@Data
@ApiModel(description = "分頁請求參數(shù)")
@Accessors(chain = true)
public class PageQuery {
    public static final Integer DEFAULT_PAGE_SIZE = 20;
    public static final Integer DEFAULT_PAGE_NUM = 1;

    @ApiModelProperty(value = "頁碼", example = "1")
    @Min(value = 1, message = "頁碼不能小于1")
    private Integer pageNo = DEFAULT_PAGE_NUM;

    @ApiModelProperty(value = "每頁大小", example = "5")
    @Min(value = 1, message = "每頁查詢數(shù)量不能小于1")
    private Integer pageSize = DEFAULT_PAGE_SIZE;

    @ApiModelProperty(value = "是否升序", example = "true")
    private Boolean isAsc = true;

    @ApiModelProperty(value = "排序字段", example = "id")
    private String sortBy;

    public int from(){
        return (pageNo - 1) * pageSize;
    }

    public <T> Page<T> toMpPage(OrderItem ... orderItems) {
        Page<T> page = new Page<>(pageNo, pageSize);
        // 是否手動指定排序方式
        if (orderItems != null && orderItems.length > 0) {
            for (OrderItem orderItem : orderItems) {
                page.addOrder(orderItem);
            }
            return page;
        }
        // 前端是否有排序字段
        if (StringUtils.isNotEmpty(sortBy)){
            OrderItem orderItem = new OrderItem();
            orderItem.setAsc(isAsc);
            orderItem.setColumn(sortBy);
            page.addOrder(orderItem);
        }
        return page;
    }

    public <T> Page<T> toMpPage(String defaultSortBy, boolean isAsc) {
        if (StringUtils.isBlank(sortBy)){
            sortBy = defaultSortBy;
            this.isAsc = isAsc;
        }
        Page<T> page = new Page<>(pageNo, pageSize);
        OrderItem orderItem = new OrderItem();
        orderItem.setAsc(this.isAsc);
        orderItem.setColumn(sortBy);
        page.addOrder(orderItem);
        return page;
    }
    public <T> Page<T> toMpPageDefaultSortByCreateTimeDesc() {
        return toMpPage(Constant.DATA_FIELD_NAME_CREATE_TIME, false);
    }
}

public Page<User> getUserList(PageQuery query) {
    Page<User> page = query.toMpPage();
    return userMapper.selectPage(page, new QueryWrapper<>());
}

@PostMapping("/create")
public Result createCoupon(@Valid @RequestBody CouponFormDTO dto) {
    // 業(yè)務(wù)邏輯
}

@Data
public class CouponFormDTO {
    @NotNull(message = "優(yōu)惠券類型不能為空")
    private Integer couponType;
    
    @Range(min=1, max=10, message="限領(lǐng)數(shù)量超出范圍")
    private Integer limitCount;
    
    @EnumValid(enumeration = {0,1}, message="領(lǐng)取方式非法")
    private ReceiveEnums receiveType;
}

@PostMapping("/update")
public Result update(@Validated(UpdateGroup.class) @RequestBody UserDTO userDTO) {
    // 業(yè)務(wù)邏輯處理
}

CREATE TABLE coupon (
    status TINYINT COMMENT '0-未激活 1-已生效 2-已過期'
)

if (!Arrays.asList(0,1,2).contains(status)) {
    throw new IllegalArgumentException();
}

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = EnumValidator.class)
public @interface EnumValid {
    int[] value() default {};
    String message() default "非法枚舉值";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

public class EnumValidator implements ConstraintValidator<EnumValid, Integer> {
    private Set<Integer> allowedValues = new HashSet<>();

    @Override
    public void initialize(EnumValid constraintAnnotation) {
        Arrays.stream(constraintAnnotation.value())
              .forEach(allowedValues::add);
    }

    @Override
    public boolean isValid(Integer value, ConstraintValidatorContext context) {
        if (value == null) return true;
        return allowedValues.contains(value);
    }
}

