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雖然Java中已經有了Dom和Sax這兩種標準解析方式

但其操作起來并不輕松，對于我這么一個初學者來說，其中部分代碼是活生生的惡心

為此，偉大的第三方開發組開發出了Jdom和Dom4j等工具

鑒于目前的趨勢，我們這里來講講Dom4j的基本用法，不涉及遞歸等復雜操作

Dom4j的用法很多，官網上的示例有那么點兒晦澀，這里就不寫了

首先我們需要出創建一個xml文檔，然后才能對其解析

xml文檔：

復制代碼代碼如下:

	
	<?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列表的方式來解析xml

復制代碼代碼如下:

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) {
   //未知屬性名情況下
   /*List<Attribute> attributeList = child.attributes();
   for (Attribute attr : attributeList) {
    System.out.println(attr.getName() + ": " + attr.getValue());
   }*/

   //已知屬性名情況下
   System.out.println("id: " + child.attributeValue("id"));

   //未知子元素名情況下
   /*List<Element> elementList = child.elements();
   for (Element ele : elementList) {
    System.out.println(ele.getName() + ": " + ele.getText());
   }
   System.out.println();*/

   //已知子元素名的情況下
   System.out.println("title" + child.elementText("title"));
   System.out.println("author" + child.elementText("author"));
   //這行是為了格式化美觀而存在
   System.out.println();
  }
}

}

示例二：使用Iterator迭代器的方式來解析xml

復制代碼代碼如下:

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();

   //未知屬性名稱情況下
   /*Iterator attrIt = element.attributeIterator();
   while (attrIt.hasNext()) {
    Attribute a = (Attribute) attrIt.next();
    System.out.println(a.getValue());
   }*/

   //已知屬性名稱情況下
   System.out.println("id: " + element.attributeValue("id"));

   //未知元素名情況下
   /*Iterator eleIt = element.elementIterator();
   while (eleIt.hasNext()) {
    Element e = (Element) eleIt.next();
    System.out.println(e.getName() + ": " + e.getText());
   }
   System.out.println();*/

   //已知元素名情況下
   System.out.println("title: " + element.elementText("title"));
   System.out.println("author: " + element.elementText("author"));
   System.out.println();
  }
}
}

運行結果：

示例三：創建xml文檔并輸出到文件

復制代碼代碼如下:

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();
  //增加根節點
  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");

  //為子節點添加屬性
  book1.addAttribute("id", "001");
  //為元素添加內容
  title1.setText("Harry Potter");
  author1.setText("J K. Rowling");

  book2.addAttribute("id", "002");
  title2.setText("Learning XML");
  author2.setText("Erik T. Ray");

  //實例化輸出格式對象
  OutputFormat format = OutputFormat.createPrettyPrint();
  //設置輸出編碼
  format.setEncoding("UTF-8");
  //創建需要寫入的File對象
  File file = new File("D:" + File.separator + "books.xml");
  //生成XMLWriter對象，構造函數中的參數為需要輸出的文件流和格式
  XMLWriter writer = new XMLWriter(new FileOutputStream(file), format);
  //開始寫入，write方法中包含上面創建的Document對象
  writer.write(doc);
}
}