be declared for a SOAP service operation, i.e. adds definitions/binding/operation/input/MIME:multipartRelated/MIME:part/MIME:content/@type for each type specified.
  2. To set the MIME type of a REST operation. This replaces XML declared in WSDL by definitions/binding/operation/(input|output)/MIME:mimeXml with MIME:content/@type. Use application/x-www-form-urlencoded with REST POST and PUT protocols to send encoded form data automatically instead of XML. Only primitive type values can be transmitted with form data, such as numbers and strings, i.e. only types that are legal to use as attributes members.

Use method-input-mime-type and method-output-mime-type to differentiate the attachment types between SOAP request and response messages.

Schema directives

A schema directive is of the form:

//gsoap <prefix> schema <property>: <value>

where <prefix> is the XML namespace prefix of a schema. The <property> and <value> fields are one of the following:

Property Value
namespace URI of the XSD targetNamespace
namespace2 alternate URI for the XSD namespace (i.e. URI is also accepted by the XML parser)
import URI of imported namespace
form unqualified (default) or qualified local element and attribute form defaults
elementForm unqualified (default) or qualified local element form default
attributeForm unqualified (default) or qualified local attribute form default
typed no (default) or yes for serializers to add xsi:type attributes to XML

To learn more about the local form defaults, see qualified and unqualified members.

The typed property is implicitly yes when soapcpp2 option -t is used.

Schema type directives

A schema type directive is of the form:

//gsoap <prefix> schema type-<property>: <name> <value>
//gsoap <prefix> schema type-<property>: <name>::<member> <value>

where <prefix> is the XML namespace prefix of a schema and <name> is an unqualified name of a C/C++ type, and the optional <member> is a class/struct members or enum constant.

You can describe a type:

Type Property Value
type-documentation text describing the schema type
type same as above, shorthand form

For example, you can add a description to an enumeration:

//gsoap ns schema type: Vowels The letters A, E, I, O, U, and sometimes Y
//gsoap ns schema type: Vowels::Y A vowel, sometimes
enum class ns__Vowels : char { A = 'A', E = 'E', I = 'I', O = 'O', U = 'U', Y = 'Y' };

This documented enumeration maps to a simpleType restriction of xsd:string in the soapcpp2-generated schema:

<simpleType name="Vowels">
  <annotation>
    <documentation>The letters A, E, I, O, U, and sometimes Y</documentation>
  </annotation>
  <restriction base="xsd:string">
    <enumeration value="A"/>
    <enumeration value="E"/>
    <enumeration value="I"/>
    <enumeration value="O"/>
    <enumeration value="U"/>
    <enumeration value="Y">
      <annotation>
        <documentation>A vowel, sometimes</documentation>
      </annotation>
    <enumeration/>
  </restriction>
</simpleType>

Serialization rules

A presentation on XML data bindings is not complete without discussing the serialization rules and options that put your data in XML on the wire or store it a file or buffer.

There are several options to choose from to serialize data in XML. The choice depends on the use of the SOAP protocol or if SOAP is not required. The wsdl2h tool automates this for you by taking the WSDL transport bindings into account when generating the service functions in C and C++ that use SOAP or REST.

The gSOAP tools are not limited to SOAP. The tools implement generic XML data bindings for SOAP, REST, and other uses of XML. So you can read and write XML using the serializing operations on classes and structs.

The following sections briefly explain the serialization rules with respect to the SOAP protocol for XML Web services. A basic understanding of the SOAP protocol is useful when developing client and server applications that must interoperate with other SOAP applications.

SOAP/REST Web service client and service operations are represented as functions in your gSOAP header file with the data binding interface for soapcpp2. The soapcpp2 tool will translate these function to client-side service invocation calls and server-side service operation dispatchers.

A discussion of SOAP clients and servers is beyond the scope of this document. However, the SOAP options discussed here also apply to SOAP client and server development.

SOAP document versus rpc style

The wsdl:binding/soap:binding/@style attribute in the wsdl:binding section of a WSDL is either "document" or "rpc". The "rpc" style refers to SOAP RPC (Remote Procedure Call), which is more restrictive than the "document" style by requiring one XML element in the SOAP Body to act as the procedure name with XML subelements as its parameters.

For example, the following directives in the gSOAP header file for soapcpp2 declare that DBupdate is a SOAP RPC encoding service method:

//gsoap ns service namespace: urn:DB
//gsoap ns service method-protocol: DBupdate SOAP
//gsoap ns service method-style: DBupdate rpc
int ns__DBupdate(...);

The XML payload has a SOAP envelope, optional SOAP header, and a SOAP body with one element representing the operation with the parameters as subelements:

<SOAP-ENV:Envelope
  xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
  xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlsn:ns="urn:DB">
  <SOAP-ENV:Body>
    <ns:DBupdate>
      ...
    </ns:DBupdate>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

The "document" style puts no restrictions on the SOAP Body content. However, we recommend that the first element's tag name in the SOAP Body should be unique to each type of operation, so that the receiver can dispatch the operation based on this element's tag name. Alternatively, the HTTP URL path can be used to specify the operation, or the HTTP action header can be used to dispatch operations automatically on the server side (soapcpp2 options -a and -A).

SOAP literal versus encoding

The wsdl:operation/soap:body/@use attribute in the wsdl:binding section of a WSDL is either "literal" or "encoded". The "encoded" use refers to the SOAP encoding rules that support id-ref multi-referenced elements to serialize data as graphs.

SOAP encoding is very useful if the data internally forms a graph (including cycles) and we want the graph to be serialized in XML in a format that ensures that its structure is preserved. In that case, SOAP 1.2 encoding is the best option.

SOAP encoding also adds encoding rules for SOAP arrays to serialize multi-dimensional arrays. The use of XML attributes to exchange XML data in SOAP encoding is not permitted. The only attributes permitted are the standard XSD attributes, SOAP encoding attributes (such as for arrays), and id-ref.

