JAXP之DOM总结

一、JAXP、DOM介绍

JAXP：Java API for XML Programing

DOM：Document Object Method

DOM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 API

DOM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CRUD

XML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.Create

private 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.Read

private 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.Update

private 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.Delete

private 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")));
}