Provided by: libxml-compile-perl_1.63-3_all 
NAME
XML::Compile::Translate::Reader - translate XML to HASH
INHERITANCE
XML::Compile::Translate::Reader
is a XML::Compile::Translate
SYNOPSIS
my $schema = XML::Compile::Schema->new(...);
my $code = $schema->compile(READER => ...);
DESCRIPTION
The translator understands schemas, but does not encode that into actions. This module
implements those actions to translate from XML into a (nested) Perl HASH structure.
Extends "DESCRIPTION" in XML::Compile::Translate.
METHODS
Extends "METHODS" in XML::Compile::Translate.
DETAILS
Extends "DETAILS" in XML::Compile::Translate.
Translator options
Extends "Translator options" in XML::Compile::Translate.
Processing Wildcards
If you want to collect information from the XML structure, which is permitted by "any" and
"anyAttribute" specifications in the schema, you have to implement that yourself. The
problem is "XML::Compile" has less knowledge than you about the possible data.
option any_attribute
By default, the "anyAttribute" specification is ignored. When "TAKE_ALL" is given, all
attributes which are fulfilling the name-space requirement added to the returned data-
structure. As key, the absolute element name will be used, with as value the related
unparsed XML element.
In the current implementation, if an explicit attribute is also covered by the name-spaces
permitted by the anyAttribute definition, then it will also appear in that list (and hence
the handler will be called as well).
Use XML::Compile::Schema::compile(any_attribute) to write your own handler, to influence
the behavior. The handler will be called for each attribute, and you must return list of
pairs of derived information. When the returned is empty, the attribute data is lost.
The value may be a complex structure.
option any_element
By default, the "any" definition in a schema will ignore all elements from the container
which are not used. Also in this case "TAKE_ALL" is required to produce "any" results.
"SKIP_ALL" will ignore all results, although this are being processed for validation
needs.
option any_type CODE
By default, the elements which have type "xsd:anyType" will return an XML::LibXML::Element
when there are sub-elements. Otherwise, it will return the textual content.
If you pass your own CODE reference, you can change this behavior. It will get called
with the path, the node, and the default handler. Be awayre the $node may actually be a
string already.
$schema->compile(READER => ..., any_type => \&handle_any_type);
sub handle_any_type($$$)
{ my ($path, $node, $handler) = @_;
ref $node or return $node;
$node;
}
Mixed elements
[available since 0.86] ComplexType and ComplexContent components can be declared with the
"<mixed="true""> attribute. This implies that text is not limited to the content of
containers, but may also be used inbetween elements. Usually, you will only find
ignorable white-space between elements.
In this example, the "a" container is marked to be mixed:
<a id="5"> before <b>2</b> after </a>
Often the "mixed" option is bending one of both ways: either the element is needed as
text, or the element should be parsed and the text ignored. The reader has various
options to avoid the need of processing raw XML::LibXML nodes.
[1.00] When the return is a HASH, that HASH will also contain the "_MIXED_ELEMENT_MODE"
key, to help people understand what happens. This is not possible for all modes, only for
some.
With XML::Compile::Schema::compile(mixed_elements) set to
ATTRIBUTES (the default)
a HASH is returned, the attributes are processed. The node is found as
XML::LibXML::Element with the key '_'. Above example will produce
$r = { id => 5, _ => $xmlnode };
TEXTUAL
Like the previous, but now the textual representation of the content is returned with
key '_'. Above example will produce
$r = { id => 5, _ => ' before 2 after '};
STRUCTURAL
will remove all mixed-in text, and treat the element as normal element. The example
will be transformed into
$r = { id => 5, b => 2 };
XML_NODE
return the XML::LibXML::Node itself. The example:
$r = $xmlnode;
XML_STRING
return the mixed node as XML string, just as in the source. Be warned that it is
rather expensive: the string was parsed and then stringified again, which is costly
for large nodes. Result:
$r = '<a id="5"> before <b>2</b> after </a>';
CODE reference
the reference is called with the XML::LibXML::Node as first argument. When a value is
returned (even undef), then the right tag with the value will be included in the
translators result. When an empty list is returned by the code reference, then
nothing is returned (which may result in an error if the element is required according
to the schema)
When some of your mixed elements need different behavior from other elements, then you
have to go play with the normal hooks in specific cases.
Schema hooks
hooks executed before the XML is being processed
The "before" hooks receives an XML::LibXML::Node object and the path string. It must
return a new (or same) XML node which will be used from then on. You probably can best
modify a node clone, not the original as provided by the user. When "undef" is returned,
the whole node will disappear.
