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This is a detailed overview of the gSOAP XML data bindings concepts and implementation. At the end of this document two examples are given to illustrate the application of 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 XML is serialized as a tree, digraph, and cyclic graph. The digraph and cyclic graph serialization rules are similar to SOAP 1.1/1.2 encoded multi-ref elements with id-ref attributes to link elements through IDREF XML references, creating a an XML graph with pointers to XML nodes.
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, which we will explain in the next sections. Support for XML schema components is practically 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 higher, which supports C++11 features. However, C++11 is not required to use this material and follow the example, 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. van Engelen at the Florida State University (the project was named "stub/skeleton compiler"). The first articles on 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.
To convert WSDL and XML schemas (XSD files) to code, we first use the wsdl2h command to generate the data binding interface code that is saved to a special gSOAP header file:
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 a data binding interface file file.h
that uses familar C/C++ syntax extended with gsoap
directives and includes notational conventions to declare C/C++ types and functions that are associated with these bindings.
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 and mapping C/C++ to XML 1.0/1.1 and XSD 1.0/1.1. This covers all of the following standard XSD components with their optional [ attributes ]
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 components:
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:
enumeration maps to enum simpleContent maps to class/struct wrapper with __item member complexContent maps to class/struct list maps to enum* bitmask (enum* enumerates up to 64 bit masks) extension through inheritance restriction partly through inheritance and redeclaration length restricts content length minLength restricts content length maxLength restricts content length minInclusive restricts numerical value range maxInclusive restricts numerical value range minExclusive restricts numerical value range maxExclusive restricts numerical value range precision maps to float/double but constraint is not validated scale maps to float/double but constraint is not validated totalDigits maps to float/double but constraint is not validated fractionDigits maps to float/double but constraint is not validated pattern must define soap::fsvalidate callback to validate patterns union maps to string of values
All primitive XSD types are supported, including but not limited to the following XSD types:
anyType maps to _XML string with literal XML content (or DOM with wsdl2h option -d) anyURI maps to string string maps to string (char*/wchar_t*/std::string/std::wstring) boolean maps to bool (C++) or enum xsd__boolean (C) byte maps to char (int8_t) short maps to short (int16_t) int maps to int (int32_t) long maps to LONG64 (long long and int64_t) unsignedByte maps to unsigned char (uint8_t) unsignedShort maps to unsigned short (uint16_t) unsignedInt maps to unsigned int (uint32_t) unsignedLong maps to ULONG64 (unsigned long long and uint64_t) float maps to float double maps to double integer maps to string or #import "custom/int128.h" decimal maps to string or #import "custom/long_double.h" precisionDecimal maps to string duration maps to string or #import "custom/duration.h" dateTime maps to time_t or #import "custom/struct_tm.h" time maps to string or #import "custom/long_time.h" date maps to string or #import "custom/struct_tm_date.h" hexBinary maps to class/struct xsd__hexBinary base64Bianry maps to class/struct xsd__base64Binary QName maps to _QName (URI normalization rules are applied)
All other primitive XSD types not listed above are mapped to strings, by generating a typedef. For example, xsd:token is bound to a C++ or C string, which associates a value space to the type with the appropriate XSD type name used by the soapcpp2-generated serializers:
typedef std::string xsd__token; // C++ typedef char *xsd__token; // C (wsdl2h option -c)
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.
We 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.
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:
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 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.
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).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 field, because xsd__duration
is the name that wsdl2h uses to identify and use this type for our code. The third field 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 field is empty, because wchar_t
is a C type and does not need to be declared. A ptruse
field is given so that we do not end up generating the wrong pointer types, such as wchar_t**
and std::shared_ptr<wchar_t>
.
When the auto-generated declaration should be preserved but the use
or ptruse
fields 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*
are used to (de)serialize any data type, including base and its derived 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.
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
.
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
we should also 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 ;
__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;
SOAP_TYPE
or SOAP_LENGTH
will be thrown by the deserializer if the value is out of range.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"
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.
The wsdl2h tool maps xsd:dateTime to time_t
by default.
The trouble with time_t
is that it is limited to dates between 1970 and 2038 (until its decided by 2038 to widen the bit representation of time_t
).
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. You could even map xsd:dateTime to a plain string (use char*
with C and std::string
with C++). For example:
xsd__dateTime = | char*
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
).
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.
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.
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.
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.
short
by int
and float
by double
).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.
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
.
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"
directive 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.
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 we can also declare one ourself. If so, we add gSOAP directives and declare in this file all our C/C++ types we want to serialize in XML. We can also declare functions that will be converted to service operations by soapcpp2.
Global function declarations define service operations, which are of the form:
int ns__name(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.
