用spring controller显示图形

用spring controller显示图形
 public ModelAndView getPicture(HttpServletRequest request,
   HttpServletResponse response) {
  String processDefinitionId = request
    .getParameter("processDefinitionId");
  byte[] bytes = adminServices.getProcessImageBytes(processDefinitionId); //获得图片的Byte[]
  OutputStream out = null;
  try {
   out = response.getOutputStream();
   out.write(bytes);   //打印图片
   out.flush();
  } catch (IOException ex) {
  }
  return null;
 }