Provided by: libsoap-lite-perl_1.09-1_all 
NAME
SOAP::Serializer - the means by which the toolkit manages the expression of data as XML
DESCRIPTION
The SOAP::Serializer class is the means by which the toolkit manages the expression of
data as XML. The object that a SOAP::Lite instance uses by default is generally enough for
the task, with no need for the application to create its own. The main purpose of this
class is to provide a place for applications to extend the serializer by defining
additional methods for handling new datatypes.
METHODS
new(optional key/value pairs)
$serialize = SOAP::Serializer->new( );
This is the constructor method for the class. In addition to creating a basic object
and initializing it with default values, the constructor can also take names and
values for most of the accessor methods that the class supports.
envelope(method, data arguments)
$serialize->envelope(fault => $fault_obj);
Provides the core purpose for the SOAP::Serializer class. It creates the full SOAP
envelope based on the input passed in to it. The data arguments passed in the list of
parameters to the method are divided into two sublists: any parameters that are
SOAP::Header objects or derivatives of go into one list, while the remainder go into
the other. The nonheader objects are used as the content for the message body, with
the body itself being largely dependent on the value of the first argument in the
list. This argument is expected to be a string and should be one of the following:
context
$serialize->context->packager();
This provides access to the calling context of "SOAP::Serializer". In a client side
context the often means a reference to an instance of SOAP::Lite. In a server side
context this means a reference to a SOAP::Server instance.
method
The envelope is being created to encapsulate a RPC-style method call.
response
The message being created is that of a response stemming from a RPC-style method
call.
fault
For this specifier, the envelope being created is to transmit a fault.
freeform
This identifier is used as a general-case encoding style for messages that don't
fit into any of the previous cases. The arguments are encoded into the envelope's
Body tag without any sort of context sensitivity.
Any value other than these four results in an error.
envprefix(optional value)
$serialize->envprefix('env');
Gets or sets the prefix that labels the SOAP envelope namespace. This defaults to
SOAP-ENV.
encprefix(optional value)
$serialize->envprefix('enc');
Gets or sets the prefix that labels the SOAP encoding namespace. Defaults to SOAP-ENC.
soapversion(optional value)
$serialize->soapversion('1.2');
If no parameter is given, returns the current version of SOAP that is being used as
the basis for serializing messages. If a parameter is given, attempts to set that as
the version of SOAP being used. The value should be either 1.1 or 1.2. When the SOAP
version is being set, the package selects new URNs for envelope and encoding spaces
and also calls the xmlschema method to set the appropriate schema definition.
xmlschema(optional value)
$serialize->xmlschema($xml_schema_1999);
Gets or sets the URN for the schema being used to express the structure of the XML
generated by the serializer. If setting the value, the input must be the full URN for
the new schema and is checked against the list of known SOAP schemas.
register_ns
The register_ns subroutine allows users to register a global namespace with the SOAP
Envelope. The first parameter is the namespace, the second parameter to this
subroutine is an optional prefix. If a prefix is not provided, one will be generated
automatically for you. All namespaces registered with the serializer get declared in
the <soap:Envelope /> element.
find_prefix
The find_prefix subroutine takes a namespace as a parameter and returns the assigned
prefix to that namespace. This eliminates the need to declare and redeclare namespaces
within an envelope. This subroutine is especially helpful in determining the proper
prefix when assigning a type to a SOAP::Data element. A good example of how this might
be used is as follows:
SOAP::Data->name("foo" => $inputParams{'foo'})
->type($client->serializer->find_prefix('urn:Foo').':Foo');
CUSTOM DATA TYPES
When serializing an object, or blessed hash reference, into XML, "SOAP::Serializer" first
checks to see if a subroutine has been defined for the corresponding class name. For
example, in the code below, "SOAP::Serializer" will check to see if a subroutine called
"as_MyModule__MyPackage" has been defined. If so, then it will pass $foo to that
subroutine along with other data known about the "SOAP::Data" element being encoded.
$foo = MyModule::MyPackage->new;
my $client = SOAP::Lite
->uri($NS)
->proxy($HOST);
$som = $client->someMethod(SOAP::Data->name("foo" => $foo));
as_TypeName SUBROUTINE REQUIREMENTS
Naming Convention
The subroutine should always be prepended with "as_" followed by the type's name. The
type's name must have all colons (':') substituted with an underscore ('_').
Input
The input to "as_TypeName" will have at least one parameter, and at most four
parameters. The first parameter will always be the value or the object to be encoded.
The following three parameters depend upon the context of the value/object being
encoded.
If the value/object being encoded was part of a "SOAP::Data" object (as in the above
example), then the second, third and fourth parameter will be the "SOAP::Data"
element's name, type, and attribute set respectively. If on the other hand, the
value/object being encoded is not part of a "SOAP::Data" object, as in the code below:
$foo = MyModule::MyPackage->new;
my $client = SOAP::Lite
->uri($NS)
->proxy($HOST);
$som = $client->someMethod($foo);
Then the second and third parameters will be the class name of the value/object being
encoded (e.g. "MyModule::MyPackage" in the example above), and the fourth parameter
will be an empty hash.
Output
The encoding subroutine must return an array containing three elements: 1) the name of
the XML element, 2) a hash containing the attributes to be placed into the element,
and 3) the value of the element.
