java怎样读写和修改XML文件

xml:

<?xml version="1.0" encoding="UTF-8"?>
<users>
<Messages>
<sendName>sendUsers</sendName>
<receiveName>snake</receiveName>
<date>2007-12-04 12:20:00</date>
<status>0</status>
<message>this is Content</message>
</Messages>

</users>

Java代码：
package com.lianxi.DAO;
import java.io.File;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
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.Node;
import org.w3c.dom.NodeList;
public class UpdateXml {
 public static boolean doc2XmlFile(Document document,String filename)
    {
      boolean flag = true;
      try
       {
            /** 将document中的内容写入文件中   */
             TransformerFactory tFactory = TransformerFactory.newInstance();   
             Transformer transformer = tFactory.newTransformer(); 
            /** 编码 */
            //transformer.setOutputProperty(OutputKeys.ENCODING, "GB2312");
             DOMSource source = new DOMSource(document); 
             StreamResult result = new StreamResult(new File(filename));   
             transformer.transform(source, result); 
         }catch(Exception ex)
         {
             flag = false;
             ex.printStackTrace();
         }
        return flag;      
    }
 
 public static Document load(String filename)
    {
       Document document = null;
      try 
       { 
            DocumentBuilderFactory   factory = DocumentBuilderFactory.newInstance();   
            DocumentBuilder builder=factory.newDocumentBuilder();   
            document=builder.parse(new File(filename));   
            document.normalize();
       }
      catch (Exception ex){
           ex.printStackTrace();
       }  
      return document;
    }
   /**
     *   演示修改文件的具体某个节点的值 
     */
   public static void xmlUpdateDemo()
    {
       Document document = load("c://Message.xml");
       Node root=document.getDocumentElement();
      /** 如果root有子元素 */
      if(root.hasChildNodes())
       {
         /** ftpnodes */
          NodeList ftpnodes = root.getChildNodes();
         /** 循环取得ftp所有节点 */
         for (int i=0;i<ftpnodes.getLength();i++)
          {                      
             NodeList ftplist = ftpnodes.item(i).getChildNodes();
            for (int k=0;k<ftplist.getLength();k++)
             {
               Node subnode = ftplist.item(k);
              /** 删除ftp-chn节点 */
//              if (subnode.getNodeType()==Node.ELEMENT_NODE&&subnode.getNodeName()=="ftp-chn")
//               {
//                  ftpnodes.item(i).removeChild(subnode);
//               }
              /** 修改ftp-host的值为 192.168.0.1 */
              if (subnode.getNodeType()==Node.ELEMENT_NODE&&subnode.getNodeName()=="status")
               {                 
                  subnode.getFirstChild().setNodeValue("1");
               }
             }
            
          }
       }
    
       doc2XmlFile(document,"c://Message.xml");
    }
   public static void main(String args[])throws Exception
   {
    UpdateXml.xmlUpdateDemo();
   }
}