Xpath用法

package cn.hncu.dom4j;

import java.io.FileOutputStream;
import java.io.FileWriter;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;
import org.junit.Test;

public class Dom4jDemo {
@Test
public void readDemo() throws Exception{
//声明SAXReader核心读取(xml)类，并获得dom对象
SAXReader sax = new SAXReader();
Document dom = sax.read("./xml5/users.xml");//路径（可以自己换）
//获取根元素
Element root = dom.getRootElement();
//获取里面的第一个子元素
Element user = root.element("user");
String id = user.attributeValue("id");
System.out.println(id);
String name = user.element("name").getText();//获取子元素中的文本内容--法1
String age = user.elementText("age");//获取子元素中的文本内容--法2
System.out.println(name+","+age);
}

//显示(遍历)所有的用户
@Test
public void readAll() throws Exception{
SAXReader reader = new SAXReader();
Document document = reader.read("./xml5/users.xml");
Element root = document.getRootElement();
Iterator<Element> it = root.elementIterator();
while(it.hasNext()){
Element e = it.next();
String id = e.attributeValue("id");
String name = e.element("name").getText();
String age = e.elementText("age");
System.out.println("id:"+id+",name:"+name+",age:"+age);
}
}

//添加一个<user>元素
@Test
public void addElement() throws Exception{
SAXReader reader = new SAXReader();
Document document = reader.read("./xml5/users.xml");
Element root = document.getRootElement();

Element e = root.addElement("user");
e.addAttribute("id", "C003");
Element eName = e.addElement("name");
eName.setText("玛丽");
Element eAge = e.addElement("age");
eAge.setText("24");

//要把内存中的dom对象写到目的地(磁盘)
//法1---功能有限
//        FileWriter fw = new FileWriter("./xml5/users.xml");
//        document.write(fw);
//        fw.close();
//法2---功能更强
//XMLWriter writer = new XMLWriter( System.out );//输出到控制台
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("utf-8");
XMLWriter writer = new XMLWriter(new FileWriter("./xml5/users.xml"),format );//以指定的输出格式，把dom输出到指定的目的地(文件)
writer.write(document);
writer.close();

}

//删除最后一个<user>元素
@Test
public void delElement() throws Exception{
SAXReader reader = new SAXReader();
Document document = reader.read("./xml5/users.xml");
Element root = document.getRootElement();

List<Element> list = root.elements();
Element e = list.get(list.size()-1);
e.getParent().remove(e);

//保存
XMLWriter writer = new XMLWriter(new FileOutputStream("./xml5/users.xml"));
writer.write(document);
writer.close();
}

//从零开始创建一个xml文档
@Test
public void createNewXml() throws Exception{
Document document = DocumentHelper.createDocument();
Element root = document.addElement( "hncu" );
root.addElement("department").addAttribute("id", "hnuc001").addElement("xky").setText("信息科学与工程学院");

//保存
XMLWriter w = new XMLWriter(new FileOutputStream("./xml5/hncu.xml"));
w.write(document);
}

//xpath用法
@Test
public void xpathDemo() throws Exception{
SAXReader sax = new SAXReader();
Document dom = sax.read("./xml5/contact.xml");
//String xpath="/*/name";//第一个"/"表示当前元素
//String xpath="//contact/name";//选择contact下面的name(儿子)
//String xpath="//aaa/preceding::*";//选择<aaa>前面的所有元素
String xpath="//*[@id]";//选择具有id属性的所有元素
Element root = dom.getRootElement();
System.out.println(root.getName());
List<Element> list = root.selectNodes(xpath);
for(Element e:list){
System.out.println(e.getName()+"---"+e.getText());
}
}

//xpath用法
@Test
public void xpathDemo2() throws Exception{
SAXReader sax = new SAXReader();
Document dom = sax.read("./xml5/contact.xml");
Scanner sc = new Scanner(System.in);
String name = sc.nextLine();
name = name.toLowerCase();
String pwd = sc.nextLine();
pwd = pwd.toLowerCase();

//String xpath="//user[@name][@pwd]";//选择同时包含name和pwd属性的user元素
//String xpath="//user[@name='Jack'][@pwd='1234']";//选择name='Jack'且pwd='1234'那个user元素
//String xpath="//user[@name='"+name+"'][@pwd='"+pwd+"']";//选择name='Jack'且pwd='1234'那个user元素
String xpath="//user[fn:lower-case(@name)='"+name+"'][fn:lower-case(@pwd)='"+pwd+"']";//选择name='Jack'且pwd='1234'那个user元素
List<Element> list = dom.selectNodes(xpath);
System.out.println(list.size());
//		for(Element e:list){
//			System.out.println(e.getName());
//			List<Element> eList = e.selectNodes("//contact/name");
//			for(Element e2:eList){
//				System.out.println(e2.getText());
//			}
//		}
}

}