AUTOTYPING
When the type of an element has not been declared explicitly, SOAP::Lite must "guess" at
the object's type. That is due to the fact that the only form of introspection that Perl
provides (through the use of the "ref" subroutine) does not provide enough information to
"SOAP::Serializer" to allow SOAP::Lite to determine the exact type of an element being
serialized.
To work around this limitation, the "SOAP::Serializer::typelookup" hash was created. This
hash is populated with all the data types that the current "SOAP::Serializer" can auto
detect. Users and developers are free to modify the contents of this hash allowing them to
register new data types with the system.
When "SOAP::Serializer" is asked to encode an object into XML, it goes through the
following steps. First, "SOAP::Serializer" checks to see if a type has been explicitly
stated for the current object. If a type has been provided "SOAP::Serializer" checks to
see if an "as_TypeName" subroutine as been defined for that type. If such a subroutine
exists, then "SOAP::Serializer" passes the object to it to be encoded. If the subroutine
does not exist, or the type has not been provided, then "SOAP::Serializer" must attempt to
"guess" the type of the object being serialized.
To do so, "SOAP::Serializer" runs in sequence a set of tests stored in the
"SOAP::Serializer::typelookup" hash. "SOAP::Serializer" continues to run each test until
one of the tests returns true, indicating that the type of the object has been detected.
When the type of the object has been detected, then "SOAP::Serializer" passes the object
to the encoding subroutine that corresponds with the test that was passed. If all the
tests fail, and the type was not determined, then "SOAP::Serializer" will as a last resort
encode the object based on one of the four basic data types known to Perl: REF, SCALAR,
ARRAY and HASH.
The following table contains the set of data types detectable by "SOAP::Lite" by default
and the order in which their corresponding test subroutine will be run, according to their
precedence value.
Table 1 - Autotyping Precedence
TYPENAME PRECEDENCE VALUE
----------------------------
base64 10
int 20
long 25
float 30
gMonth 35
gDay 40
gYear 45
gMonthDay 50
gYearMonth 55
date 60
time 70
dateTime 75
duration 80
boolean 90
anyURI 95
string 100
REGISTERING A NEW DATA TYPE
To register a new data type that can be automatically detected by "SOAP::Lite" and then
serialized into XML, the developer must provide the following four things:
• The name of the new data type.
• A subroutine that is capable of detecting whether a value passed to it is of the
corresponding data type.
• A number representing the test subroutine's precedence relative to all the other
types' test subroutinestypes. See Table 1 - Autotyping Precedence.
• A subroutine that is capable of providing "SOAP::Serializer" with the information
necessary to serialize an object of the corresponding data type into XML.
EXAMPLE 1
If, for example, you wish to create a new datatype called "uriReference" for which you
would like Perl values to be automatically detected and serialized into, then you follow
these steps.
Step 1: Write a Test Subroutine
The test subroutine will have passed to it by "SOAP::Serializer" a value to be tested. The
test subroutine must return 1 if the value passed to it is of the corresponding type, or
else it must return 0.
sub SOAP::Serializer::uriReferenceTest {
my ($value) = @_;
return 1 if ($value =~ m!^http://!);
return 0;
}
Step 2: Write an Encoding Subroutine
The encoding subroutine provides "SOAP::Serializer" with the data necessary to encode the
value passed to it into XML. The encoding subroutine name's should be of the following
format: "as_"<Type Name>.
The encoding subroutine will have passed to it by "SOAP::Serializer" four parameters: the
value to be encoded, the name of the element being encoded, the assumed type of the
element being encoded, and a reference to a hash containing the attributes of the element
being encoded. The encoding subroutine must return an array representing the encoded
datatype. "SOAP::Serializer" will use the contents of this array to generate the
corresponding XML of the value being encoded, or serialized. This array contains the
following 3 elements: the name of the XML element, a hash containing the attributes to be
placed into the element, and the value of the element.
sub SOAP::Serializer::as_uriReference {
my $self = shift;
my($value, $name, $type, $attr) = @_;
return [$name, {'xsi:type' => 'xsd:uriReference', %$attr}, $value];
}
Step 3: Register the New Data Type
To register the new data type, simply add the type to the "SOAP::Serializer::typelookup"
hash using the type name as the key, and an array containing the precedence value, the
test subroutine, and the encoding subroutine.
$s->typelookup->{uriReference}
= [11, \&uriReferenceTest, 'as_uriReference'];
Tip: As a short hand, you could just as easily use an anonymous test subroutine when
registering the new datatype in place of the "urlReferenceTest" subroutine above. For
example:
$s->typelookup->{uriReference}
= [11, sub { $_[0] =~ m!^http://! }, 'as_uriReference'];
Once complete, "SOAP::Serializer" will be able to serialize the following "SOAP::Data"
object into XML:
$elem = SOAP::Data->name("someUri" => 'http://yahoo.com')->type('uriReference');
"SOAP::Serializer" will also be able to automatically determine and serialize the
following untyped "SOAP::Data" object into XML:
$elem = SOAP::Data->name("someUri" => 'http://yahoo.com');
ACKNOWLEDGEMENTS
Special thanks to O'Reilly publishing which has graciously allowed SOAP::Lite to republish
and redistribute large excerpts from Programming Web Services with Perl, mainly the
SOAP::Lite reference found in Appendix B.
COPYRIGHT
Copyright (C) 2000-2004 Paul Kulchenko. All rights reserved.
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
AUTHORS
Paul Kulchenko (paulclinger@yahoo.com)
Randy J. Ray (rjray@blackperl.com)
Byrne Reese (byrne@majordojo.com)