Creating Controller Layer
Create a UserController class under package springmvc_example.controller package and write the following code in it 

package springmvc_example.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import springmvc_example.model.User;
import springmvc_example.service.UserService;

@RestController
public class UserController {

 @Autowired
 UserService userService;
 
 @RequestMapping(value="/user/", method=RequestMethod.GET, headers="Accept=application/json")
 public @ResponseBody List getListUser(){
  List users = userService.getListUser();
  
  return users;
 }
 
 @RequestMapping(value="/add/", method=RequestMethod.POST)
 public @ResponseBody User add(@RequestBody User user){
  userService.saveOrUpdate(user);
  
  return user;
 }
 
 @RequestMapping(value="/update/{id}", method=RequestMethod.PUT)
 public @ResponseBody User update(@PathVariable("id") int id, @RequestBody User user){
  user.setId(id);
  userService.saveOrUpdate(user);
  
  return user;
 }
 
 @RequestMapping(value="/delete/{id}", method=RequestMethod.DELETE)
 public @ResponseBody User delete(@PathVariable("id") int id){
  User user = userService.findUserById(id);
  userService.deleteUser(id);
  
  return user;
 }
 
}