SpringMvc3+extjs4实现上传与下载功能

<script> 
 Ext.onReady(function() {

  Ext.create('Ext.form.Panel', {
   title : '文件上传',
   width : 400,
   bodyPadding : 10,
   frame : true,
   renderTo : document.body,
   items : [ {
    xtype : 'filefield',
    name : '文件',
    fieldLabel : 'File',
    labelWidth : 50,
    msgTarget : 'side',
    allowBlank : false,
    anchor : '100%',
    buttonText : '请选择文件...'
   } ],

   buttons : [ {
    text : '上传',
    handler : function() {
     var form = this.up('form').getForm();
     if (form.isValid()) {
      form.submit({
       url : '根路径/fileUploadDown/fileUpload',
       waitMsg : '正在上传文件中...',
       success : function(fp, o) {
        Ext.Msg.alert('上传文件成功!');
       }
      });
     }
    }
   } ]
  });

 });
</script>

/**
*记录返回结果*/
 class ExtJSFormResult {

 private boolean success;

 public boolean isSuccess() {
  return success;
 }

 public void setSuccess(boolean success) {

 }

 public String toString() {
  return "{success:" + this.success + "}";
 }
}
 

class FileUploadBean {

  private CommonsMultipartFile file;

  public CommonsMultipartFile getFile() {
   return file;
  }

  public void setFile(CommonsMultipartFile file) {
   this.file = file;
  }
}

/**
 * 文件的上传与下载
 * @author Administrator
 *
 */
@Controller
@RequestMapping(value = "/fileUploadDown")
public class FileUploadAndDownController {
 
 private static int countter=1; //定义一个计数器,用于上传文件的重命名
 
 @Autowired
 private ProAnnexDao<ProAnnex> proAnnextDao;
 
 

 public void setProAnnextDao(ProAnnexDao<ProAnnex> proAnnextDao) {
  this.proAnnextDao = proAnnextDao;
 }

 @RequestMapping(value="fileUpload",method = RequestMethod.POST)
 public @ResponseBody String create(RedirectAttributes redirectAttributes,FileUploadBean uploadItem, 
   BindingResult result,HttpSession session){
  //获取根路径
  String uploadFolderPath = session.getServletContext().getRealPath("/"); 
  ExtJSFormResult extjsFormResult = new ExtJSFormResult();
  try {
   
   if (result.hasErrors()) {
    for (ObjectError error : result.getAllErrors()) {
     System.err.println("Error: " + error.getCode() + " - "
       + error.getDefaultMessage());
    }

    // 设置ExtJS返回 - error
    extjsFormResult.setSuccess(false);

    return extjsFormResult.toString();
   }

   MultipartFile file = uploadItem.getFile();
   String fileName = null;
   InputStream inputStream = null;
   OutputStream outputStream = null;
   if(file.getSize()>0){
     System.out.println("File Size:::" + file.getSize());
    if(file.getSize()>5242880){
      System.out.println("File Size:::" + file.getSize());
      extjsFormResult.setSuccess(false);
     return "error";
    }
    
    inputStream = file.getInputStream();
  
    File newFile = new File(uploadFolderPath + "fileUpload/");
    //如果文件路径不存在就新建一个
    if(!newFile.exists()){
     newFile.mkdirs();
    }
    //获取文件名
    String name=file.getOriginalFilename();
    //从数据库中查询存在此类文件名否
    Long count=proAnnextDao.isRepeatName(name);
    //如果存在一样的文件名,就进行从命名
    if (count>0) {
     name=name.substring(0, name.lastIndexOf("."))+"("+(countter++)+")"+name.substring(name.lastIndexOf("."));
    }
    
    fileName = uploadFolderPath + "fileUpload/" + name;
    outputStream = new FileOutputStream(fileName); 
    int readBytes = 0;
    byte[] buffer = new byte[10000];
    while ((readBytes = inputStream.read(buffer, 0, 10000)) != -1) {
      outputStream.write(buffer, 0, readBytes);
    }
    
    outputStream.close();
    inputStream.close();
    
    
   }

   // 设置ExtJS返回 - sucsess
   extjsFormResult.setSuccess(true);
  } catch (Exception e) {
   
   e.printStackTrace();
   // 设置ExtJS返回 - error
  
   extjsFormResult.setSuccess(false);
  }
  

  return extjsFormResult.toString();
 }
 

}

<!-- 上传文件,限制大小的配置 -->
  <bean id="multipartResolver"
  class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
   <!--resolveLazily属性启用是为了推迟文件解析，以便在Upload中捕获文件大小异常-->
  <property name="resolveLazily" value="true"/>
  <property name="maxUploadSize" value="5242880" />
 </bean>
 
 
 <!-- 将无法mapping到Controller的path交给default servlet handler处理  --> 
 <mvc:default-servlet-handler/><!-- 使用默认的servlet来响应静态文件 -->
 <!-- 文件的上传与下载 -->
 <mvc:view-controller path="/" view-name="redirect:/fileUploadDown"/>

@RequestMapping("/downloadFile") 
 public void download(@Valid @ModelAttribute("downLoadName") String downLoadName,
   HttpServletResponse response,HttpSession session,BindingResult result,HttpServletRequest request) throws IOException { 
  
  response.setCharacterEncoding("UTF-8");
  request.setCharacterEncoding("UTF-8");
  //获取文件的路径
  String url=session.getServletContext().getRealPath("/")+"/fileUpload/"+downLoadName;
  System.out.println(url);
  File file=new File(url);
  
  InputStream input = FileUtils.openInputStream(file); 
  byte[] data = IOUtils.toByteArray(input); 
 
  //System.out.println("文件名:"+downLoadName);
  response.reset(); 
  //设置响应的报头信息(中文问题解决办法)
  response.setHeader("content-disposition","attachment;fileName="+URLEncoder.encode(downLoadName, "UTF-8"));
  response.addHeader("Content-Length", "" + data.length); 
  response.setContentType("application/octet-stream; charset=UTF-8"); 
  
  IOUtils.write(data, response.getOutputStream()); 
  IOUtils.closeQuietly(input); 
  
 }