xml学习笔记

将要读取的xml文档：

<?xml version="1.0" encoding="UTF-8"?>
<书架>
	<书>
		<书名>java开发</书名>
		<作者>andrew</作者>
		<售价>29.00元</售价>
	</书>
	<书>
		<书名>JAva就业培训</书名>
		<作者>andrew</作者>
		<售价>29.00元</售价>
	</书>
</书架>

1.读取xml中节点的值；

public  void readxml() throws Exception{
		//1.创建工厂
		DocumentBuilderFactory factory =  DocumentBuilderFactory.newInstance();
		//2.得到dom解析器
		DocumentBuilder  builder =  factory.newDocumentBuilder();
		//3.解析xml文档，得到代表文档的document
		Document document =  builder.parse("src/book.xml");
		
		//读文档
		NodeList list = document.getElementsByTagName("书名");
		Node nameNode = list.item(1);
		String bookName = nameNode.getTextContent();
		System.out.println(bookName);
		
	}

2.读取xml中所有节点

@Test
	public void readAllNodeName() throws Exception{
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		DocumentBuilder builder = factory.newDocumentBuilder();
		Document document = builder.parse("src/book.xml");
		//得到根节点
		Node rootNode = document.getElementsByTagName("书架").item(0);
		listAllNode(rootNode);
	}

	private void listAllNode(Node rootNode) {
		if(rootNode instanceof Element){
			System.out.println(rootNode.getNodeName());
		}
		
		NodeList  childNodes = rootNode.getChildNodes();
		for(int i=0; i<childNodes.getLength(); i++){
			Node childNode = childNodes.item(i);
			listAllNode(childNode);
			
		}

3.向xml中添加节点

	//向xml文档中添加节点，《售价》44.00元《/售价》
	@Test
	public void add() throws Exception{
		
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		DocumentBuilder builder = factory.newDocumentBuilder();
		Document document = builder.parse("src/book.xml");
		
		//创建节点
		Element price = document.createElement("售价");
		price.setTextContent("44.00元");
		//把节点挂 到第一本书的节点下
		 Element book = (Element) document.getElementsByTagName("书").item(0);
		 book.appendChild(price);
		 
		 //把更新后的内存的数据写回xml中
		 TransformerFactory tfFactory = TransformerFactory.newInstance();
		 Transformer tf = tfFactory.newTransformer();
		 tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
	}