XML::LibXML::Document

Section: User Contributed Perl Documentation (3)
Updated: 2003-11-07
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NAME

XML::LibXML::Document - XML::LibXML DOM Document Class  

SYNOPSIS

  $dom = XML::LibXML::Document->new( $version, $encoding );
  $dom = XML::LibXML::Document->createDocument( $version, $encoding );
  $strEncoding = $doc->encoding();
  $doc->setEncoding($new_encoding);
  $strVersion = $doc->version();
  $doc->standalone
  $doc->setStandalone($numvalue);
  my $compression = $doc->compression;
  $doc->setCompression($ziplevel);
  $docstring = $dom->toString($format);
  $c14nstr = $doc->toStringC14N($comment_flag,$xpath); 
  $str = $doc->serialze($format); 
  $c14nstr = $doc->serialize_c14n($comment_flag,$xpath); 
  $state = $doc->toFile($filename, $format);
  $state = $doc->toFH($fh, $format);
  $str = $document->toStringHTML();
  $str = $document->serialize_html();
  $bool = $dom->is_valid();
  $dom->validate();
  $root = $dom->documentElement();
  $dom->setDocumentElement( $root );
  $element = $dom->createElement( $nodename );
  $element = $dom->createElementNS( $namespaceURI, $qname );
  $text = $dom->createTextNode( $content_text );
  $comment = $dom->createComment( $comment_text );
  $attrnode = $doc->createAttribute($name [,$value]);
  $attrnode = $doc->createAttributeNS( namespaceURI, $name [,$value] );
  $fragment = $doc->createDocumentFragment()
  $cdata = $dom->create( $cdata_content );
  my $pi = $doc->createProcessingInstruction( $target, $data );
  my $entref = $doc->createEntityReference($refname);
  $dtd = $document->createInternalSubset( $rootnode, $public, $system);
  $dtd = $document->createExternalSubset( $rootnode, $public, $system);
  $document->importNode( $node );
  $document->adoptNode( $node );
  my $dtd = $doc->externalSubset;
  my $dtd = $doc->internalSubset;
  $doc->setExternalSubset($dtd);
  $doc->setInternalSubset($dtd);
  my $dtd = $doc->removeExternalSubset();
  my $dtd = $doc->removeInternalSubset();
  my @nodelist = $doc->getElementsByTagName($tagname);
  my @nodelist = $doc->getElementsByTagName($nsURI,$tagname);
  my @nodelist = $doc->getElementsByLocalName($localname);
  my $node = $doc->getElementsById($id);
  $dom->indexElements();

 

DESCRIPTION

The Document Class is in most cases the result of a parsing process. But sometimes it is necessary to create a Document from scratch. The DOM Document Class provides functions that conform to the DOM Core naming style.

It inherits all functions from XML::LibXML::Node as specified in the DOM specification. This enables access to the nodes besides the root element on document level - a DTD for example. The support for these nodes is limited at the moment.

While generaly nodes are bound to a document in the DOM concept it is suggested that one should always create a node not bound to any document. There is no need of really including the node to the document, but once the node is bound to a document, it is quite safe that all strings have the correct encoding. If an unbound textnode with an iso encoded string is created (e.g. with $CLASS->new()), the toString function may not return the expected result.

All this seems like a limitation as long as UTF8 encoding is assured. If iso encoded strings come into play it is much safer to use the node creation functions of XML::LibXML::Document.

new
  $dom = XML::LibXML::Document->new( $version, $encoding );

alias for createDocument()

createDocument
  $dom = XML::LibXML::Document->createDocument( $version, $encoding );

The constructor for the document class. As Parameter it takes the version string and (optionally) the encoding string. Simply calling createDocument() will create the document:

  <?xml version="your version" encoding="your encoding"?>

Both parameter are optional. The default value for $version is 1.0, of course. If the $encoding parameter is not set, the encoding will be left unset, which means UTF8 is implied.

