<!-- 添加 JSR-303 Bean Validation 依賴 -->
<dependency>
    <groupId>javax.validation</groupId>
    <artifactId>validation-api</artifactId>
    <version>2.0.1.Final</version>
</dependency>
<!-- Hibernate Validator 的實(shí)現(xiàn) --> 
<dependency>
    <groupId>org.hibernate.validator</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>6.1.5.Final</version>
</dependency>

public class User {
    @NotNull(message="用戶名不能為空")
    private String username;
    @NotNull(message="密碼不能為空")
    @Size(min=6, max=20, message="密碼長(zhǎng)度應(yīng)該在6到20位")   
    private String password;
    // getter 和 setter 方法
}

@RestController
@RequestMapping("/user")
public class UserController {
    @PostMapping("/register")
    public CommonResult<User> register(@RequestBody @Validated User user) {
        return CommonResult.success(user);
    }
}

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(value = MethodArgumentNotValidException.class)
    public CommonResult<Object> handleMethodArgumentNotValidException(MethodArgumentNotValidException ex){
        List<ObjectError> errors = ex.getBindingResult().getAllErrors();
        StringBuilder errorMsg = new StringBuilder();
        errors.forEach(error -> errorMsg.append(error.getDefaultMessage()).append("; "));
        return CommonResult.fail(ResultCode.PARAM_VALID_ERROR.getCode(), errorMsg.toString(), null);
    }
    @ExceptionHandler(value = Exception.class)
    public CommonResult<Object> handleException(Exception ex){
        log.error("系統(tǒng)發(fā)生異常：", ex);
        return CommonResult.fail(ResultCode.SYSTEM_ERROR.getCode(), ResultCode.SYSTEM_ERROR.getMsg(), null);
    }
}

public enum ResultCode {
    SUCCESS(200, "操作成功"),
    PARAM_VALID_ERROR(400, "參數(shù)校驗(yàn)失敗"),
    UNAUTHORIZED(401, "未認(rèn)證"),
    FORBIDDEN(403, "無權(quán)限"),
    SYSTEM_ERROR(500, "服務(wù)器內(nèi)部錯(cuò)誤");
    private int code;
    private String msg;
    ResultCode(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }
    public int getCode() {
        return code;
    }
    public String getMsg() {
        return msg;
    }
}
public class CommonResult<T> {
    private int code;
    private String msg;
    private T data;
    public CommonResult() {}
    public CommonResult(int code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }
    public static <T> CommonResult<T> success(T data) {
        return new CommonResult<T>(ResultCode.SUCCESS.getCode(), ResultCode.SUCCESS.getMsg(), data);
    }
    public static <T> CommonResult<T> fail(ResultCode resultCode) {
        return new CommonResult<T>(resultCode.getCode(), resultCode.getMsg(), null);
    }
    public static <T> CommonResult<T> fail(ResultCode resultCode, T data) {
        return new CommonResult<T>(resultCode.getCode(), resultCode.getMsg(), data);
    }
    // getter 和 setter 方法
}

@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Constraint(validatedBy = {AgeValidator.class})
public @interface Age {
    String message() default "年齡不在合法范圍內(nèi)";
    int minAge() default 0;
    int maxAge() default 150;
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}
public class AgeValidator implements ConstraintValidator<Age, Integer> {
    private int minAge;
    private int maxAge;
    @Override
    public void initialize(Age constraintAnnotation) {
        this.minAge = constraintAnnotation.minAge();
        this.maxAge = constraintAnnotation.maxAge();
    }
    @Override
    public boolean isValid(Integer value, ConstraintValidatorContext context) {
        if(value == null) {
            return true; // 允許為空值
        }
        if(value < minAge || value > maxAge) {
            return false; // 驗(yàn)證不通過
        }
        return true; // 驗(yàn)證通過
    }
}
public class User {
    @NotNull(message="用戶名不能為空")
    private String username;
    @Age(message="年齡不在合法范圍內(nèi)", minAge=0, maxAge=120)
    private Integer age;
    // getter 和 setter 方法
}