java怎么验证用户输入的参数 参数校验与异常提示的最佳实践

public class UserRequest {
    @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 = "年龄不能小于18岁")
    private Integer age;
}

@PostMapping("/users")
public ResponseEntity<String> createUser(@Valid @RequestBody UserRequest request) {
    // 业务逻辑
    return ResponseEntity.ok("创建成功");
}

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<Map<String, Object>> handleValidationExceptions(
            MethodArgumentNotValidException ex) {
        Map<String, Object> errors = new HashMap<>();
        errors.put("status", 400);
        errors.put("message", "参数校验失败");

        List<String> errorList = ex.getBindingResult()
                .getFieldErrors()
                .stream()
                .map(error -> error.getField() + ": " + error.getDefaultMessage())
                .collect(Collectors.toList());

        errors.put("errors", errorList);
        return ResponseEntity.badRequest().body(errors);
    }
}

{
  "status": 400,
  "message": "参数校验失败",
  "errors": ["username: 用户名不能为空", "age: 年龄不能小于18岁"]
}

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

public class PhoneValidator implements ConstraintValidator<Phone, String> {
    private static final String PHONE_REGEX = "^1[3-9]\d{9}$";

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if (value == null) return true; // 可为空由 @NotNull 控制
        return value.matches(PHONE_REGEX);
    }
}

@Phone(message = "请输入正确的手机号")
private String phone;

if (userRepository.existsByUsername(request.getUsername())) {
    throw new BusinessException("用户名已存在");
}