DOM4J

DOM4J:开源,支持XML,XPath,XSLT。与JDOM一样应用与JAVA平台。它的API完全支持DOM,SAX,JAXP。http://www.dom4j.org

Dom4j是早期由开发JDOM的人分离出来独立开发的。与JDOM不同的是:Dom4j使用接口和抽象基类,虽然dom4j的API相对复杂一些,但比JDOM更灵活性。SUN的JAXM跟HIBERNATE都是使用DOM4J

Dom4j也使用SAX解析器来分析XML文档,创建DOM4J树。此外,dom4j也接收DOM格式的内容,并提供从dom4j树到SAX事件流或W3C DOM树中的输出机制。

与JDOM不同的是:DOM4J自带了一个SAX解析器Aelfred2,如果没有显示设置,那么默认会加载JAXP配置的解析器,如果创建解析器失败,那么最后将使用dom4j自带的Aelfred2解析器。

DOM4J实例一:DOM4j的API使用
Dom4jTest.java

import java.io.IOException;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

public class Dom4jTest {

	
	public static void main(String[] args) {
		//1.创建DOC对象
		Document doc = DocumentHelper.createDocument();
		//2.创建处理指令
		doc.addProcessingInstruction("xml-stylesheet", "type='text/xsl' href='students.xsl'");
		//3.创建根元素
		Element root = DocumentHelper.createElement("students");
		doc.setRootElement(root);
		//4.创建子元素
		Element eltStu = root.addElement("student");
		Element eltName = eltStu.addElement("name");
		Element eltAge = eltStu.addElement("age");
		//5.设置文本节点值
		eltName.setText("张三");
		eltAge.setText("23");
		//6.输出
		//PrintWriter pw = new PrintWriter(System.out);
		OutputFormat outFmt = new OutputFormat("      ",true);
		outFmt.setEncoding("gb2312");
		try {
			//doc.write(pw);
			//pw.close();
			XMLWriter xmlWriter = new XMLWriter(outFmt);
			xmlWriter.write(doc);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

DOM4J实例二:遍历整个XML文档树
VisitorTest.java

import java.io.File;
import org.dom4j.*;
import org.dom4j.io.SAXReader;

public class VisitorTest{

	public static void main(String[] args){
		SAXReader saxReader=new SAXReader();
		try{
			Document doc=saxReader.read(new File("students.xml"));
			doc.accept(new MyVisitor());
		}catch (DocumentException e){
			e.printStackTrace();
		}
	}
	
	private static class MyVisitor extends VisitorSupport{
		public void visit(Attribute node){
			System.out.println("Attribute: "+node.getName()+"="+node.getValue());
		}

		public void visit(Element node){
			if(node.isTextOnly()){
				System.out.println("Element: "+node.getName()+" "+node.getText());
			}else{
				System.out.println("------------"+node.getName()+"-------------");
			}
		}

		public void visit(ProcessingInstruction node){
			System.out.println("PI: "+node.getTarget()+" "+node.getText());
		}
		
	}
}

DOM4J实例三:基于事件的处理(对内容多的XML进行处理)
ElementHandlerTest.java

import java.io.File;
import org.dom4j.*;
import org.dom4j.io.SAXReader;

public class ElementHandlerTest{

	
	public static void main(String[] args){
		SAXReader saxReader=new SAXReader();
		saxReader.addHandler("/students/student",new StudentHandler());
		try{
			saxReader.read(new File("students.xml"));
		}catch (DocumentException e){
			e.printStackTrace();
		}
	}
	
	private static class StudentHandler implements ElementHandler{
		public void onStart(ElementPath path){
			Element elt=path.getCurrent();
			System.out.println("Found student: "+elt.attributeValue("sn"));
			path.addHandler("name",new NameHandler());
		}

		public void onEnd(ElementPath path){
			path.removeHandler("name");		
		}
	}

	private static class NameHandler implements ElementHandler{
		public void onStart(ElementPath path){
			System.out.println(path.getPath());
		}

		public void onEnd(ElementPath path){
			Element elt=path.getCurrent();
			System.out.println(elt.getName()+": "+elt.getText());
		}
	}
}