XML案例（使用DOM4J解析XML文档）

1.Demo1.java

package cn.itcast.dom4j;

import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.List;

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 Demo1 {

// 读取xml文档第二本书的：<书名>Java</书名>
@Test
public void test1() throws Exception {
SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));
Element root = document.getRootElement();
Element book = (Element) root.elements("书").get(1);
String value = book.element("书名").getText();
System.out.println(value);
}

// 读取xml文档第二本书的属性：<书名 name="xx">Java</书名>
@Test
public void test2() throws Exception {

SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));
Element root = document.getRootElement();
Element book = (Element) root.elements("书").get(1);
String value = book.element("书名").attributeValue("name");
System.out.println(value);

}

// 在第一本书上添加一个新的售价：<售价>211元</售价>
@Test
public void addtest() throws Exception {

SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));
Element root = document.getRootElement();
Element book = (Element) root.elements("书").get(0);
book.addElement("售价").setText("211元");

OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("gb2312");

XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),
format);
writer.write(document);
writer.close();
}

// 在第一本书指定位置上添加一个新的售价：<售价>209元</售价>
@Test
public void addtest2() throws Exception {

SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));

Element book = (Element) document.getRootElement().element("书");
List list = book.elements();// [书名，作者，售价，售价]

Element price = DocumentHelper.createElement("售价");
price.setText("209元");

list.add(2, price);

OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("gb2312");

XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),
format);
writer.write(document);
writer.close();
}

// 删除上面添加的售价节点
@Test
public void delete() throws Exception {
SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));

Element price = (Element) document.getRootElement().element("书").element("售价");
price.getParent().remove(price);

OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("gb2312");

XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),
format);
writer.write(document);
writer.close();
}

// 删除上面添加的售价节点
@Test
public void update() throws Exception {
SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));

Element book = (Element) document.getRootElement().elements("书").get(1);
book.element("作者").setText("hh");

OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("gb2312");

XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"),
format);
writer.write(document);
writer.close();
}
}

2.Demo2.java

package cn.itcast.dom4j;

import java.io.File;
import java.io.FileOutputStream;

import org.dom4j.Document;
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 Demo2 {
/**
* 应用xpath提取xml文档的数据
*
*/
@Test
public void test() throws Exception {
SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/book.xml"));

String value = document.selectSingleNode("//作者").getText();
System.out.println(value);

}
}

3.Demo3.java

package cn.itcast.dom4j;

import java.io.File;

import org.dom4j.Document;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.junit.Test;

public class Demo3 {
/**
* 查找user.xml文档是否有和用户相匹配的用户名和密码
*
*/
@Test
public void test() throws Exception {
String username = "aaa";
String password = "123";

SAXReader reader = new SAXReader();
Document document = reader.read(new File("src/users.xml"));

Node node = document.selectSingleNode("//user[@username='" + username
+ "' and @password='" + password + "']");
if (node == null)
System.out.println("用户名或密码错误！");
else
System.out.println("登录成功！");

}
}