XPath 对xml文件操作

常见语法：

stu.xml文件：

<?xml version="1.0"?>
<students>
 <student id='001'>
    <name>zhangsan</name>
    <age>20</age>
 </student>
 <student id='002'>
    <name>李四</name>
    <age>23</age>
    </student>
 <student id="003">
    <name>wangwu</name>
    <age>21</age>
 </student>
 <student id="004">
    <name>zhaoliu</name>
    <age>26</age>
 </student>
 <haha>hello,world</haha>
</students>

类XPathDemo：

package day03;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class XPathDemo {

	/**
	 * @param args
	 * @throws DocumentException 
	 */
	public static void main(String[] args) throws DocumentException {
		// TODO Auto-generated method stub
	 
		SAXReader reader=new SAXReader();
		File file=new File("stu.xml");
		Document document=reader.read(file);
		
		 Element rootElement=document.getRootElement(); 
		 /*String xpath="students/student";
		 List list=document.selectNodes(xpath);*/
		 //与下面等价
		 String xpath="/students/student";
		 
		 //String xpath="//student"; 所有的student
		 
		 
		 
		 List list=rootElement.selectNodes(xpath);
		 
		 
		 System.out.println(list.size()+"....");
		 getStudentById(document,"002");
	}
	
	public static void getStudentById(Document document, String id){
		String xpath="//student[@id="+id+"]";
		Element stuElement=(Element)document.selectSingleNode(xpath);
		System.out.println(stuElement.elementText("name"));
	}
     
	
}

注意： java.lang.NoClassDefFoundError这个错误就应该想到是不是包没引全，这里要引入jaxven.jar