xpath读取xml文档

package test;


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.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() + " ");
// }
// nodeList.
}
}


// 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();
doc = db.parse(new FileInputStream(new File("src\\main\\test\\test\\test.xml")));
// doc = db.parse(new FileInputStream(new File("test.xml")));

// 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>