mall/mall-service/src/main/java/com/txz/mall/configurer/UserIdTableShardingAlgorithm.java

package com.txz.mall.configurer;

import org.apache.shardingsphere.api.sharding.standard.PreciseShardingAlgorithm;
import org.apache.shardingsphere.api.sharding.standard.PreciseShardingValue;

import java.util.Collection;

public class UserIdTableShardingAlgorithm implements PreciseShardingAlgorithm<Long> {

    @Override
    public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Long> shardingValue) {

        long lastFourDigits = getLastFourDigits(shardingValue.getValue());
        // 用户ID取模5，分配到0-4表
        long mod = lastFourDigits % 5;
        for (String tableName : availableTargetNames) {
            if (tableName.endsWith(String.valueOf(mod))) {
                return tableName;
            }
        }
        throw new IllegalArgumentException("未找到匹配的表: " + availableTargetNames + ", 分片值: " + shardingValue);
    }


    // 获取user_id后四位
    private long getLastFourDigits(Long value) {
        if (value == null ) return 0L;
        return value % 10000 ;
    }

}