xml文档，dom树的增删改查

package cn.hncu.jaxp.dom;

import java.io.File;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.dom.DOMSource;

import javax.xml.transform.stream.StreamResult;

import org.junit.Test;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

/*

 * dom树模型中的增删改查

 * 

 * 

 * 以后要遍历文档，最好的选择方式是: 采用Element中的getElementsByTagName(String name),

 * 返回类型为:NodeList, 获取当前元素下面的所有对应标签的那些子元素( 仅仅是标签节点---能够去除文本内容尤其是空白符的干扰)。

 * 建议不要采用如下两种方式: 1)通过Node中的 getChildNodes(),返回类型为:NodeList, 获取当前节点的所有

 * 子节点(包括文本内容和标签节点)----不选择的理由:文本内容尤其是空白符也是其中的孩子节点，会产生干扰

 * 2)通过Document的getElementById(String elementId), 返回Element节点，

 * 这种方式在browse-dom中用起来是非常方便的，但在Java-dom中必须得给

 * DocumentBuilderFactory对象设置schema

 *

 */

public class Domdemo2 {
@Test
// 查
public void iteratorDemo() throws Exception {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document dom = db.parse("./xml/users.xml");

Element root = (Element) dom.getFirstChild();
NodeList userlist = root.getElementsByTagName("user");

for (int i = 0; i < userlist.getLength(); i++) {
Element nodeuser = (Element) userlist.item(i);
String id = nodeuser.getAttribute("id");
String name = nodeuser.getElementsByTagName("name").item(0)
.getTextContent();
String age = nodeuser.getElementsByTagName("age").item(0)
.getTextContent();
System.out.println("id:" + id + ", name:" + name + ", age:" + age);
}
}

// 增
@Test
public void adddemo() throws Exception {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document dom = db.parse(new File("./xml/users.xml"));

// 创建一个新的user元素
Element user = dom.createElement("user");
// 给当前user元素添加id属性
user.setAttribute("id", "C001");
// 为新的user元素创建子节点
Element eName = dom.createElement("name");
eName.setTextContent("张飞");
Element eage = dom.createElement("age");
eage.setTextContent("22");

// 组装eUser子树
user.appendChild(eName);
user.appendChild(eage);

// 把 eUser子树 添加到 dom树 ----注意,要让根节点(dom的第一个孩子)去添加
dom.getFirstChild().appendChild(user);

// 前面操作的都是内存中的dom对象，要永久有效，必须把该dom对象"转换"到永久设备中
TransformerFactory tff = TransformerFactory.newInstance();
Transformer tf = tff.newTransformer();
tf.transform(new DOMSource(dom), new StreamResult("./xml/users.xml"));
}

// 删--把文档中的最后一个<user>节点删除
@Test
public void deldemo() throws Exception {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document dom = db.parse(new File("./xml/users.xml"));

// 获取最后一个user节点
Element root = (Element) dom.getFirstChild();
NodeList userlist = root.getElementsByTagName("user");
Element usernode = (Element) userlist.item(userlist.getLength() - 1);

// 删掉该user节点
usernode.getParentNode().removeChild(usernode);
// 前面操作的都是内存中的dom对象，要永久有效，必须把该dom对象"转换"到永久设备中
TransformerFactory tff = TransformerFactory.newInstance();
Transformer tf = tff.newTransformer();
tf.transform(new DOMSource(dom), new StreamResult("./xml/users.xml"));
}

// 改--需求:把最后一个user的年龄改为 age+10
@Test
public void updateDemo() throws Exception{
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document dom = db.parse(new File("./xml/users.xml"));

Element root = (Element) dom.getFirstChild();
NodeList nodeList = root.getElementsByTagName("user");
Element euser = (Element) nodeList.item( nodeList.getLength()-1 );
Node nodeage = euser.getElementsByTagName("age").item(0);
nodeage.setTextContent( Integer.parseInt(nodeage.getTextContent()) +10 +"" );

TransformerFactory tff = TransformerFactory.newInstance();
Transformer tf = tff.newTransformer();
tf.transform(new DOMSource(dom), new StreamResult("./xml/users.xml"));
}
}

users文档

<?xml version="1.0" encoding="UTF-8" standalone="no"?><users>
<user id="A001">
<name>Jack</name>
<age>22</age>
</user>
<user id="A002">
<name>张三</name>
<age>24</age>
</user>
<user id="B001">
<name>小李</name>
<age>20</age>
</user>
<user id="B002">
<name>小张</name>
<age>28</age>
</user>
<user id="C001">
<name>刘备</name>
<age>45</age>
</user>

</users>