java Struts2实现文件上传下载

 <form id="form" action="Upload!uploads.action" method="post" enctype="multipart/form-data">  
       <input type="file" name="file" /> 
       <input type="button" onclick="tijiao()" value="提交">
       </form>  

           private File file;//用此属性接收页面表单的file值
	   private String fileFileName;//此处的文件名必须是表单file name+FileName
	   private String types;    
	   private IfileService service;
	   private String commonTypes;
		                @Override
  		  	        public String execute() throws Exception {
				String path=ServletActionContext.getRequest().getRealPath("/upload");
				 File fi= new File(path);
				if(!fi.exists())
					   fi.mkdir();
				FileOutputStream os=new FileOutputStream(path+"/"+fileFileName);
				byte buffer[]=FileToByte.getBytesFromFile(file);
			      os.write(buffer);
			      os.close();
			      
				return "success";
			}

 public InputStream getInputStream() {
    	InputStream stream=ServletActionContext.getServletContext().getResourceAsStream(
			    "/upload/" + fileName);
       return	stream;
	}
@Override
	public String execute() throws Exception {
		if(getInputStream()==null)
		{
			return INPUT;
		}else
		{
			 return updateFileDownLoadCount();
		}
	}

		             2048
		             application/octet-stream;charset=ISO8859-1
		             attachment;fileName="${fileName}"