For example, the following directives in the gSOAP header file for soapcpp2 declare that DBupdate is a SOAP RPC encoding service method:

//gsoap ns service namespace: urn:DB
//gsoap ns service method-protocol: DBupdate SOAP
//gsoap ns service method-style: DBupdate rpc
//gsoap ns service method-encoding: DBupdate encoded
int ns__DBupdate(...);

The XML payload has a SOAP envelope, optional SOAP header, and a SOAP body with an encodingStyle attribute for SOAP 1.1 encoding and an element representing the operation with parameters that are SOAP 1.1 encoded:

<SOAP-ENV:Envelope
  xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
  xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlsn:ns="urn:DB">
  <SOAP-ENV:Body SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
    <ns:DBupdate>
      <records SOAP-ENC:arrayType="ns:record[3]">
        <item>
          <name href="#_1"/>
          <SSN>1234567890</SSN>
        </item>
        <item>
          <name>Jane</name>
          <SSN>1987654320</SSN>
        </item>
        <item>
          <name href="#_1"/>
          <SSN>2345678901</SSN>
        </item>
      </records>
    </ns:DBupdate>
    <id id="_1" xsi:type="xsd:string">Joe</id>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Note that the name "Joe" is shared by two records and the string is referenced by SOAP 1.1 href and id attributes.

While gSOAP only introduces multi-referenced elements in the payload when they are actually multi-referenced in the data graph, other SOAP applications may render multi-referenced elements more aggressively. The example could also be rendered as:

<SOAP-ENV:Envelope
  xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
  xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlsn:ns="urn:DB">
  <SOAP-ENV:Body SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
    <ns:DBupdate>
      <records SOAP-ENC:arrayType="ns:record[3]">
        <item href="#id1"/>
        <item href="#id2"/>
        <item href="#id3"/>
      </records>
    </ns:DBupdate>
    <id id="id1" xsi:type="ns:record">
      <name href="#id4"/>
      <SSN>1234567890</SSN>
    </id>
    <id id="id2" xsi:type="ns:record">
      <name href="#id5"/>
      <SSN>1987654320</SSN>
    </id>
    <id id="id3" xsi:type="ns:record">
      <name href="#id4"/>
      <SSN>2345678901</SSN>
    </id>
    <id id="id4" xsi:type="xsd:string">Joe</id>
    <id id="id5" xsi:type="xsd:string">Jane</id>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

SOAP 1.2 encoding is cleaner and produces more accurate XML encodings of data graphs by setting the id attribute on the element that is referenced:

<SOAP-ENV:Envelope
  xmlns:SOAP-ENV="http://www.w3.org/2003/05/soap-envelope"
  xmlns:SOAP-ENC="http://www.w3.org/2003/05/soap-encoding"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlsn:ns="urn:DB">
  <SOAP-ENV:Body>
    <ns:DBupdate SOAP-ENV:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
      <records SOAP-ENC:itemType="ns:record" SOAP-ENC:arraySize="3">
        <item>
          <name SOAP-ENC:id="_1">Joe</name>
          <SSN>1234567890</SSN>
        </item>
        <item>
          <name>Jane</name>
          <SSN>1987654320</SSN>
        </item>
        <item>
          <name SOAP-ENC:ref="_1"/>
          <SSN>2345678901</SSN>
        </item>
      </records>
    </ns:DBupdate>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
Note
Some SOAP 1.2 applications consider the namespace SOAP-ENC of SOAP-ENC:id and SOAP-ENC:ref optional. The gSOAP SOAP 1.2 encoding serialization follows the 2007 standard, while accepting unqualified id and ref attributes.

To remove all rendered id-ref multi-referenced elements in gSOAP, use the SOAP_XML_TREE flag to initialize the gSOAP engine context.

Some XML validation rules are turned off with SOAP encoding, because of the presence of additional attributes, such as id and ref/href, SOAP arrays with arbitrary element tags for array elements, and the occurrence of additional multi-ref elements in the SOAP 1.1 Body.

The use of "literal" puts no restrictions on the XML in the SOAP Body. Full XML validation is possible, which can be enabled with the SOAP_XML_STRICT flag to initialize the gSOAP engine context. However, data graphs will be serialized as trees and cycles in the data will be cut from the XML rendition.

SOAP 1.1 versus SOAP 1.2

There are two SOAP protocol versions: 1.1 and 1.2. The gSOAP tools can switch between the two versions seamlessly. You can declare the default SOAP version for a service operation as follows:

//gsoap ns service method-protocol: DBupdate SOAP1.2

The gSOAP soapcpp2 auto-generates client and server code. At the client side, this operation sends data with SOAP 1.2 but accepts responses also in SOAP 1.1. At the server side, this operation accepts requests in SOAP 1.1 and 1.2 and will return responses in the same SOAP version.

As we discussed in the previous section, the SOAP 1.2 protocol has a cleaner multi-referenced element serialization format that greatly enhances the accuracy of data graph serialization with SOAP RPC encoding and is therefore recommended.

The SOAP 1.2 protocol default can also be set by importing and loading gsoap/import/soap12.h:

#import "soap12.h"

Non-SOAP XML serialization

You can serialize data that is stored on the heap, on the stack (locals), and static data as long as the serializable (i.e. non-transient) members are properly initialized and pointers in the structures are either NULL or point to valid structures. Deserialized data is put on the heap and managed by the gSOAP engine context struct soap, see also memory management.

You can read and write XML directly to a file or stream with the serializing operations on classes and structs.

To define and use XML Web service client and service operations, we can declare these operations in your gSOAP header file with the data binding interface for soapcpp2 as functions. The function are translated by soapcpp2 to client-side service invocation calls and server-side service operation dispatchers.

The REST operations POST, GET, and PUT are declared with //gsoap directives in the gSOAP header file for soapcpp2. For example, a REST POST operation is declared as follows:

//gsoap ns service namespace: urn:DB
//gsoap ns service method-protocol: DBupdate POST
int ns__DBupdate(...);

There is no SOAP Envelope and no SOAP Body in the payload for DBupdate. Also the XML serialization rules are identical to SOAP document/literal. The XML payload only has the operation name as an element with its parameters serialized as subelements:

<ns:DBupdate xmln:ns="urn:DB" ...>
 ...
</ns:DBupdate>

To force id-ref serialization with REST similar to SOAP 1.2 multi-reference encoding, use the SOAP_XML_GRAPH flag to initialize the gSOAP engine context. The XML serialization includes id and ref attributes for multi-referenced elements as follows:

<ns:DBupdate xmln:ns="urn:DB" ...>
  <records>
    <item>
      <name id="_1">Joe</name>
      <SSN>1234567890</SSN>
    </item>
    <item>
      <name>Jane</name>
      <SSN>1987654320</SSN>
    </item>
    <item>
      <name ref="_1"/>
      <SSN>2345678901</SSN>
    </item>
  </records>
</ns:DBupdate>

Input and output

Reading and writing XML from/to files, streams and string buffers is done via the managing context by setting one of the following context members that control IO sources and sinks:

soap->recvfd = fd; // an int file descriptor to read from (0 by default)
soap->sendfd = fd; // an int file descriptor to write to (1 by default)
soap->is = &is; // C++ only: a std::istream is object to read from
soap->os = &os; // C++ only: a std::ostream os object to write to
soap->is = cs; // C only: a const char* string to read from (soap->is will advance)
soap->os = &cs; // C only: pointer to a const char*, will be set to point to the string output

Normally, all of these context members are NULL, which is required to send and receive data over sockets by gSOAP clients and servers. Therefore, if you set any of these context members in a client or server application then you MUST reset them to NULL to ensure that socket communications are not blocked.

