教你巧用mysql位运算解决多选值存储的问题

## 例1：判断用户是否开启了密码认证--1 (满足条件时返回查询结果，没有满足条件时返回为空)
Select * from user where auth_method & 1;

## 例2：判断用户是否开启了密码认证 + 短信认证 (1+2)
Select * from user where auth_method & 3;

## 例2：判断用户是否开启了密码认证 + 短信认证 + 扫码认证 (1+2+4)
Select * from user where auth_method & 7;

import com.google.common.collect.Lists;
import lombok.Getter;
import org.springframework.util.CollectionUtils;

import java.util.Arrays;
import java.util.List;

@Getter
public enum AuthMethodEnum {

    PASSWORD(1, "密码认证"),
    SMS(2, "短信认证"),
    QR_CODE(4, "扫码认证");

    private Integer method;

    private String name;

    AuthMethodEnum(Integer method, String name) {
        this.method = method;
        this.name = name;
    }

    /**
     * 将mysql存储值解析成多种认证方式
     * @param method
     * @return
     */
    public static List<Integer> parseAuthMethod(Integer method) {
        List<Integer> list = Lists.newArrayList();
        if (null == method) {
            return list;
        }
        AuthMethodEnum[] arr = AuthMethodEnum.values();
        // 需要先将method从大到小排序
        Arrays.sort(arr, (o1, o2) -> {
            if (o1.method > o2.method) {
                return -1;
            } else {
                return 0;
            }
        });
        for (AuthMethodEnum e : arr) {
            if (method >= e.method) {
                list.add(e.method);
                method = method - e.method;
            }
        }
        return list;
    }

    /**
     * 将任意种认证方式计算后得到存储值
     * @param methods
     * @return
     */
    public static Integer calculateAuthMethod(List<Integer> methods) {
        if (CollectionUtils.isEmpty(methods)) {
            return 0;
        }
        return methods.stream().mapToInt(p -> p).sum();
    }

    public static void main(String[] args) {
        System.out.println(parseAuthMethod(8));
    }
}