解析XML的若干方法

解析XML分为dom和sax两种方式，各有一些不同的java实现

 

一、dom：由W3C定义的接口，将整个XML文档读入内存构建成一个DOM树，再对各个节点进行操作

1）xml解析

@Override
	public void parseXml(String filename){
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
		try{
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document doc = db.parse(filename);
			Element root = doc.getDocumentElement();
			
			NodeList rootNodes = root.getChildNodes();
			System.out.println("root's length="+ rootNodes.getLength());
			iterateNodeList(root,rootNodes);
			
		}catch(Exception e){
			System.out.println(e);
		}
	}

	private void iterateNodeList(Node node, NodeList nodeList){
		System.out.println("=========start:"+node.getNodeName()+"============");
		int nodeListLength = nodeList.getLength();
		for(int i=0;i<nodeListLength;i++){
			Node childNode = nodeList.item(i);
			logNodeInfo(childNode,false);
			
			if(childNode.getNodeType()==Node.ELEMENT_NODE){
				NodeList childNodeList = childNode.getChildNodes();
				iterateNodeList(childNode,childNodeList);
			}
		}
		System.out.println("=========end:"+node.getNodeName()+"============");
	}

原始xml文档如下：

<?xml version="1.0" encoding="UTF-8"?>
<house location="USA">
	<room type="owner">
		<area>
			<value>35</value>
			<unit>m2</unit>
		</area>
	</room>
	<room type="child">
		<area>
			<value>25</value>
			<unit>m2</unit>
		</area>
	</room>
	<room type="guest">
		<area>
			<value>25</value>
			<unit>m2</unit>
		</area>
	</room>
</house>

 从程序parse后的结果可以看到，node之间是有空的文本节点（Node.TEXT_NODE）分隔的，结构如下：

 

 2）xml修改

public void modifyXml(String filename) {
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
		try{
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document doc = db.parse(filename);
			Element root = doc.getDocumentElement();
			
			root.setAttribute("price", "380000$");
			
			TransformerFactory transformerFactory = TransformerFactory.newInstance();
			Transformer transformer = transformerFactory.newTransformer();
			DOMSource domSource = new DOMSource(doc);
			
			File file = new File("./src/house-modify.xml");
			if(file.exists()) file.delete();
			file.createNewFile();
			
			FileOutputStream out = new FileOutputStream(file);
			StreamResult streamResult = new StreamResult(out);
			transformer.transform(domSource, streamResult);
			
			System.out.println("file's absolute path=" + file.getAbsolutePath());
		}catch(Exception  e){
			System.out.println(e);
		}
	}