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Sat Feb 14 18:55:40 MST 2004 John Fleck <jfleck@inkstain.net> * doc/tutorial/xmltutorial.xml * doc/tutorial/xmltutorial.pdf * doc/tutorial/*.html Fix bug in XPath example in the tutorial, thanks to Carlos, whose last name I don't know, for pointing this out
55 lines
6.1 KiB
HTML
55 lines
6.1 KiB
HTML
<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Retrieving Element Content</title><meta name="generator" content="DocBook XSL Stylesheets V1.61.2"><link rel="home" href="index.html" title="Libxml Tutorial"><link rel="up" href="index.html" title="Libxml Tutorial"><link rel="previous" href="ar01s03.html" title="Parsing the file"><link rel="next" href="ar01s05.html" title="Using XPath to Retrieve Element Content"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Retrieving Element Content</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ar01s03.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ar01s05.html">Next</a></td></tr></table><hr></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="xmltutorialgettext"></a>Retrieving Element Content</h2></div></div><div></div></div><p><a class="indexterm" name="id2447408"></a>
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Retrieving the content of an element involves traversing the document
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tree until you find what you are looking for. In this case, we are looking
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for an element called "keyword" contained within element called "story". The
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process to find the node we are interested in involves tediously walking the
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tree. We assume you already have an xmlDocPtr called <tt class="varname">doc</tt>
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and an xmlNodPtr called <tt class="varname">cur</tt>.</p><p>
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</p><pre class="programlisting">
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<a name="getchildnode"></a><img src="images/callouts/1.png" alt="1" border="0">cur = cur->xmlChildrenNode;
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<a name="huntstoryinfo"></a><img src="images/callouts/2.png" alt="2" border="0">while (cur != NULL) {
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if ((!xmlStrcmp(cur->name, (const xmlChar *)"storyinfo"))){
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parseStory (doc, cur);
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}
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cur = cur->next;
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}
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</pre><p>
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</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><a href="#getchildnode"><img src="images/callouts/1.png" alt="1" border="0"></a> </td><td valign="top" align="left"><p>Get the first child node of <tt class="varname">cur</tt>. At this
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point, <tt class="varname">cur</tt> points at the document root, which is
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the element "story".</p></td></tr><tr><td width="5%" valign="top" align="left"><a href="#huntstoryinfo"><img src="images/callouts/2.png" alt="2" border="0"></a> </td><td valign="top" align="left"><p>This loop iterates through the elements that are children of
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"story", looking for one called "storyinfo". That
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is the element that will contain the "keywords" we are
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looking for. It uses the <span class="application">libxml</span> string
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comparison
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function, <tt class="function"><a href="http://xmlsoft.org/html/libxml-parser.html#XMLSTRCMP" target="_top">xmlStrcmp</a></tt>. If there is a match, it calls the function <tt class="function">parseStory</tt>.</p></td></tr></table></div><p>
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</p><p>
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</p><pre class="programlisting">
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void
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parseStory (xmlDocPtr doc, xmlNodePtr cur) {
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xmlChar *key;
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<a name="anothergetchild"></a><img src="images/callouts/1.png" alt="1" border="0"> cur = cur->xmlChildrenNode;
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<a name="findkeyword"></a><img src="images/callouts/2.png" alt="2" border="0"> while (cur != NULL) {
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if ((!xmlStrcmp(cur->name, (const xmlChar *)"keyword"))) {
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<a name="foundkeyword"></a><img src="images/callouts/3.png" alt="3" border="0"> key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
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printf("keyword: %s\n", key);
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xmlFree(key);
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}
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cur = cur->next;
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}
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return;
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}
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</pre><p>
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</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><a href="#anothergetchild"><img src="images/callouts/1.png" alt="1" border="0"></a> </td><td valign="top" align="left"><p>Again we get the first child node.</p></td></tr><tr><td width="5%" valign="top" align="left"><a href="#findkeyword"><img src="images/callouts/2.png" alt="2" border="0"></a> </td><td valign="top" align="left"><p>Like the loop above, we then iterate through the nodes, looking
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for one that matches the element we're interested in, in this case
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"keyword".</p></td></tr><tr><td width="5%" valign="top" align="left"><a href="#foundkeyword"><img src="images/callouts/3.png" alt="3" border="0"></a> </td><td valign="top" align="left"><p>When we find the "keyword" element, we need to print
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its contents. Remember that in <span class="acronym">XML</span>, the text
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contained within an element is a child node of that element, so we
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turn to <tt class="varname">cur->xmlChildrenNode</tt>. To retrieve it, we
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use the function <tt class="function"><a href="http://xmlsoft.org/html/libxml-tree.html#XMLNODELISTGETSTRING" target="_top">xmlNodeListGetString</a></tt>, which also takes the <tt class="varname">doc</tt> pointer as an argument. In this case, we just print it out.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td colspan="2" align="left" valign="top"><p>Because <tt class="function">xmlNodeListGetString</tt> allocates
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memory for the string it returns, you must use
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<tt class="function">xmlFree</tt> to free it.</p></td></tr></table></div></td></tr></table></div><p>
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</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ar01s03.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="index.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ar01s05.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Parsing the file </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Using XPath to Retrieve Element Content</td></tr></table></div></body></html>
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