XPath JAVA用法总结及代码样例

package com.taoxi.java.xpath;

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

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class XPathDemo {
    private static Document doc;
    private static XPath xpath;

    public static void main(String[] args) throws Exception {
        init();
        getRootEle();
        getChildEles();
        getPartEles();
        haveChildsEles();
        getLevelEles();
        getAttrEles();

        //打印根节点下的所有元素节点
        System.out.println(doc.getDocumentElement().getChildNodes().getLength());
        NodeList nodeList = doc.getDocumentElement().getChildNodes();
        for (int i = 0; i < nodeList.getLength(); i++) {
            if (nodeList.item(i).getNodeType() == Node.ELEMENT_NODE) {
                System.out.print(nodeList.item(i).getNodeName() + " ");
            }
        }
    }

    // 初始化Document、XPath对象
    public static void init() throws Exception {
        // 创建Document对象
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setValidating(false);
        DocumentBuilder db = dbf.newDocumentBuilder();
        //两种加载资源文件的方法
//        InputStream resourceAsStream = XPathDemo.class.getResourceAsStream("/demo.xml");
        InputStream resourceAsStream = XPathDemo.class.getClassLoader().getResourceAsStream("demo.xml");
        doc = db.parse(resourceAsStream);

        // 创建XPath对象
        XPathFactory factory = XPathFactory.newInstance();
        xpath = factory.newXPath();
    }

    // 获取根元素
    // 表达式可以更换为/*,/rss
    public static void getRootEle() throws XPathExpressionException {
        Node node = (Node) xpath.evaluate("/rss", doc, XPathConstants.NODE);
        System.out.println(node.getNodeName() + "--------"
                + node.getNodeValue());
    }

    // 获取子元素并打印
    public static void getChildEles() throws XPathExpressionException {
        NodeList nodeList = (NodeList) xpath.evaluate("/rss/channel/*", doc,
                XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.print(nodeList.item(i).getNodeName() + " ");
        }
        System.out.println();
    }

    // 获取部分元素
    // 只获取元素名称为title的元素
    public static void getPartEles() throws XPathExpressionException {
        NodeList nodeList = (NodeList) xpath.evaluate("//*[name() = ‘title‘]",
                doc, XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.print(nodeList.item(i).getNodeName() + "-->"
                    + nodeList.item(i).getTextContent());
        }
        System.out.println();
    }

    // 获取包含子节点的元素
    public static void haveChildsEles() throws XPathExpressionException {
        NodeList nodeList = (NodeList) xpath.evaluate("//*[*]", doc,
                XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.print(nodeList.item(i).getNodeName() + " ");
        }
        System.out.println();
    }

    // 获取指定层级的元素
    public static void getLevelEles() throws XPathExpressionException {
        NodeList nodeList = (NodeList) xpath.evaluate("/*/*/*/*", doc,
                XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.print(nodeList.item(i).getNodeName() + "-->"
                    + nodeList.item(i).getTextContent() + " ");
        }
        System.out.println("-----------------------------");
    }

    // 获取指定属性的元素
    // 获取所有大于指定价格的书箱
    public static void getAttrEles() throws XPathExpressionException {
        NodeList nodeList = (NodeList) xpath.evaluate("//bookstore/book[price>35.00]/title", doc,
                XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.print(nodeList.item(i).getNodeName() + "-->"
                    + nodeList.item(i).getTextContent() + " ");
        }
        System.out.println();
    }
}

<?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>
    <college name="c1">
        <class name="class1">
            <student name="stu1" sex=‘male‘ age="21" />
            <student name="stu2" sex=‘female‘ age="20" />
            <student name="stu3" sex=‘female‘ age="20" />
        </class>
    </college>
    <bookstore>
        <book>
            <title lang="eng">Harry Potter</title>
            <price>29.99</price>
        </book>
        <book>
            <title lang="eng">Learning XML</title>
            <price>39.95</price>
        </book>
    </bookstore>
</rss>