LibXML(3) User Contributed Perl Documentation LibXML(3)NAMEXML::LibXML - Perl Binding for libxml2
SYNOPSIS
use XML::LibXML;
my $parser = XML::LibXML->new();
my $doc = $parser->parse_string(<<'EOT');
<some-xml/>
EOT
$Version_String = XML::LibXML::LIBXML_DOTTED_VERSION;
$Version_ID = XML::LibXML::LIBXML_VERSION;
$DLL_Version = XML::LibXML::LIBXML_RUNTIME_VERSION;
$libxmlnode = XML::LibXML->import_GDOME( $node, $deep );
$gdomenode = XML::LibXML->export_GDOME( $node, $deep );
DESCRIPTION
This module is an interface to libxml2, providing XML and HTML parsers
with DOM, SAX and XMLReader interfaces, a large subset of DOM Layer 3
interface and a XML::XPath-like interface to XPath API of libxml2. The
module is split into several packages which are not described in this
section; unless stated otherwise, you only need to "use XML::LibXML;"
in your programs.
For further information, please check the following documentation:
Parsing XML Files with XML::LibXML
XML::LibXML DOM Implementation
XML::LibXML direct SAX parser
Reading XML with a pull-parser
XML::LibXML DOM Document Class
Abstract Base Class of XML::LibXML Nodes
XML::LibXML Class for Element Nodes
XML::LibXML Class for Text Nodes
XML::LibXML Comment Nodes
XML::LibXML Class for CDATA Sections
XML::LibXML Attribute Class
XML::LibXML's DOM L2 Document Fragment Implementation
XML::LibXML Namespace Implementation
XML::LibXML Processing Instructions
XML::LibXML DTD Support
XML::LibXML frontend for RelaxNG schema validation
XML::LibXML frontend for W3C Schema schema validation
API for evaluating XPath expressions with enhanced support for the
evaluation context
ENCODINGS SUPPORT IN XML::LIBXML
Recall that since version 5.6.1, Perl distinguishes between character
strings (internally encoded in UTF-8) and so called binary data and,
accordingly, applies either character or byte semantics to them. A
scalar representing a character string is distinguished from a byte
string by special flag (UTF8). Please refer to perlunicode for
details.
XML::LibXML's API is designed to deal with many encodings of XML
documents completely transparently, so that the application using
XML::LibXML can be completely ignorant about the encoding of the XML
documents it works with. On the other hand, functions like
"XML::LibXML::Document->setEncoding" give the user control over the
document encoding.
To ensure the aforementioned transparency and uniformity, most
functions of XML::LibXML that work with in-memory trees accept and
return data as character strings (i.e. UTF-8 encoded with the UTF8 flag
on) regardless of the original document encoding; however, the
functions related to I/O operations (i.e. parsing and saving) operate
with binary data (in the original document encoding) obeying the
encoding declaration of the XML documents.
Below we summarize basic rules and principles regarding encoding:
1. Do NOT apply any encoding-related PerlIO layers (":utf8" or
":encoding(...)") to file handles that are an imput for the parses
or an ouptut for a serializer of (full) XML documents. This is
because the conversion of the data to/from the internal character
representation is provided by libxml2 itself which must be able to
enforce the encoding specified by the "<?xml version="1.0"
encoding="..."?>" declaration. Here is an example to follow:
use XML::LibXML;
my $parser = XML::LibXML->new;
open my $fh, "file.xml";
binmode $fh; # drop all PerlIO layers possibly created by a use open pragma
$doc = $parser->parse_fh($fh);
open my $out, "out.xml";
binmode $fh; # as above
$doc->toFh($fh);
# or
print $fh $doc->toString();
2. All functions working with DOM accept and return character strings
(UTF-8 encoded with UTF8 flag on). E.g.
my $doc = XML::LibXML:Document->new('1.0',$some_encoding);
my $element = $doc->createElement($name);
$element->appendText($text);
$xml_fragment = $element->toString(); # returns a character string
$xml_document = $doc->toString(); # returns a byte string
where $some_encoding is the document encoding that will be used
when saving the document, and $name and $text contain character
strings (UTF-8 encoded with UTF8 flag on). Note that the method
"toString" returns XML as a character string if applied to other
node than the Document node and a byte string containing the
apropriate
<?xml version="1.0" encoding="..."?>
declaration if appliled to a XML::LibXML DOM Document Class.
3. DOM methods also accept binary strings in the original encoding of
the document to which the node belongs (UTF-8 is assumed if the
node is not attached to any document). Exploiting this feature is
NOT RECOMMENDED since it is considered a bad practice.
my $doc = XML::LibXML:Document->new('1.0','iso-8859-2');
my $text = $doc->createTextNode($some_latin2_encoded_byte_string);
# WORKS, BUT NOT RECOMMENDED!
NOTE: libxml2 support for many encodings is based on the iconv library.
The actual list of supported encodings may vary from platform to
platform. To test if your platform works correctly with your language
encoding, build a simple document in the particular encoding and try to
parse it with XML::LibXML to see if the parser produces any errors.
Occasional crashes were reported on rare platforms that ship with a
broken version of iconv.
VERSION INFORMATION
Sometimes it is useful to figure out, for which version XML::LibXML was
compiled for. In most cases this is for debugging or to check if a
given installation meets all functionality for the package. The
functions XML::LibXML::LIBXML_DOTTED_VERSION and
XML::LibXML::LIBXML_VERSION provide this version information. Both
functions simply pass through the values of the similar named macros of
libxml2. Similarly, XML::LibXML::LIBXML_RUNTIME_VERSION returns the
version of the (usually dynamically) linked libxml2.
