在java中使用dom4j解析xml

虽然Java中已经有了Dom和Sax这两种标准解析方式

但其操作起来并不轻松，对于我这么一个初学者来说，其中部分代码是活生生的恶心

为此，伟大的第三方开发组开发出了Jdom和Dom4j等工具

鉴于目前的趋势，我们这里来讲讲Dom4j的基本用法，不涉及递归等复杂操作

 

Dom4j的用法很多，官网上的示例有那么点儿晦涩，这里就不写了

首先我们需要出创建一个xml文档，然后才能对其解析

xml文档：

<?xml version="1.0" encoding="UTF-8"?> 
<books> 
   <book id="001"> 
      <title>Harry Potter</title> 
      <author>J K. Rowling</author> 
   </book> 
   <book id="002"> 
      <title>Learning XML</title> 
      <author>Erik T. Ray</author> 
   </book> 
</books> 

 

示例一：用List列表的方式来解析xml

import java.io.File;
import java.util.List;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;



public class Demo {

	public static void main(String[] args) throws Exception {
		SAXReader reader = new SAXReader();
		File file = new File("books.xml");
		Document document = reader.read(file);
		Element root = document.getRootElement();
		List<Element> childElements = root.elements();
		for (Element child : childElements) {
			//未知属性名情况下
			/*List<Attribute> attributeList = child.attributes();
			for (Attribute attr : attributeList) {
				System.out.println(attr.getName() + ": " + attr.getValue());
			}*/
			
			//已知属性名情况下
			System.out.println("id: " + child.attributeValue("id"));
			
			//未知子元素名情况下
			/*List<Element> elementList = child.elements();
			for (Element ele : elementList) {
				System.out.println(ele.getName() + ": " + ele.getText());
			}
			System.out.println();*/
			
			//已知子元素名的情况下
			System.out.println("title" + child.elementText("title"));
			System.out.println("author" + child.elementText("author"));
			//这行是为了格式化美观而存在
			System.out.println();
		}
	}

}

 

示例二：使用Iterator迭代器的方式来解析xml

import java.io.File;
import java.util.Iterator;

import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;



public class Demo {
	public static void main(String[] args) throws Exception {
		SAXReader reader = new SAXReader();
		Document document = reader.read(new File("books.xml"));
		Element root = document.getRootElement();
		
		Iterator it = root.elementIterator();
		while (it.hasNext()) {
			Element element = (Element) it.next();
			
			//未知属性名称情况下
			/*Iterator attrIt = element.attributeIterator();
			while (attrIt.hasNext()) {
				Attribute a  = (Attribute) attrIt.next();
				System.out.println(a.getValue());
			}*/
			
			//已知属性名称情况下
			System.out.println("id: " + element.attributeValue("id"));
			
			//未知元素名情况下
			/*Iterator eleIt = element.elementIterator();
			while (eleIt.hasNext()) {
				Element e = (Element) eleIt.next();
				System.out.println(e.getName() + ": " + e.getText());
			}
			System.out.println();*/
			
			//已知元素名情况下
			System.out.println("title: " + element.elementText("title"));
			System.out.println("author: " + element.elementText("author"));
			System.out.println();
		}
	}
}

 运行结果：

示例三：创建xml文档并输出到文件

import java.io.File;
import java.io.FileOutputStream;

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


public class Demo {
	public static void main(String[] args) throws Exception {
		Document doc = DocumentHelper.createDocument();
		//增加根节点
		Element books = doc.addElement("books");
		//增加子元素
		Element book1 = books.addElement("book");
		Element title1 = book1.addElement("title");
		Element author1 = book1.addElement("author");
		
		Element book2 = books.addElement("book");
		Element title2 = book2.addElement("title");
		Element author2 = book2.addElement("author");
		
		//为子节点添加属性
		book1.addAttribute("id", "001");
		//为元素添加内容
		title1.setText("Harry Potter");
		author1.setText("J K. Rowling");
		
		book2.addAttribute("id", "002");
		title2.setText("Learning XML");
		author2.setText("Erik T. Ray");
		
		//实例化输出格式对象
		OutputFormat format = OutputFormat.createPrettyPrint();
		//设置输出编码
		format.setEncoding("UTF-8");
		//创建需要写入的File对象
		File file = new File("D:" + File.separator + "books.xml");
		//生成XMLWriter对象，构造函数中的参数为需要输出的文件流和格式
		XMLWriter writer = new XMLWriter(new FileOutputStream(file), format);
		//开始写入，write方法中包含上面创建的Document对象
		writer.write(doc);
	}
}

 运行结果：