java通過XPath解析xml節點

import java.io.File;
import java.io.FileInputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class FindElementsByAbsoluteLocationWithXPath {

public static void main(String[] args) throws Exception {

    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    dbf.setValidating(false);
    DocumentBuilder db = dbf.newDocumentBuilder();

    Document doc = db.parse(new FileInputStream(new File("in.xml")));

    XPathFactory factory = XPathFactory.newInstance();

    XPath xpath = factory.newXPath();

    String expression;
    Node node;
    NodeList nodeList;

    // 1. root element
    expression = "/*";
    node = (Node) xpath.evaluate(expression, doc, XPathConstants.NODE);
    System.out.println("1. " + node.getNodeName());

    // 2. root element (by name)
    expression = "/rss";
    node = (Node) xpath.evaluate(expression, doc, XPathConstants.NODE);
    System.out.println("2. " + node.getNodeName());

    // 3. element under rss
    expression = "/rss/channel";
    node = (Node) xpath.evaluate(expression, doc, XPathConstants.NODE);
    System.out.println("3. " + node.getNodeName());

    // 4. all elements under rss/channel
    expression = "/rss/channel/*";
    nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
    System.out.print("4. ");
    for (int i = 0; i < nodeList.getLength(); i++) {
        System.out.print(nodeList.item(i).getNodeName() + " ");
    }
    System.out.println();

    // 5. all title elements in the document
    expression = "//title";
    nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
    System.out.print("5. ");
    for (int i = 0; i < nodeList.getLength(); i++) {
        System.out.print(nodeList.item(i).getNodeName() + " ");
    }
    System.out.println();

    // 6. all elements in the document except title
    expression = "//*[name() != 'title']";
    nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
    System.out.print("6. ");
    for (int i = 0; i < nodeList.getLength(); i++) {
        System.out.print(nodeList.item(i).getNodeName() + " ");
    }
    System.out.println();

    // 7. all elements with at least one child element
    expression = "//*[*]";
    nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
    System.out.print("7. ");
    for (int i = 0; i < nodeList.getLength(); i++) {
        System.out.print(nodeList.item(i).getNodeName() + " ");
    }
    System.out.println();

    // 8. all level-5 elements (the root being at level 1)
    expression = "/*/*/*/*";
    nodeList = (NodeList) xpath.evaluate(expression, doc, XPathConstants.NODESET);
    System.out.print("8. ");
    for (int i = 0; i < nodeList.getLength(); i++) {
        System.out.print(nodeList.item(i).getNodeName() + " ");
    }
    System.out.println();

}


}</pre> 


 Input: 

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
    <channel>
        <title>Java Tutorials and Examples 2</title>
        <language>en-us</language>
        <item>
            <title><![CDATA[Java Tutorials 2]]></title>
            <link>http://www.javacodegeeks.com/</link>
        </item>
        <item>
            <title><![CDATA[Java Examples 2]]></title>
            <link>http://examples.javacodegeeks.com/</link>
        </item>
    </channel>
</rss>
 


 輸出： 

1. rss


rss
channel
title language item item 
title title title 
rss channel language item link item link 
rss channel item item 
title link title link </pre>