made some changes in my controller

server/src/main/java/com/example/demo/user/UserController.java

 package com.example.demo.user;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.*;
 
 
     @Autowired // this means to get bean called userRepository which is auto-generated by spring. it is ued to handle data
     private UserRepository userRepository;
-
+        ObjectMapper om = new ObjectMapper();
 
     @PostMapping(path="/add")
-    public @ResponseBody String addNewUser(@RequestParam String username, @RequestParam String email, @RequestParam String password){ //ResponseBody means the returned string is the response
+    //public @ResponseBody String addNewUser(@RequestParam String username, @RequestParam String email, @RequestParam String password){ //ResponseBody means the returned string is the response
         //RequestParam means it is a parameter from a GET or POST request
-        User n = new User(username, email, password);
-        userRepository.save(n);
-        return "Saved";
+      public @ResponseBody String addNewuser(@RequestBody User user) {
+        userRepository.save(user);
+        return "saved";
     }
 
     @GetMapping(path="/all")