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.
bool C++ bool enum xsd__boolean C alternative bool
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)
char byte short 16 bit integer int 32 bit integer long 32 bit integer LONG64 64 bit integer xsd__integer 128 bit __int128_t 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 __float128 quadruple precision float, use #import "custom/float128.h" typedef declares a type name, with optional value range and string length bounds
char* string wchar_t* wide string std::string C++ string std::wstring C++ wide string char[N] fixed-size string, requires soapcpp2 option -b _QName normalized QName content _XML literal XML string content typedef declares a type name, may restrict string length
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"
long long duration in milliseconds, use #import "custom/duration.h" std::chrono::nanoseconds duration in nanoseconds, use #import "custom/chrono_duration.h"
class C++ class with single inheritance only struct C struct or C++ struct without inheritance T* pointer to type T T[N] fixed-size array of type T 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 union requires a discriminant member void* requires a __type member to indicate the type of object pointed to
Array single and multidimensional SOAP Arrays xsd__hexBinary binary content xsd__base64Binary binary content and optional MIME/MTOM attachments Wrapper complexTypes with simpleContent
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 we have 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.
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 accepts 0
and 1
as values.
To prevent name clashes, false_
and true_
have an underscore which are removed in the XML value space.
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 };
We 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 in 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 in by the XML string TLS10 TLS11 TLS12
.
We 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)
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.
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 ...
We 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, so you MUST copy it to keep it from being overwritten. For example, use 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 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 XML_C_UTFSTRING
.
#x1
and #x1F
) except #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 for more details.
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
where the first form 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;
We 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.
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, 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 86399999999
. A microsecond resolution means that a 1 second increment requires an increment of 1000000 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, so you MUST copy it to keep it from being overwritten. For example, use 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.
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 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 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>
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 be made transient by using 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 we can use this type where we need it and without soapcpp2 complaining that this class is not defined.
Classes and structs can be declared volatile
with the gSOAP tools. This means that they are already declared elsewhere in our project's source code. We do not want soapcpp2 to generate a second definition for these types.
For example, struct tm
is declared in <time.h>
. We want it serializable and serialize only a selection of its data members:
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 };
We can declare classes and structs volatile
for any such types we want to serialize by only providing the public data members we want to serialize.
Colon notation comes in handy to bind an existing class or struct to a schema. For example, we 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>
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 our 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.
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";
These initializations are made by the default constructor that is added by soapcpp2 to each class and struct. 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 the auto-generated soap_default(struct soap*)
method of a class and the auto-generated soap_default_T(struct soap*, T*)
function for a struct T
in C and C++.
Initializations can only be provided for members that have primitive types (bool
, enum
, time_t
, numeric and string types).
Class and struct data members can be declared as XML attributes by annotating their type with a @
with the declaration of the member:
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</name> <SSN>1987654320</SSN> </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.
A public pointer-typed data member is serialized by following its (smart) pointer(s) to the value pointed to.
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 XSD schema local element/attribute definition is marked as nillable. Non-pointer data members have a default 1:1
occurence constraint, making them required.
A pointer data member that is explicitly marked as required with 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>
volatile
template in a gSOAP header file for soapcpp2: volatile template <class T> class NAMESPACE::shared_ptr;
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.Class and struct data member types that are containers std::deque
, std::list
, std::vector
and std::set
are serialized as a collections of values.
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>
volatile
, see smart pointers). For example, std::vector
is declared in gsoap/import/stlvector.h
as: template <class T> class std::vector;
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)
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 member pair:
struct ns__record { $int sizeofnames; // array size char* *names; // array of char* names uint64_t SSN; };
where the marker $
with int
denotes a special type that is used to store the array size and to indicate that this is a size-pointer member pair that declares a dynamically-sized array.
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>
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 member pair, where the variant selector is a special $int
member:
class ns__record { public: $int xORnORs; // variant selector 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="10" nillable="true"/> </sequence> </complexType>
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.
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"/>
class _ns__record { public: int ns__name; // BAD: element ns:name is NOT of an int type
xsi__type
, and xsd__lang
. The soapcpp2 tool does not prevent abuse of this mechanism.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 *soap::sendfd)
) or to a stream (via std::ostream *soap::os
). 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 *soap::recvfd)
) or from a stream (via std::istream *soap::is
). 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 and structs, in addition to adding a default constructor and destructor (when these were not explicitly declared).
The public methods added to a class/struct 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.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>
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 };
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 and we refer to the gSOAP user guide for more details.
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 @
.
A presentation on XML data bindings is not complete without discussing the serialization rules that put your data in XML on the wire.
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 our gSOAP header file 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.
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).
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](toxsd10) 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>
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.
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"
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 our gSOAP header file for soapcpp2 as functions that soapcpp2 will translate in client-side service invocation calls and server-side service operation dispatchers. These functions are auto-generated by wsdl2h from WSDLs. Note that XSDs do not include service definitions.
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>
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.
