Spring data CrudRepository 的保存方法和更新

Spring Data: CrudRepository的保存与更新方法详解

java
@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String username;
    private String email;
    // 省略构造函数、getter和setter等
}

java
public interface UserRepository extends CrudRepository {
}

java
@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
    public void saveOrUpdateUser(User user) {
        userRepository.save(user);
    }
}

java
public class UpdateExample {
    public static void main(String[] args) {
        // 创建一个新用户
        User newUser = new User();
        newUser.setUsername("JohnDoe");
        newUser.setEmail("john.doe@example.com");
        // 保存新用户
        userRepository.save(newUser);
        // 查询并获取已保存的用户
        User existingUser = userRepository.findById(newUser.getId()).orElse(null);
        if (existingUser != null) {
            // 修改用户信息
            existingUser.setEmail("john.doe.updated@example.com");
            // 使用save方法更新用户数据
            userRepository.save(existingUser);
        }
    }
}