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XML::DOM - A perl module for building DOM Level 1 compliant document structures
use XML::DOM;
my $parser = new XML::DOM::Parser;
my $doc = $parser->parsefile ("file.xml");
# print all HREF attributes of all CODEBASE elements
my $nodes = $doc->getElementsByTagName ("CODEBASE");
my $n = $nodes->getLength;
for (my $i = 0; $i < $n; $i++)
{
my $node = $nodes->item ($i);
my $href = $node->getAttributeNode ("HREF");
print $href->getValue . "\n";
}
# Print doc file
$doc->printToFile ("out.xml");
# Print to string print $doc->toString;
# Avoid memory leaks - cleanup circular references for garbage collection $doc->dispose;
XML::DOM::Parser is derived from XML::Parser. It parses XML strings or files and builds a data structure that conforms to the API of the Document Object Model as described at http://www.w3.org/TR/REC-DOM-Level-1. See the XML::Parser manpage for other available features of the XML::DOM::Parser class. Note that the 'Style' property should not be used (it is set internally.)
The XML::Parser NoExpand option is more or less supported, in that it will generate EntityReference objects whenever an entity reference is encountered in character data. I'm not sure how useful this is. Any comments are welcome.
As described in the synopsis, when you create an XML::DOM::Parser object, the parse and parsefile methods create an XML::DOM::Document object from the specified input. This Document object can then be examined, modified and written back out to a file or converted to a string.
When using XML::DOM with XML::Parser version 2.19 and up, setting the XML::DOM::Parser option KeepCDATA to 1 will store CDATASections in CDATASection nodes, instead of converting them to Text nodes. Subsequent CDATASection nodes will be merged into one. Let me know if this is a problem.
When using XML::Parser 2.27 and above, you can suppress expansion of parameter entity references (e.g. %pent;) in the DTD, by setting ParseParamEnt to 1 and ExpandParamEnt to 0. See Hidden Nodes for details.
A Document has a tree structure consisting of Node objects. A Node may contain other nodes, depending on its type. A Document may have Element, Text, Comment, and CDATASection nodes. Element nodes may have Attr, Element, Text, Comment, and CDATASection nodes. The other nodes may not have any child nodes.
This module adds several node types that are not part of the DOM spec (yet.) These are: ElementDecl (for <!ELEMENT ...> declarations), AttlistDecl (for <!ATTLIST ...> declarations), XMLDecl (for <?xml ...?> declarations) and AttDef (for attribute definitions in an AttlistDecl.)
In addition, the XML::DOM module contains the following nodes that are not part of the DOM Level 1 Specification:
Other classes that are part of the DOM Level 1 Spec:
Other classes that are not part of the DOM Level 1 Spec:
UNKNOWN_NODE (0) The node type is unknown (not part of DOM)
ELEMENT_NODE (1) The node is an Element. ATTRIBUTE_NODE (2) The node is an Attr. TEXT_NODE (3) The node is a Text node. CDATA_SECTION_NODE (4) The node is a CDATASection. ENTITY_REFERENCE_NODE (5) The node is an EntityReference. ENTITY_NODE (6) The node is an Entity. PROCESSING_INSTRUCTION_NODE (7) The node is a ProcessingInstruction. COMMENT_NODE (8) The node is a Comment. DOCUMENT_NODE (9) The node is a Document. DOCUMENT_TYPE_NODE (10) The node is a DocumentType. DOCUMENT_FRAGMENT_NODE (11) The node is a DocumentFragment. NOTATION_NODE (12) The node is a Notation.
ELEMENT_DECL_NODE (13) The node is an ElementDecl (not part of DOM) ATT_DEF_NODE (14) The node is an AttDef (not part of DOM) XML_DECL_NODE (15) The node is an XMLDecl (not part of DOM) ATTLIST_DECL_NODE (16) The node is an AttlistDecl (not part of DOM)
Usage:
if ($node->getNodeType == ELEMENT_NODE)
{
print "It's an Element";
}
Not In DOM Spec: The DOM Spec does not mention UNKNOWN_NODE and, quite frankly, you should never encounter it. The last 4 node types were added to support the 4 added node classes.