Note: the use of soap->is and soap->os in C requires gSOAP 2.8.28 or later.

In the following sections, we present more details on how to read and write to files and streams, and use string buffers as sources and sinks for XML data.

In addition, you can set IO callback functions to handle IO at a lower level.

For more details, see the gSOAP user guide.

Reading and writing from/to files and streams

The default IO is standard input and output. Other sources and sinks (those listed above) will be used until you (re)set them. For example with file-based input and output:

FILE *fp = fopen("record.xml", "r");
if (fp != NULL)
{
soap->recvfd = fileno(fp); // get file descriptor of file to read from
if (soap_read_ns__record(soap, &pers1))
... // handle IO error
fclose(fp);
soap->recvfd = 0; // read from stdin, or -1 to block reading
}
FILE *fp = fopen("record.xml", "w");
if (fp != NULL)
{
soap->sendfd = fileno(fp); // get file descriptor of file to write to
if (soap_write_ns__record(soap, &pers1))
... // handle IO error
fclose(fp);
soap->sendfd = 1; // write to stdout, or -1 to block writing
}

Similar code with streams in C++:

#include <fstream>
std::fstream fs;
fs.open("record.xml", std::ios::in);
if (fs)
{
soap->is = &fs;
if (soap_read__ns__record(soap, &pers1))
... // handle IO error
fs.close();
soap->is = NULL;
}
fs.open("record.xml", std::ios::out);
if (fs)
{
soap->os = &fs;
if (soap_write__ns__record(soap, &pers1))
... // handle IO error
fs.close();
soap->os = NULL;
}

Reading and writing from/to string buffers

For C++ we recommend to use std::stringstream objects from <sstream> as illustrated in the following example:

#include <sstream>
std::stringstream ss;
ss.str("..."); // XML to parse
soap->is = &ss;
if (soap_read__ns__record(soap, &pers1))
... // handle IO error
soap->is = NULL;
soap->os = &ss;
if (soap_write__ns__record(soap, &pers1))
... // handle IO error
soap->os = NULL;
std::string s = ss.str(); // string with XML

For C we can use soap->is and soap->os to point to strings of XML content as follows (this requires gSOAP 2.8.28 or later):

soap->is = "..."; // XML to parse
if (soap_read__ns__record(soap, &pers1))
... // handle IO error
soap->is = NULL;
const char *cs = NULL;
soap->os = &cs;
if (soap_write__ns__record(soap, &pers1))
... // handle IO error
soap->os = NULL;
... = cs; // string with XML (do not free(cs): managed by the context and freed with soap_end())

Note that soap->os is a pointer to a const char* string. The pointer is set by the managing context to point to the XML data that is stored on the context-managed heap.

For earlier gSOAP versions we recommend to use IO callbacks soap->frecv and soap->fsend, see the gSOAP user guide.

Memory management

Memory management with the soap context enables us to allocate data in context-managed heap space that can be collectively deleted. All deserialized data is placed on the context-managed heap by the gSOAP engine.

Memory management in C

When working with gSOAP in C (i.e. using wsdl2h option -c and soapcpp2 option -c), data is allocated on the managed heap with:

  • void *soap_malloc(struct soap*, size_t len).

You can also make shallow copies of data with soap_memdup that uses soap_malloc and a safe version of memcpy to copy a chunk of data src with length len to the context-managed heap:

  • void * soap_memdup(struct soap*, const void *src, size_t len)

This function returns a pointer to the copy. This function requires gSOAP 2.8.27 or later.

In gSOAP 2.8.35 and later, you can use an auto-generated function to allocate and initialize data of type T on the managed heap:

  • T * soap_new_T(struct soap*, int n)

This function returns an array of length n of type T data that is default initialized (by internally calling soap_malloc(soap, n * sizeof(T)) and then soap_default_T(soap, T*) on each array value). Use n=1 to allocate and initialize a single value.

The soap_malloc function is a wrapper around malloc, but which also permits the struct soap context to track all heap allocations for collective deletion with soap_end(soap):

#include "soapH.h"
#include "ns.nsmap"
...
struct soap *soap = soap_new(); // new context
...
struct ns__record *record = (struct ns__record*)soap_malloc(soap, sizeof(struct ns__record));
soap_default_ns__record(soap, record); // auto-generated struct initializer
...
soap_destroy(soap); // only for C++, see section on C++ below
soap_end(soap); // delete record and all other heap allocations
soap_free(soap); // delete context

All data on the managed heap is mass-deleted with soap_end(soap) which must be called before soap_done(soap) or soap_free(soap) (these calls end the use of the soap engine context and free the context, respectively).

The managed heap is checked for memory leaks when the gSOAP code is compiled with -DDEBUG.

The soapcpp2 auto-generated deserializers in C use soap_malloc to allocate and populate deserialized structures, which are managed by the context for collective deletion.

To make char* and wchar_t* string copies to the context-managed heap, we can use the functions:

  • char *soap_strdup(struct soap*, const char *str) and
  • wchar_t *soap_wstrdup(struct soap*, const wchar_t *wstr).