The call of createDocument() without any parameter will result the following code:

  <?xml version="1.0"?>

Alternatively one can call this constructor directly from the XML::LibXML class level, to avoid some typing. This will not have any effect on the class instance, which is always XML::LibXML::Document.

   my $document = XML::LibXML->createDocument( "1.0", "UTF8" );

is therefore a shortcut for

  my $document = XML::LibXML::Document->createDocument( "1.0", "UTF8" );

encoding
  $strEncoding = $doc->encoding();

returns the encoding string of the document.

  my $doc = XML::LibXML->createDocument( "1.0", "ISO-8859-15" );
  print $doc->encoding; # prints ISO-8859-15

Optionally this function can be accessed by actualEncoding or getEncoding.

setEncoding
  $doc->setEncoding($new_encoding);

From time to time it is useful to change the effective encoding of a document. This method provides the interface to manipulate the encoding of a document.

Note that this function has to be used very carefully, since you can't simply convert one encoding in any other, since some (or even all) characters may not exist in the new encoding. XML::LibXML will not test if the operation is allowed or possible for the given document. The only switching assured to work is to UTF8.

version
  $strVersion = $doc->version();

returns the version string of the document

getVersion() is an alternative form of this function.

standalone
  $doc->standalone

This function returns the Numerical value of a documents XML declarations standalone attribute. It returns 1 if standalone=``yes'' was found, 0 if standalone=``no'' was found and -1 if standalone was not specified (default on creation).

setStandalone
  $doc->setStandalone($numvalue);

Through this method it is possible to alter the value of a documents standalone attribute. Set it to 1 to set standalone=``yes'', to 0 to set standalone=``no'' or set it to -1 to remove the standalone attribute from the XML declaration.

compression
  my $compression = $doc->compression;

libxml2 allows reading of documents directly from gziped files. In this case the compression variable is set to the compression level of that file (0-8). If XML::LibXML parsed a different source or the file wasn't compressed, the returned value will be -1.

setCompression
  $doc->setCompression($ziplevel);

If one intends to write the document directly to a file, it is possible to set the compression level for a given document. This level can be in the range from 0 to 8. If XML::LibXML should not try to compress use -1 (default).

Note that this feature will only work if libxml2 is compiled with zlib support and toFile() is used for output.

toString
  $docstring = $dom->toString($format);

toString is a deparsing function, so the DOM Tree can be translated into a string, ready for output.

The optional $format parameter sets the indenting of the output. This parameter is expected to be an integer value, that specifies that indentation should be used. The format parameter can have three different values if it is used:

If $format is 0, than the document is dumped as it was originally parsed

If $format is 1, libxml2 will add ignorable whitespaces, so the nodes content is easier to read. Existing text nodes will not be altered

If $format is 2 (or higher), libxml2 will act as $format == 1 but it add a leading and a trailing linebreak to each text node.

libxml2 uses a hardcoded indentation of 2 space characters per indentation level. This value can not be altered on runtime.

NOTE: XML::LibXML::Document::toString returns the data in the document encoding rather than UTF8! If you want UTF8 ecoded XML, you have to change the conding by using setEncoding()

toStringC14N
$c14nstr = $doc->toStringC14N($comment_flag,$xpath); A variation to toString, that returns the canonized form of the given document.
serialize
  $str = $doc->serialze($format);

Alternative form of toString(). This function name added to be more conformant with libxml2's examples.

serialize_c14n
  $c14nstr = $doc->serialize_c14n($comment_flag,$xpath);

Alternative form of toStringC14N().

toFile
  $state = $doc->toFile($filename, $format);

This function is similar to toString(), but it writes the document directly into a filesystem. This function is very useful, if one needs to store large documents.

The format parameter has the same behaviour as in toString().

toFH
  $state = $doc->toFH($fh, $format);

This function is similar to toString(), but it writes the document directly to a filehandler or a stream.