XML::LibXML::LIBXML_DOTTED_VERSION
$Version_String = XML::LibXML::LIBXML_DOTTED_VERSION;
Returns the version string of the libxml2 version XML::LibXML was
compiled for. This will be "2.6.2" for "libxml2 2.6.2".
XML::LibXML::LIBXML_VERSION
$Version_ID = XML::LibXML::LIBXML_VERSION;
Returns the version id of the libxml2 version XML::LibXML was
compiled for. This will be "20602" for "libxml2 2.6.2". Don't mix
this version id with $XML::LibXML::VERSION. The latter contains the
version of XML::LibXML itself while the first contains the version
of libxml2 XML::LibXML was compiled for.
XML::LibXML::LIBXML_RUNTIME_VERSION
$DLL_Version = XML::LibXML::LIBXML_RUNTIME_VERSION;
Returns a version string of the libxml2 which is (usually
dynamically) linked by XML::LibXML. This will be "20602" for
libxml2 released as "2.6.2" and something like "20602-CVS2032" for
a CVS build of libxml2.
XML::LibXML issues a warning if the version of libxml2 dynamically
linked to it is less than the version of libxml2 which it was
compiled against.
EXPORTS
By default the module exports all constants and functions listed in the
:all tag, described below.
EXPORT TAGS
:all
Includes the tags ":libxml", ":encoding", and ":ns" described
below.
:libxml
Exports integer constants for DOM node types (defined in a
separately distributed XML::LibXML::Common module).
XML_ELEMENT_NODE => 1
XML_ATTRIBUTE_NODE => 2
XML_TEXT_NODE => 3
XML_CDATA_SECTION_NODE => 4
XML_ENTITY_REF_NODE => 5
XML_ENTITY_NODE => 6
XML_PI_NODE => 7
XML_COMMENT_NODE => 8
XML_DOCUMENT_NODE => 9
XML_DOCUMENT_TYPE_NODE => 10
XML_DOCUMENT_FRAG_NODE => 11
XML_NOTATION_NODE => 12
XML_HTML_DOCUMENT_NODE => 13
XML_DTD_NODE => 14
XML_ELEMENT_DECL => 15
XML_ATTRIBUTE_DECL => 16
XML_ENTITY_DECL => 17
XML_NAMESPACE_DECL => 18
XML_XINCLUDE_START => 19
XML_XINCLUDE_END => 20
:encoding
Exports two encoding conversion functions from the (separate)
module XML::LibXML::Common.
encodeToUTF8()decodeFromUTF8()
:libxml
Exports two convenience constants: the implicit namespace of the
reserved "xml:" prefix, and the implicit namespace for the reserved
"xmlns:" prefix.
XML_XML_NS => 'http://www.w3.org/XML/1998/namespace'
XML_XMLNS_NS => 'http://www.w3.org/2000/xmlns/'
RELATED MODULES
The modules described in this section are not part of the XML::LibXML
package itself. As they support some additional features, they are
mentioned here.
XML::LibXSLT
XSLT 1.0 Processor using libxslt and XML::LibXML
XML::LibXML::Common
Common functions for XML::LibXML related Classes
XML::LibXML::Iterator
XML::LibXML Implementation of the DOM Traversal Specification
XML::LIBXML AND XML::GDOME
Note: THE FUNCTIONS DESCRIBED HERE ARE STILL EXPERIMENTAL
Although both modules make use of libxml2's XML capabilities, the DOM
implementation of both modules are not compatible. But still it is
possible to exchange nodes from one DOM to the other. The concept of
this exchange is pretty similar to the function cloneNode(): The
particular node is copied on the low-level to the opposite DOM
implementation.
Since the DOM implementations cannot coexist within one document, one
is forced to copy each node that should be used. Because you are always
keeping two nodes this may cause quite an impact on a machines memory
usage.
XML::LibXML provides two functions to export or import GDOME nodes:
import_GDOME() and export_GDOME(). Both function have two parameters:
the node and a flag for recursive import. The flag works as in
cloneNode().
The two functions allow to export and import XML::GDOME nodes
explicitly, however, XML::LibXML allows also the transparent import of
XML::GDOME nodes in functions such as appendChild(), insertAfter() and
so on. While native nodes are automatically adopted in most functions
XML::GDOME nodes are always cloned in advance. Thus if the original
node is modified after the operation, the node in the XML::LibXML
document will not have this information.
import_GDOME
$libxmlnode = XML::LibXML->import_GDOME( $node, $deep );
This clones an XML::GDOME node to a XML::LibXML node explicitly.
export_GDOME
$gdomenode = XML::LibXML->export_GDOME( $node, $deep );
Allows to clone an XML::LibXML node into a XML::GDOME node.
CONTACTS
For bug reports, please use the CPAN request tracker on
http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-LibXML
For suggestions etc., and other issues related to XML::LibXML you may
use the perl XML mailing list ("perl-xml@listserv.ActiveState.com"),
where most XML-related Perl modules are discussed. In case of problems
you should check the archives of that list first. Many problems are
already discussed there. You can find the list's archives and
subscription options at
<http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml|http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml>.
AUTHORS
Matt Sergeant, Christian Glahn, Petr Pajas
VERSION
1.66
COPYRIGHT
2001-2007, AxKit.com Ltd; 2002-2006 Christian Glahn; 2006-2008 Petr
Pajas, All rights reserved.
perl v5.10.0 2008-01-29 LibXML(3)