/**
 * 實現(xiàn)后在接口訪問時如果接口實現(xiàn)了這個接口
 * 會被自動自行接口check進(jìn)行校驗
 **/
public interface Checker<T> {

    /**
     * 用于實現(xiàn)validation不能校驗的數(shù)據(jù)邏輯
     */
    default void check(){

    }

    default void check(T data){
    }
}

Data
@ApiModel(description = "章節(jié)")
public class CataSaveDTO implements Checker {
    @ApiModelProperty("章、節(jié)、練習(xí)id")
    private Long id;
    @ApiModelProperty("目錄類型1：章，2：節(jié)，3：測試")
    @NotNull(message = "")
    private Integer type;
    @ApiModelProperty("章節(jié)練習(xí)名稱")
    private String name;
    @ApiModelProperty("章排序，章一定要傳，小節(jié)和練習(xí)不需要傳")
    private Integer index;

    @ApiModelProperty("當(dāng)前章的小節(jié)或練習(xí)")
    @Size(min = 1, message = "不能出現(xiàn)空章")
    private List<CataSaveDTO> sections;

    @Override
    public void check() {
        //名稱為空校驗
        if(type == CourseConstants.CataType.CHAPTER && StringUtils.isEmpty(name)) {
            throw new BadRequestException(CourseErrorInfo.Msg.COURSE_CATAS_SAVE_NAME_NULL);
        }else if(StringUtils.isEmpty(name)){
            throw new BadRequestException(CourseErrorInfo.Msg.COURSE_CATAS_SAVE_NAME_NULL2);
        }
        //名稱長度問題
        if (type == CourseConstants.CataType.CHAPTER && name.length() > 30){
            throw new BadRequestException(CourseErrorInfo.Msg.COURSE_CATAS_SAVE_NAME_SIZE);
        }else if(name.length() > 30) {
            throw new BadRequestException(CourseErrorInfo.Msg.COURSE_CATAS_SAVE_NAME_SIZE2);
        }
        if(CollUtils.isEmpty(sections)){
            throw new BadRequestException("不能出現(xiàn)空章");
        }

    }
}

/**
 * 接口方法參數(shù)校驗器
 **/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface ParamChecker {
}

@Aspect
@Slf4j
@SuppressWarnings("all")
public class CheckerAspect {

    @Before("@annotation(paramChecker)")
    public void before(JoinPoint joinPoint, ParamChecker paramChecker) {
        Object[] args = joinPoint.getArgs();
        if(ArrayUtils.isNotEmpty(args)){
            //遍歷方法參數(shù)，參數(shù)是否實現(xiàn)了Checker接口
            for (Object arg : args){
                if(arg instanceof Checker) {
                    //調(diào)用check方法，校驗業(yè)務(wù)邏輯
                    ((Checker)arg).check();
                }else if(arg instanceof List){
                    //如果參數(shù)是一個集合也要校驗
                    CollUtils.check((List) arg);
                }
            }
        }
    }
}

    /**
     * 集合校驗邏輯
     *
     * @param data 要校驗的集合
     * @param checker 校驗器
     * @param <T> 集合元素類型
     */
    public static  <T> void  check(List<T> data, Checker<T> checker){
        if(data == null){
            return;
        }
        for (T t : data){
            checker.check(t);
        }
    }

    /**
     * 集合校驗邏輯
     *
     * @param data 要校驗的集合
     * @param <T> 集合元素類型
     */
    public static  <T extends Checker<T>> void  check(List<T> data){
        if(data == null){
            return;
        }
        for (T t : data){
            t.check();
        }
    }

  @PostMapping("baseInfo/save")
    @ApiOperation("保存課程基本信息")
    @ParamChecker
    //校驗非業(yè)務(wù)限制的字段
    public CourseSaveVO save(@RequestBody @Validated(CourseSaveBaseGroup.class) CourseBaseInfoSaveDTO courseBaseInfoSaveDTO) {
        return courseDraftService.save(courseBaseInfoSaveDTO);
    }