The format parameter has the same behaviour as in toString().

toStringHTML
  $str = $document->toStringHTML();

toStringHTML deparses the tree to a string as HTML. With this method indenting is automatic and managed by libxml2 internally.

serialize_html
  $str = $document->serialize_html();

Alternative form of toStringHTML().

is_valid
  $bool = $dom->is_valid();

Returns either TRUE or FALSE depending on whether the DOM Tree is a valid Document or not.

You may also pass in a XML::LibXML::Dtd object, to validate against an external DTD:

   if (!$dom->is_valid($dtd)) {
       warn("document is not valid!");
   }

validate
  $dom->validate();

This is an exception throwing equivalent of is_valid. If the document is not valid it will throw an exception containing the error. This allows you much better error reporting than simply is_valid or not.

Again, you may pass in a DTD object

documentElement
  $root = $dom->documentElement();

Returns the root element of the Document. A document can have just one root element to contain the documents data.

Optionaly one can use getDocumentElement.

setDocumentElement
  $dom->setDocumentElement( $root );

This function enables you to set the root element for a document. The function supports the import of a node from a different document tree.

createElement
  $element = $dom->createElement( $nodename );

This function creates a new Element Node bound to the DOM with the name $nodename.

createElementNS
  $element = $dom->createElementNS( $namespaceURI, $qname );

This function creates a new Element Node bound to the DOM with the name $nodename and placed in the given namespace.

createTextNode
  $text = $dom->createTextNode( $content_text );

As an equivalent of createElement, but it creates a Text Node bound to the DOM.

createComment
  $comment = $dom->createComment( $comment_text );

As an equivalent of createElement, but it creates a Comment Node bound to the DOM.

createAttribute
  $attrnode = $doc->createAttribute($name [,$value]);

Creates a new Attribute node.

createAttributeNS
  $attrnode = $doc->createAttributeNS( namespaceURI, $name [,$value] );

Creates an Attribute bound to a namespace.

createDocumentFragment
  $fragment = $doc->createDocumentFragment()

This function creates a DocumentFragment.

createCDATASection
  $cdata = $dom->create( $cdata_content );

Similar to createTextNode and createComment, this function creates a CDataSection bound to the current DOM.

createProcessingInstruction
  my $pi = $doc->createProcessingInstruction( $target, $data );

create a processing instruction node.

Since this method is quite long one may use its short form createPI().

createEntityReference
  my $entref = $doc->createEntityReference($refname);

If a document has a DTD specified, one can create entity references by using this function. If one wants to add a entity reference to the document, this reference has to be created by this function.

An entity reference is unique to a document and cannot be passed to other documents as other nodes can be passed.

NOTE: A text content containing something that looks like an entity reference, will not be expanded to a real entity reference unless it is a predefined entity

   my $string = "&foo;";
   $some_element->appendText( $string );
   print $some_element->textContent; # prints "&amp;foo;"

createInternalSubset
  $dtd = $document->createInternalSubset( $rootnode, $public, $system);

This function creates and adds an internal subset to the given document. Because the function automaticly adds the DTD to the document there is no need to add the created node explicitly to the document.

   my $document = XML::LibXML::Document->new();
   my $dtd      = $document->createInternalSubset( "foo", undef, "foo.dtd" );

will result in the following XML document:

  <?xml version="1.0"?>
   <!DOCTYPE foo SYSTEM "foo.dtd">

By setting the public parameter it is possible to set PUBLIC dtds to a given document. So

  my $document = XML::LibXML::Document->new();
  my $dtd      = $document->createInternalSubset( "foo", "-//FOO//DTD FOO 0.1//EN", undef );

will cause the following declaration to be created on the document:

  <?xml version="1.0"?>
  <!DOCTYPE foo PUBLIC "-//FOO//DTD FOO 0.1//EN">

createExternalSubset
  $dtd = $document->createExternalSubset( $rootnode, $public, $system);

This function is similar to createInternalSubset() but this DTD is considered to be external and is therefore not added to the document itself. Nevertheless it can be used for validation purposes.

importNode
  $document->importNode( $node );

If a node is not part of a document, it can be imported to another document. As specified in DOM Level 2 Specification the Node will not be altered or removed from its original document ($node->cloneNode(1) will get called implicitly).

