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雪花算法介绍:
SnowFlake(雪花) 算法,是 Twitter 开源的分布式 id 生成算法。其核心思想就是:使用一个 64 bit 的 long 型
的数字作为全局唯一 id,其中
41bit作为毫秒数,10bit作为机器的id(5个bit是数据中心,5个bit是机器id),12bit作为毫秒内的流水号(即每毫秒内可以有2的12次方个流水号/id),最后还有一个符号位,永远是0
。在分布式系统中的应用十分广泛,且ID 引入了时间戳,基本上保持自增的,后面的代码中有详细的注解。
这是一种生成主键唯一id的策略,还有很多方法可以实现生成主键唯一id,如uuid,主键自增。甚至可以自己写出一个自己设定的算法来实现。
Mybatis-plus中的应用
在Mybatis-plus中我们有多种生成主键id的方法
AUTO(0), NONE(1), INPUT(2), ID_WORKER(3), UUID(4), ID_WORKER_STR(5);
在使用mybatis-plus时写在实体类的主键属性上的注解
@TableId(type = IdType.ID_WORKER)//默认主键唯一id实现 @TableId(type =
IdType.AUTO)//主键自增实现,数据库也要是自增的才有效 @TableId(type = IdType.INPUT)//自行配置id
@TableId(type = IdType.NONE)//未设置主键 @TableId(type = IdType.UUID)//设置全局唯一id uuid
@TableId(type = IdType.ID_WORKER_STR)//ID_WORKER字符串表示法