<dependency>
    <groupId>jakarta.validation</groupId>
    <artifactId>jakarta.validation-api</artifactId>
    <version>3.0.2</version>
</dependency>
<!-- 實(shí)現(xiàn) (如 Hibernate Validator) -->
<dependency>
    <groupId>org.hibernate.validator</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>8.0.1.Final</version>
</dependency>

public class User {
    @NotNull(message = "用戶名不能為空")
    @Size(min = 3, max = 20, message = "用戶名長(zhǎng)度必須在3-20之間")
    private String username;
    @Email(message = "郵箱格式不正確")
    private String email;
    @Min(value = 18, message = "年齡必須大于18歲")
    private int age;
    // getters and setters
}

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
User user = new User();
user.setUsername("ab"); // 太短
user.setEmail("invalid-email");
user.setAge(17);
Set<ConstraintViolation<User>> violations = validator.validate(user);
for (ConstraintViolation<User> violation : violations) {
    System.out.println(violation.getPropertyPath() + ": " + violation.getMessage());
}

@RestController
@RequestMapping("/users")
public class UserController {
    @PostMapping
    public ResponseEntity<String> createUser(@Valid @RequestBody User user) {
        // 如果驗(yàn)證失敗，會(huì)拋出MethodArgumentNotValidException
        return ResponseEntity.ok("用戶創(chuàng)建成功");
    }
}

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<Map<String, String>> handleValidationExceptions(
        MethodArgumentNotValidException ex) {
        Map<String, String> errors = new HashMap<>();
        ex.getBindingResult().getAllErrors().forEach((error) -> {
            String fieldName = ((FieldError) error).getField();
            String errorMessage = error.getDefaultMessage();
            errors.put(fieldName, errorMessage);
        });
        return ResponseEntity.badRequest().body(errors);
    }
}

@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = PhoneNumberValidator.class)
public @interface PhoneNumber {
    String message() default "無(wú)效的電話號(hào)碼";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

public class PhoneNumberValidator implements ConstraintValidator<PhoneNumber, String> {
    private static final Pattern PHONE_PATTERN = Pattern.compile("^1[3-9]\\d{9}$");
    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if (value == null) {
            return true; // 使用@NotNull處理null值
        }
        return PHONE_PATTERN.matcher(value).matches();
    }
}

public class ContactInfo {
    @PhoneNumber
    private String phone;
    // getter and setter
}

public interface BasicInfo {}
public interface AdvancedInfo {}
public class User {
    @NotNull(groups = BasicInfo.class)
    private String username;
    @Email(groups = AdvancedInfo.class)
    private String email;
}
// 使用分組驗(yàn)證
Set<ConstraintViolation<User>> violations = validator.validate(user, BasicInfo.class);

public class Order {
    @Valid
    private List<OrderItem> items;
}
public class OrderItem {
    @NotNull
    private String productId;
    @Min(1)
    private int quantity;
}

@Size(min = 6, max = 20, message = "密碼長(zhǎng)度必須在 {min} 到 {max} 之間")
private String password;

public class UserService {
    @Validated
    public void createUser(@Valid User user) {
        // ...
    }
    @Valid
    public User getUser(@NotNull Long id) {
        // ...
    }
}