If your C compiler supports typeof then you can use the following macro to simplify the managed heap allocation and initialization of primitive values:

#define soap_assign(soap, lhs, rhs) (*(lhs = (typeof(lhs))soap_malloc(soap, sizeof(*lhs))) = rhs)

Pointers to primitive values are often used for optional members. For example, assume we have the following struct:

struct ns__record
{
const char *name; // required name
uint64_t *SSN; // optional SSN
struct ns__record *spouse; // optional spouse
};

Use soap_assign to create a SSN value on the managed heap:

struct soap *soap = soap_new(); // new context
...
struct ns__record *record = (struct ns__record*)soap_malloc(soap, sizeof(struct ns__record));
soap_default_ns__record(soap, record);
record->name = soap_strdup(soap, "Joe");
soap_assign(soap, record->SSN, 1234567890UL);
...
soap_end(soap); // delete managed soap_malloc'ed heap data
soap_free(soap); // delete context

Without the soap_assign macro, you will need two lines of code, one to allocate and one to assign (you should also use this if your system can run out of memory):

assert((record->SSN = (uint64_t*)soap_malloc(soap, sizeof(utint64_t))) != NULL);
*record->SSN = 1234567890UL;

The gSOAP serializer can serialize any heap, stack, or static allocated data. So we can also create a new record as follows:

struct soap *soap = soap_new(); // new context
...
struct ns__record *record = (struct ns__record*)soap_malloc(soap, sizeof(struct ns__record));
static uint64_t SSN = 1234567890UL;
soap_default_ns__record(soap, record);
record->name = "Joe";
record->SSN = &SSN; // safe to use static values: the value of record->SSN is never changed by gSOAP
...
soap_end(soap); // delete managed soap_malloc'ed heap data
soap_free(soap); // delete context

Use the soapcpp2 auto-generated soap_dup_T functions to duplicate data into another context (this requires soapcpp2 option -Ec to generate), here shown for C with the second argument dst NULL because we want to allocate a new managed structure:

struct soap *other_soap = soap_new(); // another context
struct ns__record *other_record = soap_dup_ns__record(other_soap, NULL, record);
...
soap_destroy(other_soap); // only for C++, see section on C++ below
soap_end(other_soap); // delete other_record and all of its deep data
soap_free(other_soap); // delete context

Note that the only reason to use another context and not to use the primary context is when the primary context must be destroyed together with all of the objects it manages while some of the objects must be kept alive. If the objects that are kept alive contain deep cycles then this is the only option we have, because deep copy with a managing context detects and preserves these cycles unless the SOAP_XML_TREE flag is used with the context:

struct soap *other_soap = soap_new1(SOAP_XML_TREE); // another context
struct ns__record *other_record = soap_dup_ns__record(other_soap, NULL, record);

The resulting deep copy will be a full copy of the source data structure as a tree without co-referenced data (i.e. no digraph) and without cycles. Cycles are pruned and (one of the) pointers that forms a cycle is repaced by NULL.

You can also deep copy into unmanaged space and use the auto-generated soap_del_T() function (requires soapcpp2 option -Ed to generate) to delete it later, but you MUST NOT do this for any data that has deep cycles in its runtime data structure:

struct ns__record *other_record = soap_dup_ns__record(NULL, NULL, record);
...
soap_del_ns__record(other_record); // deep delete record data members
free(other_record); // delete the record

Cycles in the data structure will lead to non-termination when making unmanaged deep copies. Consider for example:

struct ns__record
{
const char *name; // required name
uint64_t SSN; // required SSN
struct ns__record *spouse; // optional spouse
};

The code to populate a structure with a mutual spouse relationship:

struct soap *soap = soap_new();
...
struct ns__record pers1, pers2;
soap_default_ns__record(soap, &pers1);
soap_default_ns__record(soap, &pers2);
pers1.name = "Joe"; // OK to serialize static data
pers1.SSN = 1234567890;
pers1.spouse = &pers2;
pers2.name = soap_strdup(soap, "Jane"); // allocates and copies a string
pers2.SSN = 1987654320;
pers2.spouse = &pers1;
...
struct ns__record *pers3 = soap_dup_ns__record(NULL, NULL, &pers1); // BAD
struct ns__record *pers4 = soap_dup_ns__record(soap, NULL, &pers1); // OK
soap_set_mode(soap, SOAP_XML_TREE);
struct ns__record *pers5 = soap_dup_ns__record(soap, NULL, &pers1); // OK

As we can see, the gSOAP serializer can serialize any heap, stack, or static allocated data, such as in the code above. So we can serialize the stack-allocated pers1 record as follows:

FILE *fp = fopen("record.xml", "w");
if (fp != NULL)
{
soap->sendfd = fileno(fp); // file descriptor to write to
soap_set_mode(soap, SOAP_XML_GRAPH); // support id-ref w/o requiring SOAP
soap_clr_mode(soap, SOAP_XML_TREE); // if set, clear
soap_write_ns__record(soap, &pers1);
fclose(fp);
soap->sendfd = -1; // block further writing
}

which produces an XML document record.xml that is similar to:

<ns:record xmlns:ns="urn:types" id="Joe">
  <name>Joe</name>
  <SSN>1234567890</SSN>
  <spouse id="Jane">
    <name>Jane</name>
    <SSN>1987654320</SSN>
    <spouse ref="#Joe"/>
  </spouse>
</ns:record>

Deserialization of an XML document with a SOAP 1.1/1.2 encoded id-ref graph leads to the same non-termination problem when we later try to copy the data into unmanaged memory heap space:

struct soap *soap = soap_new1(SOAP_XML_GRAPH); // support id-ref w/o SOAP
...
struct ns__record pers1;
FILE *fp = fopen("record.xml", "r");
if (fp != NULL)
{
soap->recvfd = fileno(fp);
if (soap_read_ns__record(soap, &pers1))
... // handle IO error
fclose(fp);
soap->recvfd = -1; // blocks further reading
}
...
struct ns__record *pers3 = soap_dup_ns__record(NULL, NULL, &pers1); // BAD
struct ns__record *pers4 = soap_dup_ns__record(soap, NULL, &pers1); // OK
soap_set_mode(soap, SOAP_XML_TREE);
struct ns__record *pers5 = soap_dup_ns__record(soap, NULL, &pers1); // OK

Copying data with soap_dup_T(soap) into managed heap memory space is always safe. Copying into unmanaged heap memory space requires diligence. But deleting unmanaged data is easy with soap_del_T().

You can also use soap_del_T() to delete structures that you created in C, but only if these structures are created with malloc and do NOT contain pointers to stack and static data.

Finally, when data is allocated in managed memory heap space, either explicitly with the allocation functions shown above or by the gSOAP deserializers, you can delegate the management and deletion of this data to another struct soap context. That context will be responsible to delete the data with soap_end(soap) later:

  • void delegate_deletion(struct soap *soap_from, struct soap *soap_to)

This allows the soap_from context to be deleted with soap_free(soap_from) (assuming it is allocated with soap_new(), use soap_done(soap_from) when soap_from is stack-allocated) while the managed data remains intact. You can use this function any time, to delegate management and deletion to another context soap_to and then continue with the current context. You can also use different source soap_from contexts to delegate management and deletion to the other soap_to context. To mass delete all managed data, use soap_end(soap_to).

