Spring Boot 实战

快速开始

Spring Boot 让创建 Spring 应用变得简单。

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

RESTful API

创建一个简单的 RESTful API 控制器。

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

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

    @GetMapping("/{id}")
    public User getUserById(@PathVariable Long id) {
        return userService.findById(id);
    }

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

    @PutMapping("/{id}")
    public User updateUser(@PathVariable Long id, @RequestBody User user) {
        user.setId(id);
        return userService.save(user);
    }

    @DeleteMapping("/{id}")
    public void deleteUser(@PathVariable Long id) {
        userService.deleteById(id);
    }
}

依赖注入

使用 Spring 的依赖注入功能。

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    // 方式二：构造器注入（推荐）
    private final EmailService emailService;

    public UserService(EmailService emailService) {
        this.emailService = emailService;
    }

    // 方式三：Setter 注入
    private SMSService smsService;

    @Autowired
    public void setSmsService(SMSService smsService) {
        this.smsService = smsService;
    }
}

分层架构

典型的 Spring Boot 分层架构：

Controller (控制层)
    ↓
Service (业务逻辑层)
    ↓
Repository/DAO (数据访问层)
    ↓
Database (数据库)

// Entity 实体类
@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String username;
    private String email;

    // getters and setters
}

// Repository 数据访问层
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    List<User> findByUsername(String username);
}

// Service 业务逻辑层
@Service
@Transactional
public class UserService {
    @Autowired
    private UserRepository userRepository;

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

// Controller 控制层
@RestController
@RequestMapping("/api")
public class UserController {
    @Autowired
    private UserService userService;
}

配置文件

application.yml

server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb
    username: root
    password: password
    driver-class-name: com.mysql.cj.jdbc.Driver

  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true

logging:
  level:
    root: INFO
    com.example: DEBUG

异常处理

全局异常处理。

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<ErrorResponse> handleResourceNotFound(
            ResourceNotFoundException ex) {
        ErrorResponse error = new ErrorResponse(
            "NOT_FOUND",
            ex.getMessage()
        );
        return new ResponseEntity<>(error, HttpStatus.NOT_FOUND);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleGenericException(
            Exception ex) {
        ErrorResponse error = new ErrorResponse(
            "INTERNAL_SERVER_ERROR",
            "服务器内部错误"
        );
        return new ResponseEntity<>(error, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}