In C (wsdl2h option -c
and soapcpp2 option -c
), the gSOAP engine allocates data on a context-managed heap with:
void *soap_malloc(struct soap*, size_t len)
.The soap_malloc
function is a wrapper around malloc
, but which also allows 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 = soap_malloc(soap, sizeof(struct ns__record)); soap_default_ns__record(soap, record); ... 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
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*)
andwchar_t *soap_wstrdup(struct soap*, const wchar_t*)
.We 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.
We 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 we MUST NOT do this for any data that we suspect has deep cycles:
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; uint64_t SSN; ns__record *spouse; };
Our 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 our code above. So we can serialize the stack-allocated pers1
record as follows:
soap->sendfd = fopen("record.xml", "w"); 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(soap->sendfd); soap->sendfd = NULL;
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:
struct soap *soap = soap_new1(SOAP_XML_GRAPH); // support id-ref w/o SOAP ... struct ns__record pers1; soap->recvfd = fopen("record.xml", "r"); soap_read_ns__record(soap, &pers1); fclose(soap->recvfd); soap->recvfd = NULL; ... 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 space is always safe. Copying into unmanaged space requires diligence. But deleting unmanaged data is easy with soap_del_T()
.
We can also use soap_del_T()
to delete structures that we created in C, but only if these structures are created with malloc
and do NOT contain pointers to stack and static data.
In C++, the gSOAP engine allocates data on a managed heap using a combination of void *soap_malloc(struct soap*, size_t len)
and soap_new_T()
, where T
is the name of a class, struct, or class template (container or smart pointer). Heap allocation is tracked by the struct soap
context for collective deletion with soap_destroy(soap)
and soap_end(soap)
.
Only structs, classes, and class templates are allocated with new
via soap_new_T(struct soap*)
and mass-deleted with soap_destroy(soap)
.
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 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.
Primitive types and arrays of these are allocated with soap_malloc
by the gSOAP engine. As we stated above, all types except for classes, structs, class templates (containers and smart pointers) are allocated with soap_malloc
for reasons of efficiency.
We can use a C++ template to simplify the managed allocation and initialization of primitive values as follows (this is for primitive types only, because we should allocate structs and classes with soap_new_T
):
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 };
We can instantiate a record by using the auto-generated soap_new_set_ns__record
and our soap_make
to create a SSN value on the managed heap:
soap *soap = soap_new(); // new context ... ns__record *record = soap_new_set_ns__record( soap, "Joe", soap_make<uint64_t>(soap, 1234567890LL), 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
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 = 1234567890LL; 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 our 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.
We 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 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.
We 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 we suspect has deep cycles:
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; uint64_t SSN; ns__record *spouse; };
Our 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 our code above. So we can serialize the stack-allocated pers1
record as follows:
soap->sendfd = fopen("record.xml", "w"); 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(soap->sendfd); soap->sendfd = NULL;
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; soap->recvfd = fopen("record.xml", "r"); soap_read_ns__record(soap, &pers1); fclose(soap->recvfd); soap->recvfd = NULL; ... 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()
.
We 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.
In general, to use the generated code:
#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.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*)
.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*)
.There are several context initialization flags and context mode flags to control XML serialization at runtime:
SOAP_C_UTFSTRING
: enables all std::string
and char*
strings to contain UTF-8 content. This option is recommended.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 bindings, assuming that the schema element form is "qualified" by default (be warned if it is not!).SOAP_XML_NOTYPE
: removes all xsi:type attribuation. This option is usually not needed unless the receiver rejects all xs: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.Additional notes with respect to the wsdl2h and soapcpp2 tools:
#import "file.h"
instead of #include
to import other header files in a gSOAP header file for soapcpp2. The #include
and #define
directives are accepted, but are moved to the very start of the generated code for the C/C++ compiler to include before all generated definitions. You should use #include
in combinatio with "volatile" types and to ensure transient (incomplete) types are declared when these are used in the gSOAP header file.-0
.-qname
. Or add a namespace name { ... }
to the header file, but the { ... }
MUST cover the entire header file content from begin to end.-d
for DOM support and compile and link with dom.c
or dom.cpp
.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, we can copy-paste the content into our 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.
Select the project files below to peruse the source code examples.
address.xsd
Address book schemaaddress.cpp
Address book app (reads/writes address.xml file)addresstypemap.dat
Schema namespace prefix name preference for wsdl2hgraph.h
Graph data binding (tree, digraph, cyclic graph)graph.cpp
Test graph serialization as tree, digraph, and cyclicaddress.h
gSOAP-specific data binding definitions from address.xsdaddressStub.h
C++ data binding definitionsaddressH.h
SerializersaddressC.cpp
Serializersaddress.xml
Address book data generated by address appgraphStub.h
C++ data binding definitionsgraphH.h
SerializersgraphC.cpp
Serializersg.xsd
XSD schema with g:Graph
complexTypeg.nsmap
xmlns bindings namespace mapping tableBuilding 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.
To execute the AddressBook example:
./address
To execute the Graph serialization example:
./graph