Dom介绍

JAXP：Java API for XML ProgramingDOM：Document Object MethodDOM特点：(1)将XML文档全部放入内存进行解析，因此耗内存；(2)能够对XML进行增删改查；<person><name>xiazdong</name><age>20</age></person>变成DOM树：二、DOM APIDOM常用的类有：DocumentBuilderFactory、DocumentBuilder、Document、Node、NodeList、Element、Attribute、TransformerFactory、Transformer、DOMSource、StreamResult等类；DOM开发步骤：(1)通过DocumentBuilderFactory获得DocumentBuilder；(2)通过DocumentBuilder解析XML，并获得Document（文档的根节点）;(3)通过Document进行操作；(4)如果对XML进行了改动，则需要TransformerFactory创建一个Transformer；(5)通过Transformer进行保存；常用操作DocumentBuilderFactory类中有：(1)DocumentBuilderFactory factory = DocumentBuilderFactory .newInstance();(2)DocumentBuilder builder = factory.newDocumentBuilder();DocumentBuilder类中有：(1)Document document = builder.parse(new File(""));//解析XML并返回document节点(2)Document document = builder.newDocument();  //创建一个文档Document类中有：(1)NodeList list = getElementsByTagName("name");//获得<name>标签的队列(2)Element e = document.createElement("name");  //创建一个<name>标签，并返回NodeList类中有：(1)Node node = nodeList.item(i); //获得节点队列的第i+1个节点(2)int length = nodeList.getLength(); //获得节点队列的长度Node中有：(1)String text = node.getTextContent(); //获得节点的值(2)node.appendChild(Node child); //向node尾部添加一个child子节点(3)node.insertBefore(Node child,Node beforeNode);//向node的beforeNode子节点之前添加一个child子节点(4)NodeList list = node.getChildNodes();  //获得node全部的子节点(5)Node parent = node.getParentNode(); //获得node的父节点(6)node.removeChild(Node child); //移除node的child子节点(7)node.setTextContent(String text); //设置node 的值(8)String name = node.getNodeName(); //获得标签的名称Element中有：除了Node类的方法，还有(1)element.setAttribute("name","value");  //设置标签的属性(2)String value = element.getAttribute("name");  //获得标签的属性(3)element.removeAttribute("name") //移除标签的属性TranformerFactory 中有：(1)TransformerFactory tfactory = TransformerFactory.newInstance();(2)Transformer tf = tfactory.newTransformer();Transformer中有：(1)tf.transform(Source source,Result result);  //输出DOMSource中有：(1)DOMSource source = new DOMSource(Document document);StreamResult中有：(1)StreamResult result = new StreamResult(new FileOutputStream("1.xml"));三、DOM进行CRUDXML为：<?xml version="1.0" encoding="UTF-8" standalone="no"?><personlist><person><name aaa="xxxx">xiazdong-1</name><age>20</age><salary>1000</salary></person><person><name>xiazdong-2</name><age>21</age><salary>2000</salary></person></personlist>1.Createprivate static void create(DocumentBuilder builder) throws Exception {Document document = builder.newDocument();Element root = document.createElement("person");Element name = document.createElement("name");name.setTextContent("xiazdong");Element age = document.createElement("age");age.setTextContent("20");root.appendChild(name);root.appendChild(age);document.appendChild(root);TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("output.xml")));}private static void insert(Document document)throws Exception {Node person = document.getElementsByTagName("person").item(0);Node name = document.getElementsByTagName("name").item(0);Element tmp = document.createElement("tmpChild");tmp.setTextContent("xxx");person.insertBefore(tmp, name);TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("1.xml")));}2.Readprivate static void read(Document document) {Node node = document.getElementsByTagName("name").item(0);String name = node.getNodeName();String value = node.getTextContent();String attr = ((Element)node).getAttribute("aaa");System.out.println(name);System.out.println(value);System.out.println(attr);}应用：遍历整个XML文档并输出private static void readAll(Document document) {Node root = document.getElementsByTagName("personlist").item(0);read(root);}private static void read(Node node) {if(node instanceof Element)System.out.print("<"+node.getNodeName()+"></"+node.getNodeName()+">");NodeList list = node.getChildNodes();for(int i=0;i<list.getLength();i++){Node n = list.item(i);read(n);}}3.Updateprivate static void update(Document document) throws Exception {Node node = document.getElementsByTagName("name").item(0);node.setTextContent("xiazdong");Element e = (Element)node;e.setAttribute("aaa", "111");TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("1.xml")));}4.Deleteprivate static void delete(Document document) throws Exception{Node name = document.getElementsByTagName("name").item(0);name.getParentNode().removeChild(name);TransformerFactory tfactory = TransformerFactory.newInstance();Transformer tf = tfactory.newTransformer();tf.transform(new DOMSource(document), new StreamResult(new FileOutputStream("1.xml")));}