Read the correct way to use @RequestBody

This paper mainly studies the proper use of @RequestBody, as follows.

Recently, I was accepting the work of a colleague who was going to leave, and the project I took over was built with SpringBoot. I saw the following writing:

@RequestMapping("doThis") 
public String doThis(HttpServletRequest request, 
    @RequestParam("id") Long id, //  The user ID 
    @RequestParam("back_url") String back_url, //  The callback address       
    @RequestBody TestEntity json_data // json Data, for java Entity class  
){//... 

This is a request mapping method, and then use the browser input url: http: / / 127.0.0.1:8080 / test/doThis & # 63; id=1 & back_url=url & json_data={"code":2,"message":"test"}

In this method, @RequestParam is used to get the arguments and then @RequestBody is used to convert the arguments in json format to the Java type

Error detected while running: Required request body is missing

Using @RequestBody requires loading MappingJackson2HttpMessageConverter, but the official documentation for SpringBoot mentions that this is loaded by default, and json string and javabean have no written errors

Therefore, considering that Content-ES41en should be requested, spring cannot find request body because there is no way to define ES43en-ES44en by typing url in the browser

To test this idea, write your own 1 request class:

String add_url = "http://127.0.0.1:8080/test/doThis"; 
  URL url = new URL(add_url); 
  HttpURLConnection connection = (HttpURLConnection)url.openConnection(); 
  connection.setDoInput(true); 
  connection.setDoOutput(true); 
  connection.setRequestMethod("POST"); 
  connection.setUseCaches(false); 
  connection.setInstanceFollowRedirects(true); 
  connection.setRequestProperty("Content-Type","application/json"); 
  connection.connect(); 
  DataOutputStream out = new DataOutputStream(connection.getOutputStream()); 
  JSONObject obj = new JSONObject(); 
   
  obj.put("code", -1002);    
  obj.put("message", "msg"); 
  out.writeBytes(obj.toString()); 
  out.flush(); 
  out.close(); 

The request still fails. After debugging, it is found that all @RequestParam annotations need to be removed to succeed

conclusion

1. @RequestBody needs to parse all request parameters as json, so it cannot include the writing of key=value. In request url, all request parameters are 1 json

2. When you enter url directly through the browser, the object of json cannot be obtained by @RequestBody. You need to use java programming or request based on ajax method, set ES71en-ES72en to application/json

That's all I have to say about the correct way to use @RequestBody in this article, and I hope it helps. Interested friends can continue to refer to other related topics in this site, if there is any deficiency, welcome to comment out. Thank you for your support!