MainController.java

package com.example.accessingdatamysql;


import org.apache.coyote.Response;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.util.Map;
import java.util.Optional;

@CrossOrigin
@RestController // This means that this class is a Controller
@RequestMapping(path="/user") // This means URL's start with /demo (after Application path)
public class MainController {
    @Autowired // This means to get the bean called userRepository
    // Which is auto-generated by Spring, we will use it to handle the data
    private UserRepository userRepository;


    @PostMapping(path = "/add") // Map ONLY POST Requests
    @ResponseBody
    public User addJsonUser(@RequestBody User usr) {
        // @ResponseBody means the returned String is the response, not a view name
        // @RequestParam means it is a parameter from the GET or POST request
        userRepository.save(usr);
        return usr;
    }

    @PutMapping(path = "/update")
    @ResponseBody
    public User updateUser(@RequestBody User usr)
    {
        userRepository.save(usr);
        return usr;
    }

    @PutMapping(path = "/changepass")
    @ResponseBody
    public User updateUser(@RequestBody Map<String, String> json)
    {
        if (json.get("email") != null)
        {
            Optional<User> user = userRepository.findById(json.get("email"));
            if (user.isPresent())
            {
                User usr = user.get();
                usr.setPassword(json.get("password"));
                userRepository.save(usr);
                return usr;
            }
            return null;
        }
        return null;
    }

    @GetMapping(path="/all")
    public @ResponseBody Iterable<User> getAllUsers() {
        // This returns a JSON or XML with the users
        return userRepository.findAll();
    }

    @GetMapping(path = "/user")
    public @ResponseBody Optional<User> getUser(@RequestBody Map<String, String> json)
    {
        String email = json.get("email");
        return userRepository.findById(email);
    }

    @DeleteMapping(path = "/delete")
    public @ResponseBody User deleteUser(@RequestBody Map<String, String> json)
    {
        User found = null;
        String email = json.get("email");
        Optional<User> optionalUser = userRepository.findById(email);

        if (optionalUser.isPresent())
        {
            System.out.println("in if statement");
            found = optionalUser.get();
            userRepository.deleteById(email);

            return found;
        }
        return null;
    }
}