自定义注解编写以及讲解（以异常处理为例）

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.ElementType.TYPE_USE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

@Documented
@Constraint(validatedBy = { ListValueConstraintValidataor.class })
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE })
@Retention(RUNTIME)
public @interface ListValue {
    String message() default "{com.atguigu.common.valid.ListValue.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    int[] vals() default {  };
}

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.util.HashSet;
import java.util.Set;

//ConstraintValidator<>注解种填写两个泛型，一个是自定义注解，一个是指标注在什么类型上
public class ListValueConstraintValidataor implements ConstraintValidator<ListValue, Integer> {

    private Set<Integer> set = new HashSet<>();

    /*
     *初始化方法
     *将注解内的值例如：@ListValue(vals = {0,1}）种0，1放入set中
     */
    @Override
    public void initialize(ListValue constraintAnnotation) {

        int[] vals = constraintAnnotation.vals();

        for (int val : vals) {
            set.add(val);
        }
    }

    /*
     * 判断是否校验成功
     * value是需要校验的值，本例种是Integer的值
     */
    @Override
    public boolean isValid(Integer value, ConstraintValidatorContext constraintValidatorContext) {
        return set.contains(value);
    }
}

import com.atguigu.common.valid.AddGroup;
import com.atguigu.common.valid.ListValue;
import com.atguigu.common.valid.UpadteGroup;
import com.atguigu.common.valid.UpadteStatusGroup;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;

import java.io.Serializable;
import java.util.Date;

import lombok.Data;
import org.hibernate.validator.constraints.URL;

import javax.validation.constraints.*;

/**
 * 品牌
 * 
 * @author chenshun
 * @email linchenguang@gmail.com
 * @date 2020-05-19 20:39:16
 */
@Data
@TableName("pms_brand")
public class BrandEntity implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * 品牌id
     */
    @NotNull(message = "修改必须指定品牌id",groups = {UpadteGroup.class})
    @Null(message = "新增必须指定品牌id",groups = {AddGroup.class})
    @TableId
    private Long brandId;
    /**
     * 品牌名
     */
    @NotBlank(message = "品牌名必须提交",groups = {AddGroup.class,UpadteGroup.class})
    private String name;
    /**
     * 品牌logo地址,新增时不能为空并且符合URL地址格式，而修改时可以为空但必须符合URL地址
     */
    @NotBlank(groups = {AddGroup.class})
    @URL(message = "必须上传正确图片",groups = {AddGroup.class,UpadteGroup.class})
    private String logo;
    /**
     * 介绍
     */
    private String descript;
    /**
     * 显示状态[0-不显示；1-显示]
     */
    @NotNull(groups = {AddGroup.class, UpadteStatusGroup.class})
    @ListValue(vals = {0,1},groups = {AddGroup.class, UpadteStatusGroup.class})
    private Integer showStatus;
    /**
     * 检索首字母
     */
    @NotEmpty(groups = {AddGroup.class})
    @Pattern(regexp = "^[a-zA-Z]$",message = "范围必须在a-z或A-Z之间",groups = {AddGroup.class,UpadteGroup.class})
    private String firstLetter;
    /**
     * 排序
     */
    @NotNull(groups = {AddGroup.class})
    @Min(value = 0,message = "排序必须大于等于0",groups = {AddGroup.class,UpadteGroup.class})
    private Integer sort;

}

com.atguigu.common.valid.ListValue.message = 传入值出错