This hook offers a predefined "PRINT_PATH".
hooks executed as replacement
Your "replace" hook should return a list of key-value pairs. To produce it, it will get
the XML::LibXML::Element, the translator settings as HASH, the path, and the localname.
This hook has a predefined "SKIP", which will not process the found element, but simply
return the string "SKIPPED" as value. This way, a whole tree of unneeded translations can
be avoided.
[1.51] The predefined hook "XML_NODE" will not attempt to parse the selected element, but
returns the XML::LibXML::Element node instead. This may break on some schema-contained
validations.
Sometimes, the Schema spec is such a mess, that XML::Compile cannot automatically
translate it. I have seen cases where confusion over name-spaces is created: a choice
between three elements with the same name but different types. Well, in such case you may
use XML::LibXML::Simple to translate a part of your tree. Simply
use XML::LibXML::Simple qw/XMLin/;
$schema->addHook
( action => 'READER'
, type => 'tns:xyz' # or pack_type($tns,'xyz')
# path => qr!/company$! # by element name
, replace =>
sub { my ($xml, $args, $path, $type, $r) = @_;
($type => XMLin($xml, ...));
}
);
hooks for post-processing, after the data is collected
Your code reference gets called with three parameters: the XML node, the data collected
and the path. Be careful that the collected data might be a SCALAR (for simpleType).
Return a HASH or a SCALAR. "undef" may work, unless it is the value of a required element
you throw awy.
This hook also offers a predefined "PRINT_PATH". Besides, it has "INCLUDE_PATH",
"XML_NODE", "NODE_TYPE", "ELEMENT_ORDER", and "ATTRIBUTE_ORDER", which will result in
additional fields in the HASH, respectively containing the NODE which was processed (an
XML::LibXML::Element), the type_of_node, the element names, and the attribute names. The
keys start with an underscore "_".
Typemaps
In a typemap, a relation between an XML element type and a Perl class (or object) is made.
Each translator back-end will implement this a little differently. This section is about
how the reader handles typemaps.
Typemap to Class
Usually, an XML type will be mapped on a Perl class. The Perl class implements the
"fromXML" method as constructor.
$schema->addTypemaps($sometype => 'My::Perl::Class');
package My::Perl::Class;
...
sub fromXML
{ my ($class, $data, $xmltype) = @_;
my $self = $class->new($data);
...
$self;
}
Your method returns the data which will be included in the result tree of the reader. You
may return an object, the unmodified $data, or "undef". When "undef" is returned, this
may fail the schema parser when the data element is required.
In the simpelest implementation, the class stores its data exactly as the XML structure:
package My::Perl::Class;
sub fromXML
{ my ($class, $data, $xmltype) = @_;
bless $data, $class;
}
# The same, even shorter:
sub fromXML { bless $_[1], $_[0] }
Typemap to Object
Another option is to implement an object factory: one object which creates other objects.
In this case, the $xmltype parameter can come of use, to have one object spawning many
different other objects.
my $object = My::Perl::Class->new(...);
$schema->typemap($sometype => $object);
package My::Perl::Class;
sub fromXML
{ my ($object, $xmltype, $data) = @_;
return Some::Other::Class->new($data);
}
This object factory may be a very simple solution when you map XML onto objects which are
not under your control; where there is not way to add the "fromXML" method.
Typemap to CODE
The light version of an object factory works with CODE references.
$schema->typemap($t1 => \&myhandler);
sub myhandler
{ my ($backend, $data, $type) = @_;
return My::Perl::Class->new($data)
if $backend eq 'READER';
$data;
}
# shorter
$schema->typemap($t1 => sub {My::Perl::Class->new($_[1])} );
Typemap implementation
Internally, the typemap is simply translated into an "after" hook for the specific type.
After the data was processed via the usual mechanism, the hook will call method "fromXML"
on the class or object you specified with the data which was read. You may still use
"before" and "replace" hooks, if you need them.
Syntactic sugar:
$schema->typemap($t1 => 'My::Package');
$schema->typemap($t2 => $object);
is comparible to
$schema->typemap($t1 => sub {My::Package->fromXML(@_)});
$schema->typemap($t2 => sub {$object->fromXML(@_)} );
with some extra checks.
SEE ALSO
This module is part of XML-Compile distribution version 1.63, built on July 02, 2019.
Website: http://perl.overmeer.net/xml-compile/
LICENSE
Copyrights 2006-2019 by [Mark Overmeer <markov@cpan.org>]. For other contributors see
ChangeLog.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself. See http://dev.perl.org/licenses/