=pod

=head1 NAME

SOAP::WSDL::Manual::Parser - How SOAP::WSDL parses XML messages

=head1 Which XML message does SOAP::WSDL parse ?

Naturally, there are two kinds of XML documents (or messages) SOAP::WSDL has
to parse:

=over

=item * WSDL definitions

=item * SOAP messages

=back

There are different parser implementations available for SOAP messages and
WSDL definitions.

=head1 WSDL definitions parser

=head2 SOAP::WSDL::Expat::WSDLParser

A parser for WSDL definitions based on L<XML::Parser::Expat|XML::Parser::Expat>.

 my $parser = SOAP::WSDL::Expat::WSDLParser->new();
 my $wsdl = $parser->parse_file( $filename );

The WSDL parser creates a tree of perl objects, whose root is a
L<SOAP::WSDL::Definitions|SOAP::WSDL::Definitions> element.

=head1 SOAP messages parser

=head2 SOAP::WSDL::Expat::MessageParser

L<SOAP::WSDL::Expat::MessageParser|SOAP::WSDL::Expat::MessageParser> converts
SOAP messages to SOAP::WSDL::XSD object trees.

It uses a class resolvers for finding out which class
a particular XML element should be of, and type libs containing these classes.

=head3 Creating a class resolver

The easiest way for creating a class resolver is to run SOAP::WSDL's generator.

See L<wsdl2perl.pl>.

The class resolver must implement a class method "get_class", which is passed
a list ref of the current element's XPath (relative to Body), split by /.

This method must return a class name appropriate for a XML element.

A class resolver package might look like this:

 package ClassResolver;

 my %class_list = (
    'EnqueueMessage' => 'Typelib::TEnqueueMessage',
    'EnqueueMessage/MMessage' => 'Typelib::TMessage',
    'EnqueueMessage/MMessage/MRecipientURI' => 'SOAP::WSDL::XSD::Builtin::anyURI',
    'EnqueueMessage/MMessage/MMessageContent' => 'SOAP::WSDL::XSD::Builtin::string',
 );

 sub new { return bless {}, 'ClassResolver' };

 sub get_class {
    my $name = join('/', @{ $_[1] });
    return ($class_list{ $name }) ? $class_list{ $name }
        : warn "no class found for $name";
 };
 1;

=head3 Skipping unwanted items

Sometimes there's unnecessary information transported in SOAP messages.

To skip XML nodes (including all child nodes), just edit the type map for
the message and set the type map entry to '__SKIP__'.

In the example above, EnqueueMessage/StuffIDontNeed and all child elements
are skipped.

 my %class_list = (
    'EnqueueMessage' => 'Typelib::TEnqueueMessage',
    'EnqueueMessage/MMessage' => 'Typelib::TMessage',
    'EnqueueMessage/MMessage/MRecipientURI' => 'SOAP::WSDL::XSD::Builtin::anyURI',
    'EnqueueMessage/MMessage/MMessageContent' => 'SOAP::WSDL::XSD::Builtin::string',
    'EnqueueMessage/StuffIDontNeed' => '__SKIP__',
    'EnqueueMessage/StuffIDontNeed/Foo' => 'SOAP::WSDL::XSD::Builtin::string',
    'EnqueueMessage/StuffIDontNeed/Bar' => 'SOAP::WSDL::XSD::Builtin::string',
 );

Note that only SOAP::WSDL::Expat::MessageParser implements skipping elements
at the time of writing.

=head3 Creating type lib classes

Every element must have a correspondent one in the type library.

Builtin types should be resolved as SOAP::WSDL::XSD::Builtin::* classes

Creating a type lib is easy: Just run SOAP::WSDL's generator - it will
create both a typemap and the type lib classes for a WSDL file.

Sometimes it is nessecary to create type lib classes by hand - not all
WSDL definitions are complete.

For writing your own lib classes, see L<SOAP::WSDL::XSD::Typelib::Element>,
L<SOAP::WSDL::XSD::Typelib::ComplexType> and L<SOAP::WSDL::XSD::Typelib::SimpleType>.

