@RequestMapping(method = {RequestMethod.POST})
    public ResultEntity form1(@RequestBody String requestBody) throws UnsupportedEncodingException {
  logger.info("================ request body ================");\
  logger.info("request body is : {}", requestBody);
 }

$.ajax({
    url:'http://localhost/api/spd',
    data: JSON.stringify({name:'zhangsan', age: 18}),
    type:'POST',
    contentType: 'application/json',
    success:function(result){
        console.log(result);
    },
    error:function(error){
     console.log(error);
    }
});

$.ajax({
    url:'http://localhost/api/spd',
    data: 'this is a message',
    type:'POST',
    contentType: 'text/plain',
    success:function(result){
        console.log(result);
    },
    error:function(error){
     console.log(error);
    }
});

 protected String getRequestBody(HttpServletRequest request) {
  try {
   BufferedReader reader = request.getReader();
   char[] buf = new char[512];
   int len = 0;
   StringBuffer contentBuffer = new StringBuffer();
   while ((len = reader.read(buf)) != -1) {
    contentBuffer.append(buf, 0, len);
   }
   return contentBuffer.toString();
  } catch (IOException e) {
   e.printStackTrace();
  }  
  return "null";
 }