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<html><head><title>XML::Grove (Perl and XML)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Erik T. Ray and Jason McIntosh" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="059600205XL" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl and XML" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl & XML" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch06_05.htm"><img alt="Previous" border="0" src="../gifs/txtpreva.gif" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch07_01.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr></table></div><h2 class="sect1">6.6. XML::Grove</h2><p>The <a name="INDEX-512" /> <a name="INDEX-513" />last object model we'llexamine before jumping into standards-based solutions is Ken<a name="INDEX-514" />MacLeod's<tt class="literal">XML::Grove</tt>. Like<tt class="literal">XML::SimpleObject</tt>, it takes the<tt class="literal">XML::Parser</tt> output in tree mode and changes itinto an object hierarchy. The difference is that each node type isrepresented by a different class. Therefore, an element would bemapped to <tt class="literal">XML::Grove::Element</tt>, a processinginstruction to <tt class="literal">XML::Grove::PI</tt>, and so on. Textnodes are still scalar values.</p><p>Another feature of this module is that the declarations in theinternal subset are captured in lists accessible through the<tt class="literal">XML::Grove</tt> object. Every entity or notationdeclaration is available for your perusal. For example, the followingprogram counts the distribution of elements and other nodes, and thenprints a list of node types and their frequency.</p><p>First, we initialize the parser with the style"grove" (to tell<tt class="literal">XML::Parser</tt> that it needs to use<tt class="literal">XML::Parser::Grove</tt> to process its output):</p><blockquote><pre class="code">use XML::Parser;use XML::Parser::Grove;use XML::Grove;my $parser = XML::Parser->new( Style => 'grove', NoExpand => '1' );my $grove = $parser->parsefile( shift @ARGV );</pre></blockquote><p>Next, we access the contents of the grove by calling the<tt class="literal">contents( )</tt> method. This method returns a listincluding the root element and any comments or PIs outside of it. Asubroutine called <tt class="literal">tabulate( )</tt> counts nodes anddescends recursively through the tree. Finally, the results areprinted:</p><blockquote><pre class="code"># tabulate elements and other nodesmy %dist;foreach( @{$grove->contents} ) { &tabulate( $_, \%dist );}print "\nNODES:\n\n";foreach( sort keys %dist ) { print "$_: " . $dist{$_} . "\n";}</pre></blockquote><p>Here is the subroutine that handles each node in the tree. Since eachnode is a different class, we can use <tt class="literal">ref( )</tt> toget the type. Attributes are not treated as nodes in this model, butare available through the element class's method<tt class="literal">attributes( )</tt> as a hash. The call to<tt class="literal">contents( )</tt> allows the routine to continueprocessing the element's children:</p><blockquote><pre class="code"># given a node and a table, find out what the node is, add to the count,# and recurse if necessary#sub tabulate { my( $node, $table ) = @_; my $type = ref( $node ); if( $type eq 'XML::Grove::Element' ) { $table->{ 'element' }++; $table->{ 'element (' . $node->name . ')' }++; foreach( keys %{$node->attributes} ) { $table->{ "attribute ($_)" }++; } foreach( @{$node->contents} ) { &tabulate( $_, $table ); } } elsif( $type eq 'XML::Grove::Entity' ) { $table->{ 'entity-ref (' . $node->name . ')' }++; } elsif( $type eq 'XML::Grove::PI' ) { $table->{ 'PI (' . $node->target . ')' }++; } elsif( $type eq 'XML::Grove::Comment' ) { $table->{ 'comment' }++; } else { $table->{ 'text-node' }++ }}</pre></blockquote><p>Here's a typical result, when run<a name="INDEX-515" /> <a name="INDEX-516" /> on anXML<a name="INDEX-517" />datafile:</p><blockquote><pre class="code">NODES:PI (a): 1attribute (date): 1attribute (style): 12attribute (type): 2element: 30element (category): 2element (inventory): 1element (item): 6element (location): 6element (name): 12element (note): 3text-node: 100</pre></blockquote><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch06_05.htm"><img alt="Previous" border="0" src="../gifs/txtpreva.gif" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img alt="Home" border="0" src="../gifs/txthome.gif" /></a></td><td align="right" valign="top" width="228"><a href="ch07_01.htm"><img alt="Next" border="0" src="../gifs/txtnexta.gif" /></a></td></tr><tr><td align="left" valign="top" width="228">6.5. XML::TreeBuilder</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img alt="Book Index" border="0" src="../gifs/index.gif" /></a></td><td align="right" valign="top" width="228">7. DOM</td></tr></table></div><hr width="684" align="left" /><img alt="Library Navigation Links" border="0" src="../gifs/navbar.gif" usemap="#library-map" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. 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