ExtJS部分的代码如下：

Ext.onReady(function(){    
   
 var loadform = new Ext.form.FormPanel({    
     renderTo:'file',   
     labelAlign: 'right',    
     title: '文件上传',    
     labelWidth: 60,    
     frame:true,   
     url: './upload.do?cmd=uploadFiles',//fileUploadServlet    
     width: 300,    
     height:200,   
     fileUpload: true,   
     items: [{    
        xtype: 'textfield',   
        id:'files',
        fieldLabel: '文件名',    
        name: 'files',    
        inputType: 'file'//文件类型    
      }],           
    buttons: [{    
       text: '上传',    
       handler: function() {   
     loadform.getForm().submit({ 
      method:'POST',
         success: function(loadform,action){    
            Ext.Msg.alert('信息', action.result.info);    
         },    
         failure: function(){    
          Ext.Msg.alert('错误',action.result.info);    
        }   
     });   
   }    
  }]    
  });    
  
 }); 

Action部份的代码如下：

public static final  String UPLOAD_FILE_PATH = "F:\\p_w_picpath\\"; // 文件上传后，保存的位置

/**
  * 实现文件上传
  * @param mapping
  * @param form
  * @param request
  * @param response
  * @return
  * @throws Exception
  */
 public ActionForward executeUploadFiles(ActionMapping mapping,
   ActionForm form, HttpServletRequest request,
   HttpServletResponse response) throws Exception {
  PrintWriter out = response.getWriter();   
  DictInfoForm dictInfoForm=(DictInfoForm)form; 
  System.out.println(dictInfoForm.getFiles().getFileName());
  FormFile uploadFile = dictInfoForm.getFiles();
         //得到文件名
         String fileName = uploadFile.getFileName();
         //得到文件大小
         int fileSize = uploadFile.getFileSize();
         System.out.println("FileName = " + fileName);
         System.out.println("FileSize=" + fileSize);
         boolean result = true;
         try{
             //得到文件的输入流
             InputStream is = uploadFile.getInputStream();
             //上传文件
             uploadFile(fileName,is);
         }catch(IOException ex){
             ex.printStackTrace();
             //假如上传文件失败，设置一个失败的标记位
             result = false;
         }
         
         if(result){
          out.write("{success:true,info:'方件上传成功'}");
         } else {
          out.write("{success:false,info:'方件上传成功'}");
         } 
        
         return mapping.findForward("");
 }
  /**
     * 上传文件
     * @param fileName
     * @param is
     * @throws IOException
     */
    private void uploadFile(String fileName,InputStream is) throws IOException{
        OutputStream os = new FileOutputStream(UPLOAD_FILE_PATH + fileName);
        //8k缓存数据
        byte[] buffer = new byte[1024 * 8];
        //设置读进缓存的字节数
        int len;
        while((len=is.read(buffer))!=-1){
            //将缓存数据写入磁盘
            os.write(buffer,0,len);
        }
        //关闭输出流
        os.close();
        //关闭输入流
        is.close();
    }