Memory management in C++

When working with gSOAP in C++, the gSOAP engine allocates data on a managed heap using soap_new_T(soap) to allocate a type with type name T. Managed heap allocation is tracked by the struct soap context for collective deletion with soap_destroy(soap) for structs, classes, and templates and with soap_end(soap) for everything else.

You should only use soap_malloc(struct soap*, size_t len) to allocate primitive types, but soap_new_T() is preferred. The auto-generated T * soap_new_T(struct soap*) returns data allocated on the managed heap for type T. The data is mass-deleted with soap_destroy(soap) followed by soap_end(soap).

The soap_new_T functions return NULL when allocation fails. C++ exceptions are never raised by gSOAP code when data is allocated, unless SOAP_NOTHROW (set to (std::nothrow)) is redefined to permit new to throw exceptions.

There are four variations of soap_new_T() to allocate data of type T that soapcpp2 auto-generates:

  • T * soap_new_T(struct soap*) returns a new instance of T that is default initialized. For classes, initialization is internally performed using the soapcpp2 auto-generated void T::soap_default(struct soap*) method of the class, but ONLY IF the soapcpp2 auto-generated default constructor is used that invokes soap_default() and was not replaced by a user-defined default constructor.
  • T * soap_new_T(struct soap*, int n) returns an array of n new instances of T. The instances in the array are default initialized as described above.
  • T * soap_new_req_T(struct soap*, ...) (structs and classes only) returns a new instance of T and sets the required data members to the values specified in .... The required data members are those with nonzero minOccurs, see the subsections on (smart) pointer members and their occurrence constraints and container and array members and their occurrence constraints.
  • T * soap_new_set_T(struct soap*, ...) (structs and classes only) returns a new instance of T and sets the public/serializable data members to the values specified in ....

The above functions can be invoked with a NULL soap context, but you are then responsible to use delete T to remove this instance from the unmanaged heap.

For example, to allocate a managed std::string you can use:

std::string *s = soap_new_std__string(soap);

Primitive types and arrays of these are allocated with soap_malloc (soap_new_T calls soap_malloc for primitive type T). All primitive types (i.e. no classes, structs, class templates, containers, and smart pointers) are allocated with soap_malloc for reasons of efficiency.

You can use a C++ template to simplify the managed allocation and initialization of primitive values as follows (this is for primitive types only):

template<class T>
T * soap_make(struct soap *soap, T val)
{
T *p = (T*)soap_malloc(soap, sizeof(T));
if (p) // out of memory? Can also guard with assert(p != NULL) or throw an error
*p = val;
return p;
}

For example, assuming we have the following class:

class ns__record
{
public:
std::string name; // required name
uint64_t *SSN; // optional SSN
ns__record *spouse; // optional spouse
};

You can instantiate a record by using the auto-generated soap_new_set_ns__record and use soap_make to create a SSN value on the managed heap as follows:

soap *soap = soap_new(); // new context
...
ns__record *record = soap_new_set_ns__record(
soap,
"Joe",
soap_make<uint64_t>(soap, 1234567890UL),
NULL);
...
soap_destroy(soap); // delete record and all other managed instances
soap_end(soap); // delete managed soap_malloc'ed heap data
soap_free(soap); // delete context

All data on the managed heap is mass-deleted with soap_destroy(soap) and soap_end(soap) which must be called before soap_done(soap) or soap_free(soap) (these calls end the use of the soap engine context and free the context, respectively).

The managed heap is checked for memory leaks when the gSOAP code is compiled with -DDEBUG.

Note however that the gSOAP serializer can serialize any heap, stack, or static allocated data. So we can also create a new record as follows:

uint64_t SSN = 1234567890UL;
ns__record *record = soap_new_set_ns__record(soap, "Joe", &SSN, NULL);

which will be fine to serialize this record as long as the local SSN stack-allocated value remains in scope when invoking the serializer and/or using record. It does not matter if soap_destroy and soap_end are called beyond the scope of SSN.

To facilitate class methods to access the managing context, we can add a soap context pointer to a class/struct:

class ns__record
{
...
void create_more(); // needs a context to create more internal data
protected:
struct soap *soap; // the context that manages this instance, or NULL
};

The context is set when invoking soap_new_T (and similar) with a non-NULL context argument.

You can also use a template when an array of pointers to values is required. To create an array of pointers to values, define the following template:

template<class T>
T **soap_make_array(struct soap *soap, T* array, int n)
{
T **p = (T**)soap_malloc(soap, n * sizeof(T*));
for (int i = 0; i < n; ++i)
p[i] = &array[i];
return p;
}

The array parameter is a pointer to an array of n values. The template returns an array of n pointers that point to the values in that array:

// create an array of 100 pointers to 100 records
int n = 100;
ns__record **precords = soap_make_array(soap, soap_new_ns__record(soap, n), n);
for (int i = 0; i < n; ++i)
{
precords[i]->name = "...";
precords[i]->SSN = soap_make<uint64_t>(1234567890UL + i);
}

Note that soap_new_ns__record(soap, n) returns a pointer to an array of n records, which is then used to create an array of n pointers to these records.

Use the soapcpp2 auto-generated soap_dup_T functions to duplicate data into another context (this requires soapcpp2 option -Ec to generate), here shown for C++ with the second argument dst NULL to allocate a new managed object:

soap *other_soap = soap_new(); // another context
ns__record *other_record = soap_dup_ns__record(other_soap, NULL, record);
...
soap_destroy(other_soap); // delete record and other managed instances
soap_end(other_soap); // delete other data (the SSNs on the heap)
soap_free(other_soap); // delete context

To duplicate base and derived instances when a base class pointer or reference is provided, use the auto-generated method T * T::soap_dup(struct soap*):

soap *other_soap = soap_new(); // another context
ns__record *other_record = record->soap_dup(other_soap);
...
soap_destroy(other_soap); // delete record and other managed instances
soap_end(other_soap); // delete other data (the SSNs on the heap)
soap_free(other_soap); // delete context

Note that the only reason to use another context and not to use the primary context is when the primary context must be destroyed together with all of the objects it manages while some of the objects must be kept alive. If the objects that are kept alive contain deep cycles then this is the only option we have, because deep copy with a managing context detects and preserves these cycles unless the SOAP_XML_TREE flag is used with the context:

soap *other_soap = soap_new1(SOAP_XML_TREE); // another context
ns__record *other_record = record->soap_dup(other_soap); // deep tree copy

The resulting deep copy will be a full copy of the source data structure as a tree without co-referenced data (i.e. no digraph) and without cycles. Cycles are pruned and (one of the) pointers that forms a cycle is repaced by NULL.