=head2 SOAP::WSDL::Expat::Message2Hash

Transforms a SOAP message into a perl hash refs. Using this parser is usually
triggered by calling the C<outputhash> method of SOAP::WSDL, or by using
L<SOAP::WSDL::Deserializer::Hash|SOAP::WSDL::Deserializer::Hash>.

Acts somewhat like XML::Simple, but faster.

The following restrictions apply:

=over

=item * Ignores all namespaces

=item * Ignores all attributes

=item * Does not handle mixed content

=item * The SOAP header is ignored

=back

=cut

=head1 OLD SAX HANDLER

Historically, SOAP::WSDL used SAX for parsing XML. The SAX handlers were
implemented as L<XML::LibXML|XML::LibXML> handlers, which also worked with
L<XML::SAX::ParserFactory|XML::SAX::ParserFactory>.

Support for SAX and L<XML::LibXML|XML::LibXML> in SOAP::WSDL is discontinued
for the following reasons:

=over

=item * Speed

L<XML::Parser::Expat|XML::Parser::Expat> is faster than
L<XML::LibXML|XML::LibXML> - at least when optimized for speed.

High parsing speed is one of the key requirements for a SOAP toolkit - if XML
serializing and (more important) deserializing are not fast enough, the whole
toolkit is unusable.

=item * Availability

L<XML::Parser|XML::Parser> is more popular than L<XML::LibXML|XML::LibXML>.

=item * Stability

XML::LibXML is based on the libxml2 library. Several versions of
libxml2 are known to have specific bugs. As a workaround, there are
often several versions of libxml2 installed on one system. This may
lead to problems on operating systems which cannot load more than
one version of a shared library simultaneously.

XML::LibXML is also still under development, while XML::Parser has had time
to stabilize.

=item * SOAP::Lite uses XML::Parser

L<SOAP::Lite|SOAP::Lite> uses L<XML::Parser|XML::Parser> if available.
SOAP::WSDL should not require users to install both L<XML::Parser|XML::Parser>
and L<XML::LibXML|XML::LibXML>.

=back

The old SAX handler historically used in SOAP::WSDL are not included in
the SOAP::WSDL package any more.

However, they may be obtained from the "attic" directory in
SOAP::WSDL's SVN repository at

https://soap-wsdl.svn.sourceforge.net/svnroot/soap-wsdl/SOAP-WSDL/trunk/attic

=over

=item * SOAP::WSDL::SAX::WSDLHandler

This is a SAX handler for parsing WSDL files into object trees SOAP::WSDL
works with.

It's built as a native handler for XML::LibXML, but will also work with
XML::SAX::ParserFactory.

To parse a WSDL file, use one of the following variants:

 my $parser = XML::LibXML->new();
 my $handler = SOAP::WSDL::SAX::WSDLHandler->new();
 $parser->set_handler( $handler );
 $parser->parse( $xml );
 my $data = $handler->get_data();
 
 my $handler = SOAP::WSDL::SAX::WSDLHandler->new({
        base => 'XML::SAX::Base'
 });
 my $parser = XML::SAX::ParserFactor->parser(
    Handler => $handler
 );
 $parser->parse( $xml );
 my $data = $handler->get_data();

=item * SOAP::WSDL::SAX::MessageHandler

This is a SAX handler for parsing WSDL files into object trees SOAP::WSDL
works with.

It's built as a native handler for XML::LibXML, but will also work with
XML::SAX::ParserFactory.

Can be used for parsing both streams (chunks) and documents.

=back

=head1 LICENSE AND COPYRIGHT

Copyright 2007 Martin Kutter.

This file is part of SOAP-WSDL. You may distribute/modify it under
the same terms as perl itself.

=head1 AUTHOR

Martin Kutter E<lt>martin.kutter fen-net.deE<gt>

=head1 REPOSITORY INFORMATION

 $Rev: 391 $
 $LastChangedBy: kutterma $
 $Id: Parser.pod 391 2007-11-17 21:56:13Z kutterma $
 $HeadURL: https://soap-wsdl.svn.sourceforge.net/svnroot/soap-wsdl/SOAP-WSDL/trunk/lib/SOAP/WSDL/Manual/Parser.pod $

=cut