The ignoreReadOnly method sets the global IgnoreReadOnly flag and returns its previous value. The getIgnoreReadOnly method simply returns its current value.
my $oldIgnore = XML::DOM::ignoreReadOnly (1);
eval {
... do whatever you want, catching any other exceptions ...
};
XML::DOM::ignoreReadOnly ($oldIgnore); # restore previous value
Another way to do it, using a local variable:
{ # start new scope
local $XML::DOM::IgnoreReadOnly = 1;
... do whatever you want, don't worry about exceptions ...
} # end of scope ($IgnoreReadOnly is set back to its previous value)
The XML spec states that ``Names'' starting with (X|x)(M|m)(L|l) are reserved for future use. (Amusingly enough, the XML version of the XML spec (REC-xml-19980210.xml) breaks that very rule by defining an ENTITY with the name 'xmlpio'.) A ``Name'' in this context means the Name token as found in the BNF rules in the XML spec.
XML::DOM only checks for errors when you modify the DOM tree, not when the DOM tree is built by the XML::DOM::Parser.
<empty/> or <empty attr="val"/>
XML::DOM uses this style by default for all Elements.
<empty></empty> or <empty attr="val"></empty>
<empty /> or <empty attr="val" />
This style is sometimes desired when using XHTML. (Note the extra space before the slash ``/'') See <http://www.w3.org/TR/xhtml1> Appendix C for more details.
By default XML::DOM compresses all empty Element tags (style 0.) You can control which style is used for a particular Element by calling XML::DOM::setTagCompression with a reference to a function that takes 2 arguments. The first is the tag name of the Element, the second is the XML::DOM::Element that is being printed. The function should return 0, 1 or 2 to indicate which style should be used to print the empty tag. E.g.
XML::DOM::setTagCompression (\&my_tag_compression);
sub my_tag_compression
{
my ($tag, $elem) = @_;
# Print empty br, hr and img tags like this: <br />
return 2 if $tag =~ /^(br|hr|img)$/;
# Print other empty tags like this: <empty></empty>
return 1;
}
The DOM Spec says: Applications must encode DOMString using UTF-16 (defined in Appendix C.3 of [UNICODE] and Amendment 1 of [ISO-10646]). In this implementation we use plain old Perl strings encoded in UTF-8 instead of UTF-16.
Also, subsequent Text nodes are always merged at parse time. Text nodes that are added later can be merged with the normalize method. Consider using the addText method when adding Text nodes.
When it is parsing the contents of the external entities, it *DOES* still add the nodes to the DocumentType, but it marks these nodes by setting the 'Hidden' property. In addition, it adds an EntityReference node to the DocumentType node.
When printing the DocumentType node (or when using to_expat() or to_sax()), the 'Hidden' nodes are suppressed, so you will see the parameter entity reference instead of the contents of the external entities. See test case t/dom_extent.t for an example.
The reason for adding the 'Hidden' nodes to the DocumentType node, is that the nodes may contain <!ENTITY> definitions that are referenced further in the document. (Simply not adding the nodes to the DocumentType could cause such entity references to be expanded incorrectly.)
Note that you need XML::Parser 2.27 or higher for this to work correctly.
The DOM Level 1 specification at <http://www.w3.org/TR/REC-DOM-Level-1>
The XML spec (Extensible Markup Language 1.0) at <http://www.w3.org/TR/REC-xml>
The XML::Parser and XML::Parser::Expat manual pages.
XML::LibXML also provides a DOM Parser, and is significantly faster than XML::DOM, and is under active development. It requires that you download the Gnome libxml library.
XML::GDOME will provide the DOM Level 2 Core API, and should be as fast as XML::LibXML, but more robust, since it uses the memory management functions of libgdome. For more details see <http://tjmather.com/xml-gdome/>
Send patches to T.J. Mather at <tjmather@maxmind.com>.
Paid support is available from directly from the maintainers of this package. Please see <http://www.maxmind.com/app/opensourceservices> for more details.
Thanks to Clark Cooper for his help with the initial version.
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