You can also deep copy into unmanaged space and use the auto-generated soap_del_T() function or the T::soap_del() method (requires soapcpp2 option -Ed to generate) to delete it later, but we MUST NOT do this for any data that has deep cycles in its runtime data structure graph:

ns__record *other_record = record->soap_dup(NULL);
...
other_record->soap_del(); // deep delete record data members
delete other_record; // delete the record

Cycles in the data structure will lead to non-termination when making unmanaged deep copies. Consider for example:

class ns__record
{
const char *name; // required name
uint64_t SSN; // required SSN
ns__record *spouse; // optional spouse
};

The code to populate a structure with a mutual spouse relationship:

soap *soap = soap_new();
...
ns__record pers1, pers2;
pers1.name = "Joe";
pers1.SSN = 1234567890;
pers1.spouse = &pers2;
pers2.name = "Jane";
pers2.SSN = 1987654320;
pers2.spouse = &pers1;
...
ns__record *pers3 = soap_dup_ns__record(NULL, NULL, &pers1); // BAD
ns__record *pers4 = soap_dup_ns__record(soap, NULL, &pers1); // OK
soap_set_mode(soap, SOAP_XML_TREE);
ns__record *pers5 = soap_dup_ns__record(soap, NULL, &pers1); // OK

Note that the gSOAP serializer can serialize any heap, stack, or static allocated data, such as in the code above. So we can serialize the stack-allocated pers1 record as follows:

FILE *fp = fopen("record.xml", "w");
if (fp != NULL)
{
soap->sendfd = fileno(fp); // file descriptor to write to
soap_set_mode(soap, SOAP_XML_GRAPH); // support id-ref w/o requiring SOAP
soap_clr_mode(soap, SOAP_XML_TREE); // if set, clear
if (soap_write_ns__record(soap, &pers1))
... // handle IO error
fclose(fp);
soap->sendfd = -1; // block further writing
}

which produces an XML document record.xml that is similar to:

<ns:record xmlns:ns="urn:types" id="Joe">
  <name>Joe</name>
  <SSN>1234567890</SSN>
  <spouse id="Jane">
    <name>Jane</name>
    <SSN>1987654320</SSN>
    <spouse ref="#Joe"/>
  </spouse>
</ns:record>

Deserialization of an XML document with a SOAP 1.1/1.2 encoded id-ref graph leads to the same non-termination problem when we later try to copy the data into unmanaged space:

soap *soap = soap_new1(SOAP_XML_GRAPH); // support id-ref w/o SOAP
...
ns__record pers1;
FILE *fp = fopen("record.xml", "r");
if (fp != NULL)
{
soap->recvfd = fileno(fp); // file descriptor to read from
if (soap_read_ns__record(soap, &pers1))
... // handle IO error
fclose(fp);
soap->recvfd = -1; // block further reading
}
...
ns__record *pers3 = soap_dup_ns__record(NULL, NULL, &pers1); // BAD
ns__record *pers4 = soap_dup_ns__record(soap, NULL, &pers1); // OK
soap_set_mode(soap, SOAP_XML_TREE);
ns__record *pers5 = soap_dup_ns__record(soap, NULL, &pers1); // OK

Copying data with soap_dup_T(soap) into managed space is always safe. Copying into unmanaged space requires diligence. But deleting unmanaged data is easy with soap_del_T().

You can also use soap_del_T() to delete structures in C++, but only if these structures are created with new (and new [] for arrays when applicable) for classes, structs, and class templates and with malloc for anything else, and the structures do NOT contain pointers to stack and static data.

Finally, when data is allocated in managed memory heap space, either explicitly with the allocation functions shown above or by the gSOAP deserializers, you can delegate the management and deletion of this data to another struct soap context. That context will be responsible to delete the data with soap_destroy(soap) and soap_end(soap) later:

  • void delegate_deletion(struct soap *soap_from, struct soap *soap_to)

This allows the soap_from context to be deleted with soap_free(soap_from) (assuming it is allocated with soap_new(), use soap_done(soap_from) when soap_from is stack-allocated) while the managed data remains intact. You can use this function any time, to delegate management and deletion to another context soap_to and then continue with the current context. You can also use different source soap_from contexts to delegate management and deletion to the other soap_to context. To mass delete all managed data, use soap_destroy(soap_to) followed by soap_end(soap_to).

Context flags to initialize the soap struct

There are several context initialization flags and context mode flags to control XML serialization at runtime. The flags are set with soap_new1() to allocate and initialize a new context:

struct soap *soap = soap_new1(<flag> | <flag> ... | <flag>);
,,,
soap_destroy(soap); // delete objects
soap_end(soap); // delete other data and temp data
soap_free(soap); // free context

and with soap_init1() for stack-allocated contexts:

struct soap soap;
soap_init1(&soap, <flag> | <flag> ... | <flag>);
,,,
soap_destroy(&soap); // delete objects
soap_end(&soap); // delete other data and temp data
soap_done(&soap); // clear context

where <flag> is one of:

