XML之------DOM对XML文档增删改查

用dom对xml文档进行操作实例

可以对xml文档进行增删改查操作

DomDemo1.java

package cn.hncu.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;public class DomDemo1 {@Test //需求:把第一个user节点的name的值取出来    public void getDom() throws Exception {//第一步，通过DocumentBuilderFactory类中的工厂方法等到一个dbf对象DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();//第二步,通过dbf对象创建出一个DocumentBuilder对象DocumentBuilder db = dbf.newDocumentBuilder();//第三步,通过db对象创建出一个Document对象Document dom = db.parse("./xml4/users.xml");// new File("./xml4/users.xml")//System.out.println("dom:"+dom);//然后进行dom操作Node root= dom.getFirstChild();//根节点//System.out.println("root:"+root);System.out.println(root.getNodeName());System.out.println(root.getFirstChild().getNodeName());//上面一句的输出是：#text ----dom中把空白符也看成是一个Node，这种情况对我们的解析通常会造成很大的麻烦//※※为解决上面的问题，我们以后解析时尽量不要用Node，而要用Element。因为Element是元素它不包含属性和文字内容(包括空白符),因此可避开空白符的干扰Element eRoot = (Element)root;NodeList list = eRoot.getElementsByTagName("user");System.out.println("user元素的数量:"+list.getLength());System.out.println("第1个user元素"+list.item(0));//通过item(index)来获取列表中的元素System.out.println("第2个user元素"+list.item(1));Node user1Node = list.item(0);Element eUser1 = (Element)user1Node;//要把Node强转成Element，因为Element是子接口，里面有getElementBy*等方法，而Node没有(只能采用childNodes的方式，这种方式会受空白符的干扰)NodeList listNames = eUser1.getElementsByTagName("name");String nm = listNames.item(0).getNodeName();//name--标签名String nmVal = listNames.item(0).getTextContent();//标签内部所包含的文本内容----innerTextSystem.out.println(nm+","+nmVal);//bug::::直接通过dom对象获取其下节点---经测试,无法通过id来获取Element ee = dom.getElementById("aa");System.out.println("###: "+ee);//null    }@Test //需求:把第二个user节点的age值取出来public void getAge()throws Exception{DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();DocumentBuilder db = dbf.newDocumentBuilder();Document dom = db.parse("./xml4/users.xml");Element root = (Element) dom.getFirstChild();Element user2 =(Element) root.getElementsByTagName("user").item(1);Element eAge =(Element) user2.getElementsByTagName("age").item(0);String age = eAge.getTextContent();System.out.println("age:"+age);}//用Java对xml文档进行CRUD---创建，遍历，更新，删除//遍历@Testpublic void query() throws Exception{DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder db = factory.newDocumentBuilder();Document dom = db.parse( new File("./xml4/users.xml") );Element root = (Element) dom.getFirstChild();NodeList list = root.getElementsByTagName("user");for(int i=0;i<list.getLength();i++){Element user =(Element) list.item(i);String id = user.getAttribute("id");String name = user.getElementsByTagName("name").item(0).getTextContent();String age = user.getElementsByTagName("age").item(0).getTextContent();System.out.println("id:"+id+",name:"+name+",age:"+age);System.out.println("-----------------------");}}//更新---把最后一个user的年龄+10@Testpublic void update() throws Exception{DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder db = factory.newDocumentBuilder();Document dom = db.parse( new File("./xml4/users.xml") );Element root = (Element) dom.getFirstChild();//Element eUser = (Element) root.getLastChild();//注意bug：如果最后一个</user>和</users>标签之前有空白符(包括换行)，那么该句获得的节点是空白符//System.out.println(root.getLastChild().getNodeName());//#textNodeList list =  root.getElementsByTagName("user");Element eUser = (Element) list.item(list.getLength()-1);Element eAge = (Element) eUser.getElementsByTagName("age").item(0);int age = Integer.parseInt(eAge.getTextContent().trim())+10;eAge.setTextContent(""+age);System.out.println(age);//把内存中的当前dom对象存储到xml文件TransformerFactory tf = TransformerFactory.newInstance();Transformer trans = tf.newTransformer();trans.transform(new DOMSource(dom), new StreamResult("./xml4/users.xml"));//把xml源 输出到 目标 ---如果目标存在则是更新，否则是创建}//创建 --需求：添加一个新的user@Testpublic void create() throws Exception{DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder db = factory.newDocumentBuilder();Document dom = db.parse( new File("./xml4/users.xml") );Element root = (Element) dom.getFirstChild();//创建一个新的user元素Element eUserNew = dom.createElement("user");eUserNew.setAttribute("id", "C001");//创建name和age子元素Element eName = dom.createElement("name");eName.setTextContent("李四");Element eAgeNew = dom.createElement("age");eAgeNew.setTextContent("22");//把所创建的元素组装成一棵子树,添加到整棵dom树上eUserNew.appendChild(eName);eUserNew.appendChild(eAgeNew);root.appendChild(eUserNew);//把内存中的当前dom对象存储到xml文件TransformerFactory tf = TransformerFactory.newInstance();Transformer trans = tf.newTransformer();trans.transform(new DOMSource(dom), new StreamResult("./xml4/users.xml"));//把xml源 输出到 目标 ---如果目标存在则是更新，否则是创建}//删除---需求：删除最后一个元素@Testpublic void delete() throws Exception{DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder db = factory.newDocumentBuilder();Document dom = db.parse( new File("./xml4/users.xml") );Element root = (Element) dom.getFirstChild();//获取将要删除的元素NodeList list = root.getElementsByTagName("user");Element e = (Element) list.item( list.getLength()-1 );e.getParentNode().removeChild(e);//把内存中的当前dom对象存储到xml文件TransformerFactory tf = TransformerFactory.newInstance();Transformer trans = tf.newTransformer();trans.transform(new DOMSource(dom), new StreamResult("./xml4/users.xml"));}}

users.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?><users>    <user id="A001">       <name>Jack</name>       <age>25</age>    </user>    <user id="A002">       <name>张三</name>       <age>80</age>    </user>        <user id="C001">    <name>李四</name>    <age>32</age>    </user></users>