JAVA一次性读取Mysql几十万条大数据的处理

谁借莪１个温暖的怀抱￠ 2022-05-17 23:27 1273阅读 0赞

## 前言 ##

不用说也知道，一次性读取出那么大的数据是疯了吗，虚拟机能承受的聊那么大的对象吗？，所以我们需要分批进行读取。

下面是使用fenduan 每1万条进行一次读取执行

## 1、传入总数和每多少进行分段 制作为map ##

package com.duodian.youhui.admin.utils;
    
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.stereotype.Service;
    
    import java.util.TreeMap;
    
    
    @Service
    @Slf4j
    public class JavaHeapSpaceUtilsForCouponGood {
    
        /**
         * @Desc: 传入总数和每多少进行分段
         * @Date:  2018/8/28 下午1:36.
         */
        
        public static TreeMap<Long,Long> getStartIdAndEndId(Long count, Long fenduan){
            TreeMap<Long,Long> map = new TreeMap();
            Long num = count / fenduan;
            Long yushu = count % fenduan;
    
            for (int i = 1; i <= num; i++) {
                map.put((i - 1) * fenduan + 1, i * fenduan);
            }
    
            Long yushufinal = num * fenduan + yushu;
            map.put(num * fenduan + 1, yushufinal);
    
            return map ;
        }
    
    }

## 2、开始执行 ##

package com.duodian.youhui.admin.moudle.xiaodang.impl;
    
    import com.duodian.youhui.admin.moudle.coupon.service.CouponItemGoodService;
    import com.duodian.youhui.admin.moudle.xiaodang.XiaoDangService;
    import com.duodian.youhui.admin.moudle.xiaodang.XiaoDuoDataInsertService;
    import com.duodian.youhui.admin.utils.JavaHeapSpaceUtilsForCouponGood;
    import com.duodian.youhui.data.xiaodang.XiaodangInsertData;
    import com.duodian.youhui.entity.db.coupon.CouponItemGood;
    import com.duodian.youhui.entity.db.coupon.CouponItemGoodAttachment;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.stereotype.Service;
    
    import javax.annotation.Resource;
    import java.util.Collections;
    import java.util.List;
    import java.util.Map;
    import java.util.TreeMap;
    
    /**
     * @Description
     * @Author HealerJean
     * @Date 2018/4/19  下午1:58.
     */
    @Service
    @Slf4j
    public class XiaoDangServiceImpl implements XiaoDangService {
    
        //多点数据源
        @Resource
        private CouponItemGoodService  couponItemGoodService ;
    
        //小当数据源
        @Resource
       private XiaoDuoDataInsertService xiaoDuoDataInsertService;
    
    public void keyTransferToXiaoDang(Long taobaoUserInfoId) {
    
        //获取所有的相关的 id，默认是有顺序的，正常我们根据需要进行根据我们需求进行id排序
        List<Long> ids = couponItemGoodService.countAllCouponItemGood();
        TreeMap<Long,Long> map = JavaHeapSpaceUtilsForCouponGood.getStartIdAndEndId(Long.valueOf(ids.size()),10000L );
    
    
        for(Long key:map.keySet()){
            //在ids 进行划分。然后获取
            List<Long> idParams = ids.subList(key.intValue()-1, map.get(key).intValue());
    
            XiaodangInsertData xiaodangInsertData = couponItemGoodService.keyTransferToXiaoDuo(taobaoUserInfoId ,idParams);
            for(CouponItemGood couponItemGood : xiaodangInsertData.getCouponItemGoods()){
                try {
                    List<CouponItemGoodAttachment> couponItemGoodAttachments = couponItemGoodService.couponItemGoodAttachments(couponItemGood.getId());
                    xiaoDuoDataInsertService.insertCouponItemGood(couponItemGood,couponItemGoodAttachments, xiaodangInsertData.getTaobaoUserInfo());
                }catch (Exception e){
                    log.error("迁移过程中的异常"+couponItemGood.getId()+":"+e.getMessage());
                    continue;
                }
            }
            log.info(key + "到" + map.get(key) + "迁移完成");
        }
    
    
    
    
    }

![ContactAuthor][]

[ContactAuthor]: /images/20220518/60d6e4e39ff645979d84d859901fbade.png