shardingsphere 自定义分片策略

1、编写自定义分片类 采用精确分片算法实现PreciseShardingAlgorithm

package com.spring.config;

import org.apache.shardingsphere.api.sharding.standard.PreciseShardingAlgorithm;
import org.apache.shardingsphere.api.sharding.standard.PreciseShardingValue;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

import java.util.Collection;

@Component
public class UserAlgorithm implements PreciseShardingAlgorithm<String> {


    @Override
    public String doSharding(Collection<String> tableNames, PreciseShardingValue<String> preciseShardingValue) {
        if(!StringUtils.isEmpty(preciseShardingValue)){
            String shardingValue = preciseShardingValue.getValue();
            int index = getIndex(shardingValue);
            for(String name : tableNames){
                if(name.endsWith(index+"")){
                    return name;
                }
            }

        }

        return null;
    }


    private int getIndex(String uid){
        uid = uid.replace("-","");
        int res =  Math.abs(uid.hashCode())%10;
        return res;
    }
}

数据库中建了10张表 根据用户ID（为UUID）的hashcode 然后取模于 表的数量
doSharding(Collection tableNames, PreciseShardingValue preciseShardingValue) 参数说明：
tableNames 为当前所有的表名,preciseShardingValue 为当前分片字段的值

2、定义完后再配置文件中 指定下自定义配置的类文件（需要指定两个属性值）

#分片字段名称
spring.shardingsphere.sharding.tables.t_user.table-strategy.standard.sharding-column=user_id
分片策略自定义对应的类名
spring.shardingsphere.sharding.tables.t_user.table-strategy.standard.precise-algorithm-class-name=com.spring.config.UserAlgorithm

对应shardingsphere版本

        <dependency>
            <groupId>org.apache.shardingsphere</groupId>
            <artifactId>sharding-jdbc-spring-boot-starter</artifactId>
            <version>4.0.0-RC1</version>
        </dependency>