2.1 使用JAXP 对 xml文档进行DOM解析

 //使用 jaxp 对xml文档进行dom解析
 public class Demo2 {

     //必要步骤
     @Test
     public void test() throws Exception {

     //1.创建工厂
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

     //2.得到dom解析器
         DocumentBuilder db = dbf.newDocumentBuilder();

     //3.解析XML文档，得到代表文档的Document
         Document d = db.parse("src/com/xml/javaweb/book.xml");

     }
 }

示例：对xml节点进行增删改查

 public class Demo3 {
     //读取XML文件中：<书名>javaWEB</书名>  节点中的值
     @Test
     public void read() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         NodeList list = d.getElementsByTagName("书名");
         Node node = list.item(1);
         String text = node.getTextContent();
         System.out.println(text);
     }    

     //遍历整个XML文档中的节点
     @Test
     public void read1() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         //得到根节点
         NodeList list = d.getElementsByTagName("书架");
         Node root = list.item(0);
         list(root);
     }

     private void list(Node root) {
         if(root instanceof Element)
         System.out.println(root.getNodeName());

         NodeList nodelist = root.getChildNodes();
         for(int i = 0;i<nodelist.getLength();i++) {
             Node node = nodelist.item(i);
             list(node);
         }
     }

     //拿到 name 属性的值
     @Test
     public void read2() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         Element node = (Element) d.getElementsByTagName("书名").item(0);   //node 里面的方法不够用了  没有指定名字得到属性，在知道得到的是Element的情况下  ，把node强转一下
         String att = node.getAttribute("name");
         System.out.println(att);
     }

     //向XML文档中添加节点          <售价>39.00元</售价>
     @Test
     public void add() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         //创建节点
         Element element = d.createElement("售价");
         element.setTextContent("39.00元");

         //添加节点
         Node node = d.getElementsByTagName("书").item(0);
         node.appendChild(element);

         //更新XML文档
         TransformerFactory tff = TransformerFactory.newInstance();
         Transformer tf = tff.newTransformer();
         tf.transform(new DOMSource(d), new StreamResult(new FileOutputStream("src/com/xml/javaweb/book.xml")));
     }

     //向XML文档中指定位置添加节点          <售价>39.00元</售价>
     @Test
     public void add2() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         //创建节点
         Element element = d.createElement("售价");
         element.setTextContent("29.00元");

         //得到参考节点
         Element ref = (Element) d.getElementsByTagName("售价").item(0);

         //添加节点
         Node node = d.getElementsByTagName("书").item(0);

         //往“书”节点的指定位置插入节点
         node.insertBefore(element, ref);    //在参考节点之前插入新建的节点

         //更新XML文档
         TransformerFactory tff = TransformerFactory.newInstance();
         Transformer tf = tff.newTransformer();
         tf.transform(new DOMSource(d), new StreamResult(new FileOutputStream("src/com/xml/javaweb/book.xml")));
     }

     //向XML文档节点上添加属性         <书名> java就业培训课程</书名> 上添加属性  name = "xxxx"
     @Test
     public void add3() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         //得到要添加属性的节点
         Element element= (Element) d.getElementsByTagName("书名").item(0);
         //往指定节点添加属性
         element.setAttribute("name", "xxxx");

         //更新XML文档
         TransformerFactory tff = TransformerFactory.newInstance();
         Transformer tf = tff.newTransformer();
         tf.transform(new DOMSource(d), new StreamResult(new FileOutputStream("src/com/xml/javaweb/book.xml")));
     }

     //删除XML文档节点          <售价>39.00元</售价>
     @Test
     public void delete() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         //得到要删除的节点
         Element element= (Element) d.getElementsByTagName("售价").item(1);
         //得到要删除的节点的父节点  再调用父节点中删除子节点的方法
         element.getParentNode().removeChild(element);

         //更新XML文档
         TransformerFactory tff = TransformerFactory.newInstance();
         Transformer tf = tff.newTransformer();
         tf.transform(new DOMSource(d), new StreamResult(new FileOutputStream("src/com/xml/javaweb/book.xml")));
     }

     //更新XML文档节点      <作者>张孝祥</作者> -> <作者>xzk</作者>
     @Test
     public void update() throws Exception {
         DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
         DocumentBuilder db = dbf.newDocumentBuilder();
         Document d = db.parse("src/com/xml/javaweb/book.xml");    

         //得到要更新的节点
         Element element= (Element) d.getElementsByTagName("作者").item(1);
         //更新该节点的文本
         element.setTextContent("xzk");

         //更新XML文档
         TransformerFactory tff = TransformerFactory.newInstance();
         Transformer tf = tff.newTransformer();
         tf.transform(new DOMSource(d), new StreamResult(new FileOutputStream("src/com/xml/javaweb/book.xml")));
     }
 }