Spring Boot 3 入门指南：30 分钟搭建 REST API

Spring Boot 是 Java 最流行的 Web 框架。本文带你从零搭建一个 REST API。

创建项目

使用 Spring Initializr 或命令行：

curl https://start.spring.io/starter.zip \
  -d type=maven-project \
  -d language=java \
  -d bootVersion=3.2.0 \
  -d dependencies=web,validation,jpa \
  -o demo.zip

项目结构

src/main/java/com/example/
├── Application.java
├── controller/
│   └── UserController.java
├── service/
│   └── UserService.java
├── repository/
│   └── UserRepository.java
├── entity/
│   └── User.java
└── dto/
    └── UserDTO.java

创建实体

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(nullable = false)
    private String name;
    
    @Column(unique = true)
    private String email;
    
    // getters, setters
}

创建 Repository

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByEmail(String email);
}

创建 Service

@Service
@Transactional
public class UserService {
    @Autowired
    private UserRepository userRepository;
    
    public List<User> findAll() {
        return userRepository.findAll();
    }
    
    public User findById(Long id) {
        return userRepository.findById(id)
            .orElseThrow(() -> new RuntimeException("用户不存在"));
    }
    
    public User create(User user) {
        return userRepository.save(user);
    }
}

创建 Controller

@RestController
@RequestMapping("/api/users")
public class UserController {
    @Autowired
    private UserService userService;
    
    @GetMapping
    public List<User> findAll() {
        return userService.findAll();
    }
    
    @GetMapping("/{id}")
    public User findById(@PathVariable Long id) {
        return userService.findById(id);
    }
    
    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public User create(@Valid @RequestBody User user) {
        return userService.create(user);
    }
    
    @PutMapping("/{id}")
    public User update(@PathVariable Long id, @Valid @RequestBody User user) {
        user.setId(id);
        return userService.create(user);
    }
    
    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void delete(@PathVariable Long id) {
        userService.delete(id);
    }
}

全局异常处理

@RestControllerAdvice
public class GlobalExceptionHandler {
    
    @ExceptionHandler(RuntimeException.class)
    public ResponseEntity<ErrorResponse> handleRuntime(RuntimeException e) {
        return ResponseEntity.badRequest()
            .body(new ErrorResponse(400, e.getMessage()));
    }
    
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ErrorResponse> handleValidation(MethodArgumentNotValidException e) {
        String message = e.getBindingResult().getFieldErrors().stream()
            .map(err -> err.getField() + ": " + err.getDefaultMessage())
            .collect(Collectors.joining(", "));
        return ResponseEntity.badRequest()
            .body(new ErrorResponse(400, message));
    }
}

配置文件

# application.yml
server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/demo
    username: root
    password: password
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true

运行和测试

# 运行
mvn spring-boot:run

# 测试
curl http://localhost:8080/api/users

总结

Spring Boot 简化了 Java Web 开发。通过分层架构（Controller → Service → Repository），可以快速搭建规范的 REST API。