xpath_getelem.html

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<TITLE>Finding Elements by Absolute Location in a DOM Document Using XPath
(Java Developers Almanac Example)
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  <h3>
    e548.  
    Finding Elements by Absolute Location in a DOM Document Using XPath</h3>

XPath is a expression language for selecting nodes in an XML file.
The specification for XPath can be found at
//<a href="http://www.w3.org/TR/xpath"><font size="-1">http://www.w3.org/TR/xpath</font></a>.

Note: This example uses the XPath packages (<code>org.apache.xpath.*</code>)
available in J2SE 1.4.  However, these packages are not yet part of
the Java 2 API and so this example may not work in future versions of
J2SE.


<pre>
    // Get the root element
    String xpath = "/*";
    
    // Get all e elements in the document
    xpath = "//e";
    
    // Get the first e element in the document
    xpath = "(//e)[1]";
    
    // Get the last e element in the document
    xpath = "(//e)[last()]";
    
    // Get only e elements directly under an elem1 element
    xpath = "//elem1/e";
    
    // Get only e elements anywhere under an elem1 element
    xpath = "//elem1//e";
    
    // Get all e elements directly under either the root or an elem2 element .
    // The | operator combines two node sets.
    xpath = "/*/e | //elem2/e";
    
    // Get all elements with more than one e child elements
    xpath = "//*[count(e)&gt;1]";
</pre>


XPath does not yet support regular expressions to match element names.
Hoever, it is possible to perform some very simple pattern matches on
element names.



<pre>
    // Get all elements whose name starts with el
    xpath = "//*[starts-with(name(), 'el')]";
    
    // Get all elements whose name contains with lem1
    xpath = "//*[contains(name(), 'lem1')]";
</pre>


<pre>
    // Create a document; this method is implemented in
    // <a href="../javax.xml.parsers/BasicDom.html" class="eglink"><font size="-1"><b>e510</b> The Quintessential Program to Create a DOM Document from an XML File</font></a>
    Document doc = <font color="#0066ff"><i>parseXmlFile</i></font>(<font color="#0066ff"><i>"infilename.xml"</i></font>, <font color="#0066ff"><i>false</i></font>);
    
    
    try {
        NodeList nodelist = org.apache.xpath.XPathAPI.selectNodeList(doc, xpath);
    
        // Process the elements in the nodelist
        for (int i=0; i&lt;nodelist.getLength(); i++) {
            // Get element
            Element elem = (Element)nodelist.item(i);
        }
    } catch (javax.xml.transform.TransformerException e) {
    }
</pre>

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