  • SOAP_C_UTFSTRING: enables all std::string and char* strings to contain UTF-8 content. This option is recommended.
  • SOAP_C_NILSTRING: treat empty strings as if they were NULL pointers, i.e. omits elements and attributes when empty.
  • SOAP_XML_STRICT: strictly validates XML while deserializing. Should not be used together with SOAP 1.1/1.2 encoding style of messaging. Use soapcpp2 option -s to hard code SOAP_XML_STRICT in the generated serializers. Not recommended with SOAP 1.1/1.2 encoding style messaging.
  • SOAP_XML_INDENT: produces indented XML.
  • SOAP_XML_CANONICAL: c14n canonocalization, removes unused xmlns bindings and adds them to appropriate places by applying c14n normalization rules. Should not be used together with SOAP 1.1/1.2 encoding style messaging.
  • SOAP_XML_TREE: write tree XML without id-ref, while pruning data structure cycles to prevent nontermination of the serializer for cyclic structures.
  • SOAP_XML_GRAPH: write graph (digraph and cyclic graphs with shared pointers to objects) using id-ref attributes. That is, XML with SOAP multi-ref encoded id-ref elements. This is a structure-preserving serialization format, because co-referenced data and also cyclic relations are accurately represented.
  • SOAP_XML_DEFAULTNS: uses xmlns default namespace declarations, assuming that the schema attribute form is "qualified" by default (be warned if it is not, since attributes in the null namespace will get bound to namespaces!).
  • SOAP_XML_NIL: emit empty element with xsi:nil for all NULL pointers serialized.
  • SOAP_XML_IGNORENS: the XML parser ignores XML namespaces, i.e. element and attribute tag names match independent of their namespace.
  • SOAP_XML_NOTYPE: removes all xsi:type attribuation. This option is usually not needed unless the receiver rejects all xsi:type attributes. This option may affect the quality of the deserializer, which relies on xsi:type attributes to distinguish base class instances from derived class instances transported in the XML payloads.
  • SOAP_IO_CHUNK: to enable HTTP chunked transfers.
  • SOAP_IO_STORE: full buffering of outbound messages.
  • SOAP_ENC_ZLIB: compress messages, requires compiling with -DWITH_GZIP and linking with zlib (-lz).
  • SOAP_ENC_MIME: enable MIME attachments, see MIME/MTOM attachment binary types.
  • SOAP_ENC_MTOM: enable MTOM attachments, see MIME/MTOM attachment binary types.
Note
C++ Web service proxy and service classes have their own context, either as a base class (soapcpp2 option -i) or as a data member soap that points to a context (soapcpp2 option -j). These contexts are allocated when the proxy or service is instantiated with context flags that are passed to the constructor.

Context parameter settings

After allocation and initializtion of a struct soap context, several context parameters can be set (some parameters may require 2.8.31 and later versions):

  • unsigned int soap::maxlevel is the maximum XML nesting depth levels that the parser permits. Default initialized to SOAP_MAXLEVEL (10000), which is a redefinable macro in stdsoap2.h. Set soap::maxlevel to a lower value to restrict XML parsing nesting depth.
  • long soap::maxlength is the maximum string content length if not already constrained by an XML schema validation maxLength constraint. Zero means unlimited string lengths are permitted (unless restricted by XML schema maxLength). Default initialized to SOAP_MAXLENGTH (0), which is a redefinable macro in stdsoap2.h. Set soap::maxlength to a positive value to restrict the number of (wide) characters in strings parsed, restrict hexBinary byte length, and restrict base64Binary byte length.
  • size_t soap::maxoccurs is the maximum number of array or container elements permitted by the parser. Must be greater than zero (0). Default initialized to SOAP_MAXOCCURS (100000), which is a redefinable macro in stdsoap2.h. Set soap::maxoccurs to a positive value to restrict the number of array and container elements that can be parsed.
  • soap::version is the SOAP version used, with 0 for non-SOAP, 1 for SOAP1.1, and 2 for SOAP1.2. This value is normally set by web service operations, and is otherwise 0 (non-SOAP). Use soap_set_version(struct soap*, short) to set the value. This controls XML namespaces and SOAP id-ref serialization when applicable with an encodingStyle (see below).
  • const char *soap::encodingStyle is a string that is used with SOAP encoding, normally NULL for non-SOAP XML. Set this string to "" (empty string) to enable SOAP encoding style, which supports id-ref graph serialization (see also the SOAP_XML_GRAPH context flag).
  • int soap::recvfd is the file descriptor to read and parse source data from. Default initialized to 0 (stdin). See also input and output.
  • int soap::sendfd is the file descriptor to write data to. Default initialized to 1 (stdout). See also input and output.
  • const char *is for C: string to read and parse source data from, overriding the recvfd source. Normally NULL. This value must be reset to NULL or the parser will continue to read from this string content until the NUL character. See also input and output.
  • std::istream *is for C++: an input stream to read and parse source data from, overriding the recvfd source. Normally NULL. This value must be reset to NULL or the parser will continue to read from this stream until EOF. See also input and output.
  • const char **os for C: points to a string (a const char *) that will be set to point to the string output. Normally NULL. This value must be reset to NULL or the next output will result in reassigning the pointer to point to the next string that is output. The strings are automatically deallocated by soap_end(soap). See also input and output.
  • std::ostream *os for C++: an output stream to write output to. Normally NULL. This value must be reste to NULL or the next output will be send to this stream. See also input and output.

Error handling and reporting

The gSOAP API functions return SOAP_OK (zero) or a non-zero error code. The error code is stored in int soap::error of the current struct soap context. Error messages can be displayed with:

  • void soap_stream_fault(struct soap*, std::ostream &os) for C++ only, prints the error message to an output stream.
  • void soap_print_fault(struct soap*, FILE *fd) prints the error message to a FILE descriptor.
  • void soap_sprint_fault(struct soap*, char *buf, size_t len) saves the error message to a fixed-size buffer allocated with a maximum length.
  • void soap_print_fault_location(struct soap*, FILE *fd) prints the location and part of the XML where the parser encountered an error.

C++ exceptions are never raised by gSOAP code, even when data is allocated. (That is unless the SOAP_NOTHROW macro (set to (std::nothrow) by default) is redefined to permit new to throw exceptions.)

A SOAP_EOM error code is returned when memory was exhausted during processing of input and/or output of data.

An EOF (SOAP_EOF or -1) error code is returned when the parser has hit EOF but expected more input, or when socket communications timed out. In addition to the SOAP_EOF error, the int soap::errnum of the struct soap context is set to the errno value of the operation that failed. For timeouts, the soap::ernum value is always 0 instead of an errno error code.

Use soap_xml_error_check(soap->error) to check for XML errors. This returns true (non-zero) when a parsing and validation error has occurred.

For example:

#include <sstream>
struct soap *soap = soap_new1(SOAP_XML_INDENT | SOAP_XML_STRICT | SOAP_XML_TREE);
struct ns__record person;
std::stringstream ss;
ss.str("..."); // XML to parse
soap->is = &ss;
if (soap_read__ns__record(soap, &person))
{
if (soap_xml_error_check(soap->error))
std::cerr << "XML parsing error!" << std::endl;
else
soap_stream_fault(soap, std::cerr);
}
else
{
... // all OK, use person record
}
soap_destroy(soap); // delete objects
soap_end(soap); // delete other data and temp data
soap_free(soap); // free context

When deploying your application on UNIX and Linux systems, UNIX signal handlers should be added to your code handle signals, in particular SIGPIPE:

signal(SIGPIPE, sigpipe_handler);

where the sigpipe_handler is a function:

void sigpipe_handler(int x) { }

Other UNIX signals may have to be handled as well.

