java编程之xpath介绍

public static void Test1() throws Exception {
    Document document = Dom4jUtils.getDocument(Dom4jUtils.PATH);
    List<Node> list = document.selectNodes("//name");
    for (Node node : list) {
      //node是每一个元素具体的值
      //得到每一个元素具体的值
      String s = node.getText();
      System.out.println(s);
    }
  }

public static void Test2() throws Exception{
    Document document = Dom4jUtils.getDocument(Dom4jUtils.PATH);
    Node name1 = document.selectSingleNode("//p1[@id1='aaa']/name");
    //得到name的值
    String s1 = name1.getText();
    System.out.println(s1);
  }

<?xml version="1.0" encoding="UTF-8"?>

<student> 
 <stu> 
  <id>01</id> 
  <name>zhangsan</name> 
  <age>20</age> 
 </stu> 
 <stu> 
  <id>02</id> 
  <name>lisi</name> 
  <age>19</age> 
 </stu> 
</student>

package cn.qing.ov;
public class Student {
	private String id;
	private String name;
	private String age;
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	@Override
	  public String toString() {
		return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
	}
}

package cn.qing.service;
import java.io.FileOutputStream;
import java.io.Writer;
import java.util.List;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import cn.qing.ov.Student;
public class StuService {
	//增加
	public static void addStu(Student student) throws Exception {
		SAXReader saxReader = new SAXReader();
		Document document = saxReader.read("src/student.xml");
		Element root = document.getRootElement();
		//在根节点上添加stu
		Element stu = root.addElement("stu");
		//在stu标签上一次添加id，name，age
		Element id1 = stu.addElement("id");
		Element name1 = stu.addElement("name");
		Element age1 = stu.addElement("age");
		//在id，name，age，上依次添加值
		id1.setText(student.getId());
		name1.setText(student.getName());
		age1.setText(student.getAge());
		//回写到xml中
		OutputFormat format = OutputFormat.createPrettyPrint();
		XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/student.xml"),format);
		xmlWriter.write(document);
		xmlWriter.close();
	}
	//删除,根据学生ID进行删除
	/**
   * 
   * @param id
   * @throws Exception
   * 1.创建解析器
   * 2.获得document
   * 3.获取xml中的ID，使用xpath,返回一个list集合
   * 4.遍历list，判断集合里的值是否和传进来的id相同
   * 5.如果相同，把id所在的stu删除
   * 6.回写
   */
	public static void delStu(String id) throws Exception {
		SAXReader saxReader = new SAXReader();
		Document document = saxReader.read("src/student.xml");
		List<Node> list = document.selectNodes("//id");
		for (Node node : list) {
			String idv = node.getText();
			//判断是否和传递的值相同
			if(idv.equals(id)) {
				//得到stu的节点
				Element stu = node.getParent();
				//删除是通过父节点进行删除
				Element student = stu.getParent();
				student.remove(stu);
			}
		}
		OutputFormat format =OutputFormat.createPrettyPrint();
		XMLWriter xmlWriter = new XMLWriter(new FileOutputStream("src/student.xml"),format);
		xmlWriter.write(document);
		xmlWriter.close();
	}
	//查询
	public static Student selStu(String id) throws Exception {
		SAXReader saxReader = new SAXReader();
		Document document = saxReader.read("src/student.xml");
		List<Node> list = document.selectNodes("//id");
		Student student = new Student();
		for (Node node : list) {
			//node 是每一个id的值
			String idv = node.getText();
			if(idv.equals(id)) {
				Element stu = node.getParent();
				String namev = stu.element("name").getText();
				String agev = stu.element("age").getText();
				student.setId(idv);
				student.setName(namev);
				student.setAge(agev);
			}
		}
		return student;
	}
}

package cn.qing.test;
import cn.qing.ov.Student;
import cn.qing.service.StuService;
public class Test {
	public static void main(String[] args) throws Exception {
		//testAdd();
		//testDel();
		testSel();
	}
	//测试添加方法
	public static void testAdd() throws Exception {
		//创建student对象
		Student stu = new Student();
		stu.setId("03");
		stu.setName("wangwu");
		stu.setAge("18");
		StuService.addStu(stu);
	}
	//测试删除方法
	public static void testDel() throws Exception {
		StuService.delStu("03");
	}
	//测试查询方法
	public static void testSel() throws Exception {
		Student student = StuService.selStu("02");
		System.out.println(student.toString());
	}
}