首先先建立一個 Model:

package com.example.demo.model;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String email;

    public User() {}

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

  
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

建立Repo

package com.example.demo.repository;

import com.example.demo.model.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
}

建立Service

package com.example.demo.service;

import com.example.demo.model.User;
import com.example.demo.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public User createUser(User user) {
        return userRepository.save(user);
    }

    public List<User> getAllUsers() {
        return userRepository.findAll();
    }

    public Optional<User> getUserById(Long id) {
        return userRepository.findById(id);
    }

    public Optional<User> updateUser(Long id, User userDetails) {
        return userRepository.findById(id).map(user -> {
            user.setName(userDetails.getName());
            user.setEmail(userDetails.getEmail());
            return userRepository.save(user);
        });
    }

    public boolean deleteUser(Long id) {
        return userRepository.findById(id).map(user -> {
            userRepository.delete(user);
            return true;
        }).orElse(false);
    }
}

之後建立Controller

package com.example.demo.controller;

import com.example.demo.model.User;
import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Optional;

@RestController
@RequestMapping("/api/users")
public class UserController {

    @Autowired
    private UserService userService;

    @PostMapping
    public User createUser(@RequestBody User user) {
        return userService.createUser(user);
    }

    @GetMapping
    public List<User> getAllUsers() {
        return userService.getAllUsers();
    }

    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable Long id) {
        Optional<User> user = userService.getUserById(id);
        return user.map(value -> ResponseEntity.ok().body(value))
                .orElseGet(() -> ResponseEntity.notFound().build());
    }

    @PutMapping("/{id}")
    public ResponseEntity<User> updateUser(@PathVariable Long id, @RequestBody User userDetails) {
        Optional<User> updatedUser = userService.updateUser(id, userDetails);
        return updatedUser.map(value -> ResponseEntity.ok().body(value))
                .orElseGet(() -> ResponseEntity.notFound().build());
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
        boolean isDeleted = userService.deleteUser(id);
        if (isDeleted) {
            return ResponseEntity.ok().build();
        } else {
            return ResponseEntity.notFound().build();
        }
    }
}