java下载文件

@GetMapping(value = "/file")
      public HttpServletResponse download(String filename, HttpServletResponse response)throws IOException {

     System.out.println("--------getFilePath-----"+myattr.getFilepath()+filename);
     filename = "1.jpg";
     if (filename.equals("")) {
            return null;
    }
     System.out.println("--------filename-----"+filename);
     
          File file = new File(myattr.getFilepath()+filename);
          if (!file.exists()) {
            return null;
     }
          System.out.println("---exists-----filename-----"+filename);
          if(file.exists()){
              FileInputStream is = new FileInputStream(file);
              int i = is.available(); // 得到文件大小
              byte data[] = new byte[i];
              is.read(data); // 读数据
              is.close();
              response.setContentType("image/jpg"); // 设置返回的文件类型
              OutputStream toClient = response.getOutputStream(); // 得到向客户端输出二进制数据的对象
              toClient.write(data); // 输出数据
              toClient.flush();
              toClient.close();
              return null;  
          }
          return response;
      }