NOTE: Don't try to use importNode() to import subtrees that contain an entity reference - even if the entity reference is the root node of the subtree. This will cause serious problems to your program. This is a limitation of libxml2 and not of XML::LibXML itself.

adoptNode
  $document->adoptNode( $node );

If a node is not part of a document, it can be imported to another document. As specified in DOM Level 3 Specification the Node will not be altered but it will removed from its original document.

After a document adopted a node, the node, its attributes and all its descendants belong to the new document. Because the node does not belong to the old document, it will be unlinked from its old location first.

NOTE: Don't try to adoptNode() to import subtrees that contain entity references - even if the entity reference is the root node of the subtree. This will cause serious problems to your program. This is a limitation of libxml2 and not of XML::LibXML itself.

externalSubset
  my $dtd = $doc->externalSubset;

If a document has an external subset defined it will be returned by this function.

NOTE Dtd nodes are no ordinary nodes in libxml2. The support for these nodes in XML::LibXML is still limited. In particular one may not want use common node function on doctype declaration nodes!

internalSubset
  my $dtd = $doc->internalSubset;

If a document has an internal subset defined it will be returned by this function.

NOTE Dtd nodes are no ordinary nodes in libxml2. The support for these nodes in XML::LibXML is still limited. In particular one may not want use common node function on doctype declaration nodes!

setExternalSubset
  $doc->setExternalSubset($dtd);

EXPERIMENTAL!

This method sets a DTD node as an external subset of the given document.

setInternalSubset
  $doc->setInternalSubset($dtd);

EXPERIMENTAL!

This method sets a DTD node as an internal subset of the given document.

removeExternalSubset
  my $dtd = $doc->removeExternalSubset();

EXPERIMENTAL!

If a document has an external subset defined it can be removed from the document by using this function. The removed dtd node will be returned.

removeInternalSubset
  my $dtd = $doc->removeInternalSubset();

EXPERIMENTAL!

If a document has an internal subset defined it can be removed from the document by using this function. The removed dtd node will be returned.

getElementsByTagName
  my @nodelist = $doc->getElementsByTagName($tagname);

Implements the DOM Level 2 function

In SCALAR context this function returns a XML::LibXML::NodeList object.

getElementsByTagNameNS
  my @nodelist = $doc->getElementsByTagName($nsURI,$tagname);

Implements the DOM Level 2 function

In SCALAR context this function returns a XML::LibXML::NodeList object.

getElementsByLocalName
  my @nodelist = $doc->getElementsByLocalName($localname);

This allows the fetching of all nodes from a given document with the given Localname.

In SCALAR context this function returns a XML::LibXML::NodeList object.

getElementsById
  my $node = $doc->getElementsById($id);

This allows the fetching of the node at a given position in the DOM.

Note: The Id of a node might change while manipulating the document.

indexElements
  $dom->indexElements();

This function causes libxml2 to stamp all elements in a document with their document position index which considerably speeds up XPath queries for large documents. It should only be used with static documents that won't be further changed by any DOM methods, because once a document is indexed, XPath will always prefer the index to other methods of determining the document order of nodes. XPath could therefore return improperly ordered node-lists when applied on a document that has been changed after being indexed. It is of course possible to use this method to re-index a modified document before using it with XPath again. This function is not a part of the DOM specification.

This function returns number of elements indexed, -1 if error occurred, or -2 if this feature is not available in the running libxml2.

 

AUTHORS

Matt Sergeant, Christian Glahn, =head1 VERSION

1.58  

COPYRIGHT

2001-2004, AxKit.com Ltd; 2002-2004 Christian Glahn, All rights reserved.


 

Index

NAME
SYNOPSIS
DESCRIPTION
AUTHORS
COPYRIGHT

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