jaxp对xml文档进行dom解析并进行CRUD操作

下面是要解析的xml文档里面的内容：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<person>
	<student>
		<name length="4">jack</name>
		<age>45</age>
		<sex>man</sex>
	</student>

	<student>
		<name>bill</name>
		<age>21</age>
		<sex>women</sex>
	</student>
</person>

下面我们来用jaxp来对这个文档进行dom解析：

public class JAXPDomParse {
	private static DocumentBuilderFactory factory;
	private static DocumentBuilder builder;
	private static Document doc;
	
	@BeforeClass
	public static void init() {
		try {
			factory = DocumentBuilderFactory.newInstance();
			builder =factory.newDocumentBuilder();
			//解析xml文档，获取文档对象，将其加载到内存中
			doc = builder.parse("src/student.xml");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 读取xml文档中<name>bill</name>中的值
	 * @throws Exception
	 */
	@Test
	public void readXML1() throws Exception {
		NodeList list = doc.getElementsByTagName("name");
		Node node = list.item(1);
		String value = node.getTextContent();
		System.out.println(value);
	}
	
	/**
	 * 读取xml文档中所包含的所有节点,除了文本节点以外
	 * @throws Exception
	 */
	@Test
	public void readXML2() throws Exception {
		NodeList nodes = doc.getElementsByTagName("person");
		Node rootNode = nodes.item(0);
		printChild(rootNode);
	}
	
	/**
	 * 读取xml文档中<name length="4">jack</name>的length的属性值
	 * @throws Exception
	 */
	@Test
	public void readXML3() throws Exception {
		NodeList nodes = doc.getElementsByTagName("name");
		/*
		 * Node nameNode = nodes.item(0);
		 * 由于Node对象给我们提供获取属性的方法得到的是一个数组，很不方便，
		 * 所以我们将Node对象转换成Element对象，从而使获得属性值变得
		 * 很方便
		 */
		Element nameNode = (Element) nodes.item(0);
		String value = nameNode.getAttribute("length");
		System.out.println(Integer.parseInt(value));
	}
	
	/**
	 * 向第一个student节点里面的name与age之间插入一个节点<weight no="xxxx">120</weight>
	 * @throws Exception
	 */
	@Test
	public void addXML() throws Exception {
		NodeList list = doc.getElementsByTagName("student");
		Node node = list.item(0);
		Element weight = doc.createElement("weight");
		weight.setAttribute("no", "xxxx");
		weight.setTextContent("120");
		
		//获取参考节点
		Node ageNode = doc.getElementsByTagName("age").item(0);
		/*
		 * 如果把节点直接插入到末尾就不用这么麻烦了，
		 * 直接用Node对象的appendChild()就
		 * ok了。
		 */
		node.insertBefore(weight, ageNode);
		updateXMLData();
	}
	
	/**
	 * 删除第一个student节点内的sex节点
	 */
	@Test
	public void deleteXML() throws Exception {
		Node sexNode = doc.getElementsByTagName("sex").item(0);
		sexNode.getParentNode().removeChild(sexNode);
		updateXMLData();
	}
	
	/**
	 * 更新第一个student节点内的sex节点的值
	 */
	@Test
	public void updateXML() throws Exception {
		Node sexNode = doc.getElementsByTagName("sex").item(0);
		sexNode.setTextContent("women");
		updateXMLData();
	}
	
	/**
	 * 把更新在内存里的数据写回到xml文档里
	 */
	private void updateXMLData() throws Exception {
		Transformer transformer = TransformerFactory.newInstance().newTransformer();
		transformer.transform(new DOMSource(doc), new StreamResult(new FileOutputStream("src/student.xml")));
	}

	/**
	 * 通过递归的方法打印出根节点的所有子节点
	 */
	private void printChild(Node node) {
		if(node.getNodeType() == 1) {
			System.out.println(node.getNodeName());
		}
		NodeList list = node.getChildNodes();
		
		for(int i = 0;i < list.getLength();i++) {
			printChild(list.item(i));
		}
	}
}