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：
(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 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")));
}