The gSOAP engine is designed for easy memory cleanup after being interrupted. Use soap_destroy(soap) and soap_end(soap), after which the soap context can be reused.

Features and limitations

In general, to use the generated code:

  • Make sure to #include "soapH.h" in your code and also define a namespace table or #include "ns.nsmap" with the generated table, where ns is the namespace prefix for services.
  • Use soapcpp2 option -j (C++ only) to generate C++ proxy and service objects. The auto-generated files include documented inferfaces. Compile with soapC.cpp and link with -lgsoap++, or alternatively compile stdsoap2.cpp.
  • Without soapcpp2 option -j: client-side uses the auto-generated soapClient.cpp and soapC.cpp (or C versions of those). Compile and link with -lgsoap++ (-lgsoap for C), or alternatively compile stdsoap2.cpp (stdsoap2.c for C).
  • Without soapcpp2 option -j: server-side uses the auto-generated soapServer.cpp and soapC.cpp (or C versions of those). Compile and link with -lgsoap++ (-lgsoap for C), or alternatively compile stdsoap2.cpp (stdsoap2.c for C).
  • Use soap_new() or soap_new1(int flags) to allocate and initialize a heap-allocated context with or without flags. Delete this context with soap_free(struct soap*), but only after soap_destroy(struct soap*) and soap_end(struct soap*).
  • Use soap_init(struct *soap) or soap_init1(struct soap*, int flags) to initialize a stack-allocated context with or without flags. End the use of this context with soap_done(struct soap*), but only after soap_destroy(struct soap*) and soap_end(struct soap*).

Additional notes with respect to the wsdl2h and soapcpp2 tools:

  • Nested classes, structs, and unions in a gSOAP header file are unnested by soapcpp2.
  • Use #import "file.h" instead of #include to import other header files in a gSOAP header file for soapcpp2. The #include, #define, and #pragma are accepted by soapcpp2, but are moved to the very start of the generated code for the C/C++ compiler to include before all generated definitions. Often it is useful to add an #include with a volatile type that includes the actual type declaration, and to ensure transient types are declared when these are used in a data binding interface declared in a gSOAP header file for soapcpp2.
  • To remove any SOAP-specific bindings, use soapcpp2 option -0.
  • A gSOAP header file for soapcpp2 should not include any code statements, only data type declarations. This includes constructor initialization lists that are not permitted. Use member initializations instead.
  • C++ namespaces are supported. Use wsdl2h option -qname. Or add a namespace name { ... } to the header file, but the { ... } MUST cover the entire header file content from begin to end.
  • Optional XML DOM support can be used to store mixed content or literal XML content. Otherwise, mixed content may be lost. Use wsdl2h option -d for XML DOM support and compile and link with dom.c or dom.cpp. For details, see XML DOM and XPath.

Removing SOAP namespaces from XML payloads

The soapcpp2 tool generates a .nsmap file that includes two bindings for SOAP namespaces. We can remove all SOAP namespaces (and SOAP processing logic) with soapcpp2 option -0 or by simply setting the two entries to NULL:

struct Namespace namespaces[] =
{
{"SOAP-ENV", NULL, NULL, NULL},
{"SOAP-ENC", NULL, NULL, NULL},
...
};

Note that once the .nsmap is generated, you can copy-paste the content into your project code. However, if we rerun wsdl2h on updated WSDL/XSD files or typemap.dat declarations then we need to use the updated table.

In cases that no XML namespaces are used at all, for example with XML-RPC, you may use an empty namespace table:

struct Namespace namespaces[] = {{NULL,NULL,NULL,NULL}};

However, beware that any built-in xsi attributes that are rendered will lack the proper namespace binding. At least we suggest to use SOAP_XML_NOTYPE for this reason.

Examples

Select the project files below to peruse the source code examples.

Source files

  • address.xsd Address book schema
  • address.cpp Address book app (reads/writes address.xml file)
  • addresstypemap.dat Schema namespace prefix name preference for wsdl2h
  • graph.h Graph data binding (tree, digraph, cyclic graph)
  • graph.cpp Test graph serialization as tree, digraph, and cyclic

Generated files

  • address.h gSOAP-specific data binding definitions from address.xsd
  • addressStub.h C++ data binding definitions
  • addressH.h Serializers
  • addressC.cpp Serializers
  • address.xml Address book data generated by address app
  • graphStub.h C++ data binding definitions
  • graphH.h Serializers
  • graphC.cpp Serializers
  • g.xsd XSD schema with g:Graph complexType
  • g.nsmap xmlns bindings namespace mapping table

Build steps

Building the AddressBook example:

wsdl2h -g -t addresstypemap.dat address.xsd
soapcpp2 -0 -CS -I../../import -p address address.h
c++ -I../.. address.cpp addressC.cpp -o address -lgsoap++

Option -g produces bindings for global (root) elements in addition to types. In this case the root element a:address-book is bound to _a__address_book. The complexType a:address is bound to class a__address, which is also the type of _a__address_book. This option is not required, but allows you to use global element tag names when referring to their serializers, instead of their type name. Option -0 removes the SOAP protocol. Options -C and -S removes client and server code generation. Option -p renames the output soap files to address files.

See the address.cpp implementation and related pages.

The addresstypemap.dat file specifies the XML namespace prefix for the bindings:

#       Bind the address book schema namespace to prefix 'a'

a = "urn:address-book-example"

#       By default the xsd:dateTime schema type is translated to time_t
#       To map xsd:dateTime to struct tm, enable the following line:

# xsd__dateTime = #import "../../custom/struct_tm.h"

#       ... and compile/link with custom/struct_tm.c

The DOB field is a xsd:dateTime, which is bound to time_t by default. To change this to struct tm, enable the import of the xsd__dateTime custom serializer by uncommenting the definition of xsd__dateTime in addresstypemap.dat. Then change soap_dateTime2s to soap_xsd__dateTime2s in the code.

Building the graph serialization example:

soapcpp2 -CS -I../../import -p graph graph.h
c++ -I../.. graph.cpp graphC.cpp -o graph -lgsoap++

To compile without using the libgsoap++ library: simply compile stdsoap2.cpp together with the above.

Usage

To execute the AddressBook example:

./address

To execute the Graph serialization example:

./graph