Spring Boot 自动参数校验的实现步骤

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

public class UserDTO {
    @NotBlank(message = "用户名不能为空")
    private String username;
    @Email(message = "邮箱格式不正确")
    private String email;
    @Min(value = 18, message = "年龄必须大于18岁")
    private int age;
    @Pattern(regexp = "1[3-9]\\d{9}", message = "手机号格式不正确")
    private String phone;
    // Getter/Setter省略
}

@PostMapping("/create")
public ResponseEntity<?> createUser(@Valid @RequestBody UserDTO userDTO) {
    // 校验通过后执行业务逻辑
    return ResponseEntity.ok("用户创建成功");
}

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<Map<String, String>> handleValidationException(MethodArgumentNotValidException ex) {
        Map<String, String> errors = new HashMap<>();
        ex.getBindingResult().getFieldErrors().forEach(error -> {
            errors.put(error.getField(), error.getDefaultMessage());
        });
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errors);
    }
}

{
    "username": "用户名不能为空",
    "email": "邮箱格式不正确"
}

public interface CreateGroup {}
public interface UpdateGroup {}

public class UserDTO {
    @NotNull(groups = UpdateGroup.class, message = "ID不能为空")
    private Long id;
    @NotBlank(groups = {CreateGroup.class, UpdateGroup.class})
    private String name;
}

@PostMapping("/update")
public void updateUser(@Validated(UpdateGroup.class) @RequestBody UserDTO dto) {
    // ...
}

@Target({FIELD})
@Retention(RUNTIME)
@Constraint(validatedBy = PhoneValidator.class)
public @interface ValidPhone {
    String message() default "手机号格式错误";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

public class PhoneValidator implements ConstraintValidator<ValidPhone, String> {
    @Override
    public boolean isValid(String phone, ConstraintValidatorContext context) {
        return phone != null && phone.matches("1[3-9]\\d{9}");
    }
}

curl -X POST http://localhost:8080/create \
-H "Content-Type: application/json" \
-d '{"username":"", "email":"invalid-email"}'

{
    "username": "用户名不能为空",
    "email": "邮箱格式不正确"
}

graph TD
    A[添加依赖] --> B[DTO添加校验注解]
    B --> C[Controller添加@Valid]
    C --> D[全局异常处理器]
    D --> E[返回错误信息]