Dom解析XML

DOM是把XML整个文件都载入到内存，生成一个树，然后通过遍历来获取需要的标签及对应的值。
对于需要遍历所有节点的话，这样做速度会比较快，一次载入就可以了。
如果是只关心其中的某个节点，那这样的效率是很低的。

接下代码如下：

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import com.zhouxf.javabase.xml.XmlDocument;

 
public class DomXmlDocument implements XmlDocument {
	private Document document;

	public void init() {
		try {
			DocumentBuilderFactory factory = DocumentBuilderFactory
					.newInstance();
			DocumentBuilder builder = factory.newDocumentBuilder();
			this.document = builder.newDocument();
		} catch (ParserConfigurationException e) {
			System.out.println(e.getMessage());
		}
	}

	public void createXml(String fileName) {
		// 创建根目标标签
		Element root = this.document.createElement("users");
		this.document.appendChild(root);
		// 创建子标签
		Element employee = this.document.createElement("user");
		Element name = this.document.createElement("name");
		name.appendChild(this.document.createTextNode("zhouxf"));
		employee.appendChild(name);
		Element age = this.document.createElement("age");
		age.appendChild(this.document.createTextNode("29"));
		employee.appendChild(age);
		root.appendChild(employee);
		// 创建转换源数据为树数据的工具的工厂
		TransformerFactory tf = TransformerFactory.newInstance();
		try {
			// 获取一个转化工具
			Transformer transformer = tf.newTransformer();
			DOMSource source = new DOMSource(document);
			transformer.setOutputProperty(OutputKeys.ENCODING, "utf-8");
			// 是否允许空格
			transformer.setOutputProperty(OutputKeys.INDENT, "yes");
			// 输出文件
			PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));
			StreamResult result = new StreamResult(pw);
			// 转换输出结果
			transformer.transform(source, result);
			System.out.println("生成XML文件成功!");
		} catch (TransformerConfigurationException e) {
			System.out.println(e.getMessage());
		} catch (IllegalArgumentException e) {
			System.out.println(e.getMessage());
		} catch (FileNotFoundException e) {
			System.out.println(e.getMessage());
		} catch (TransformerException e) {
			System.out.println(e.getMessage());
		}
	}

	public void parserXml(String fileName) {
		try {
			// 创建build 工厂
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			// 通过工厂创建一个builder
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document document = db.parse(fileName);
			Element documentElement = document.getDocumentElement();
			NodeList users = documentElement.getChildNodes();
			// NodeList users = document.getChildNodes();
			for (int i = 0; i < users.getLength(); i++) {
				Node user = users.item(i);
				NodeList userInfo = user.getChildNodes();
				for (int j = 0; j < userInfo.getLength(); j++) {
					Node node = userInfo.item(j);
					NodeList userMeta = node.getChildNodes();
					for (int k = 0; k < userMeta.getLength(); k++) {
						System.out.println(userMeta.item(k).getNodeName() + ":"
								+ userMeta.item(k).getTextContent());
					}
				}
			}
			System.out.println("解析完毕");
		} catch (FileNotFoundException e) {
			System.out.println(e.getMessage());
		} catch (ParserConfigurationException e) {
			System.out.println(e.getMessage());
		} catch (SAXException e) {
			System.out.println(e.getMessage());
		} catch (IOException e) {
			System.out.println(e.getMessage());
		}
	}
}

public class DomTest {

	public static void main(String[] args) {
		DomXmlDocument document = new DomXmlDocument();
		URL resource = DomTest.class.getClassLoader().getResource(
				"./xml/test.xml");
		try {
			if (resource != null) {
				System.out.println(resource.toURI().getPath());
				document.parserXml(resource.toURI().getPath());
			} else {
				System.out.println("null..........");
			}
		} catch (URISyntaxException e) {
			e.printStackTrace();
		}

	}
}

xml很简单：

<?xml version="1.0" encoding="UTF-8"?>
<users>
	<user>
		<name>
			zhouxf
     </name>
		<age>
			28
     </age>
	</user>
</users>