java dom操作xml

转载http://blog.chinaunix.net/u/20045/showart_334646.html
我们需要引入的包：

import java.io.*;
import javax.xml.transform.*;   
import javax.xml.transform.dom.DOMSource;   
import javax.xml.transform.stream.StreamResult;       
import javax.xml.parsers.*;   
import org.w3c.dom.*;
import org.xml.sax.InputSource;
1、将XML文件的内容转化为String

   /**
     * doc2String
     * 将xml文档内容转为String
     * @return 字符串
     * @param document
     */
   public static String doc2String(Document document)
    {
      String s = "";
      try
       {
           TransformerFactory tFactory = TransformerFactory.newInstance();   
           Transformer transformer = tFactory.newTransformer();
          /** 使用GB2312编码 */
          //transformer.setOutputProperty(OutputKeys.ENCODING, "GB2312");
           Source source = new DOMSource( document );            
          /** 直接输出到控制台 */
          //Result output = new StreamResult( System.out );         
           StringWriter out = new StringWriter(); 
           Result output = new StreamResult( out );
           transformer.transform( source, output );
           out.flush();
           s = out.toString();
       }catch(Exception ex)
       {            
           ex.printStackTrace();
       }      
      return s;
    }
2、将符合XML格式的String 转化为XML Document

   /**
     * string2Document
     * 将字符串转为Document
     * @return 
     * @param s xml格式的字符串
     */
   public static Document string2Document(String s)
    {
       Document document = null;
      try
       {
           DocumentBuilder parser = DocumentBuilderFactory.newInstance().newDocumentBuilder();
           document = parser.parse( new InputSource(new StringReader(s)) );
       }catch(Exception ex)
       {            
            ex.printStackTrace();
       }
      return document;
    }
3、将Document对象保存为一个xml文件到本地

   /**
     * doc2XmlFile
     * 将Document对象保存为一个xml文件到本地
     * @return true:保存成功   flase:失败
     * @param filename 保存的文件名
     * @param document 需要保存的document对象
     */
   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;      
    }
4、将xml格式的字符串保存为本地文件，如果字符串格式不符合xml规则，则返回失败

   /**
     * string2XmlFile
     * 将xml格式的字符串保存为本地文件，如果字符串格式不符合xml规则，则返回失败
     * @return true:保存成功   flase:失败
     * @param filename 保存的文件名
     * @param str 需要保存的字符串
     */
   public static boolean string2XmlFile(String str,String filename)
    {
      boolean flag = true;
      /* 以下格式生成的文件是以UTF-8为格式 */
      try
       {
          Document doc = string2Document(str);       
          flag = doc2XmlFile(doc,filename);
       }catch (Exception ex)
       {
          flag = false;
          ex.printStackTrace();
       }
      /** 以下不通过xml格式验证，象生成普通文件格式的方法生成xml文件
         OutputStream os = null;       
         try {
                 os = new FileOutputStream(filename);
                 os.write(str.getBytes());
                 os.flush();
         } catch (Exception ex) {
                 flag = false;
                 ex.printStackTrace();
         }finally
         {     
               try{ 
                 if (os!=null) os.close();
               }catch (Exception ex) {
                 ex.printStackTrace();
               }              
         }
          */
      return flag;
    }
5、载入一个xml文档

   /**
     * load
     * 载入一个xml文档
     * @return 成功返回Document对象，失败返回null
     * @param uri 文件路径
     */
   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;
    }
6、演示String保存为xml文件

   /**
     * xmlWriteDemoByString
     * 演示String保存为xml文件
     */
   public void xmlWriteDemoByString()
    {
      String s = "";
      /** xml格式标题 "<?xml version='1.0' encoding='GB2312'?>" 可以不用写*/
       s = "<?xml version='1.0' encoding='GB2312'?>"
          +"<config>\r\n"
          +"    <ftp name='DongDian'>\r\n"
          +"      <ftp-host>127.0.0.1</ftp-host>\r\n"
          +"      <ftp-port>21</ftp-port>\r\n"
          +"      <ftp-user>cxl</ftp-user>\r\n"
          +"      <ftp-pwd>longshine</ftp-pwd>\r\n"
          +"      <!-- ftp最多尝试连接次数 -->\r\n"
          +"      <ftp-try>50</ftp-try>\r\n"
          +"      <!-- ftp尝试连接延迟时间 -->\r\n"
          +"      <ftp-delay>10</ftp-delay>\r\n"
          +"      <ftp-chn>中文</ftp-chn>\r\n"
          +"   </ftp>\r\n"
          +"</config>\r\n";
      //将文件生成到classes文件夹所在的目录里   
       string2XmlFile(s,"xmlWriteDemoByString.xml");   
      //将文件生成到classes文件夹里   
       string2XmlFile(s,"classes/xmlWriteDemoByString.xml");  
    }
7、演示手动创建一个Document，并保存为XML文件

   /**
     * 演示手动创建一个Document，并保存为XML文件
     */
   public void xmlWriteDemoByDocument()
    {
        /** 建立document对象 */
        try 
         { 
            DocumentBuilderFactory   factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();

            Document document = builder.newDocument();
           /** 建立config根节点 */
            Element configElement = document.createElement("config");
            document.appendChild( configElement );
           /** 建立ftp节点 */
            Comment cmt = document.createComment("东电ftp配置");        
            configElement.appendChild(cmt);        
       
            Element ftpElement = document.createElement("ftp");
            configElement.appendChild(ftpElement);
            ftpElement.setAttribute("name","DongDian");
           /** ftp 属性配置 */
            Element element = document.createElement("ftp-host");
            element.appendChild(document.createTextNode( "127.0.0.1" ));
            ftpElement.appendChild(element);
           
            element = document.createElement("ftp-port");
            element.appendChild(document.createTextNode( "21" ));
            ftpElement.appendChild(element);
           
            element = document.createElement("ftp-user");
            element.appendChild(document.createTextNode( "cxl" ));
            ftpElement.appendChild(element);
           
            element = document.createElement("ftp-pwd");
            element.appendChild(document.createTextNode( "longshine" ));
            ftpElement.appendChild(element);
           
            element = document.createElement("ftp-try");
            element.appendChild(document.createTextNode( "50" ));
            ftpElement.appendChild(element);
           
            element = document.createElement("ftp-chn");
            element.appendChild(document.createTextNode( "中文" ));
            ftpElement.appendChild(element);
           
           /** 保存Document */
            doc2XmlFile(document,"classes/xmlWriteDemoByDocument.xml");
       }
      catch (Exception ex){
           ex.printStackTrace();
       }       
    }
8、演示读取文件的具体某个节点的值

   /**
     *   演示读取文件的具体某个节点的值 
     */
   public static void xmlReadDemo()
    {
       Document document = load("classes/xmlWriteDemoByDocument.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);
              if (subnode.getNodeType()==Node.ELEMENT_NODE)
               {
                /** 打印ftp所有节点属性的值 */
                 System.out.println(subnode.getNodeName()+":"+subnode.getFirstChild().getNodeValue());
               }
             }
          }
       }
    }
9、演示修改文件的具体某个节点的值

   /**
     *   演示修改文件的具体某个节点的值 
     */
   public static void xmlUpdateDemo()
    {
       Document document = load("classes/xmlWriteDemoByDocument.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()=="ftp-host")
               {                 
                  subnode.getFirstChild().setNodeValue("192.168.0.1");
               }
             }
            
          }
       }
      /** 修改完后重新保存 */
       doc2XmlFile(document,"classes/xmlWriteDemoByDocument.xml");
    }