还不会使用多线程优化代码执行效率?codefun教你在业务场景中使用CompletableFuture进行优化！

业务场景

我们先来从场景入手，具体的业务是这样的:我们需要从某的省的id去查询这个省份所有的县区，至于什么是县区呢？在DB中我们是这样定义的，也就是字段level = 3 的时候，就代表一个县的信息，然后呢：我们需要查询某个省份的所有县区的项目数，一个县区下可能有很多项目，也可能没有项目信息；

返回格式

{"msg": "操作成功","code": 200,"data": [{"pid": 2,"id": 4,"areaCode": "540121","projectCount": 1,"areaName": "某某县","investMoney": 0,"level": 3,"listMigSupportProjectItemVo": null,"migSupportProjectList": [{"areaCode": "540121","name": "测试01","reservoirs": "1","projectNum": "2","investPlan": "20000.0","type": "散居移民基础设施完善","status": "plan","acceptTime": null,"unitAfterHandover": null}]},{"pid": 23,"id": 24,"areaCode": "542221","projectCount": 3,"areaName": "乃某某某某县","investMoney": 0,"level": 3,"listMigSupportProjectItemVo": null,"migSupportProjectList": [{"areaCode": "542221","name": "项目A","reservoirs": "水库A","projectNum": "项目批准文号A","investPlan": "1000000.0","type": "就业创业能力建设","status": "implemented","acceptTime": "2023-02-01","unitAfterHandover": "单位B"},{"areaCode": "542221","name": "项目B","reservoirs": "水库B","projectNum": "项目批准文号B","investPlan": "2000000.0","type": "类型2","status": "implemented","acceptTime": "2024-03-01","unitAfterHandover": "孤帆候风进"},{"areaCode": "542221","name": "项目C","reservoirs": "水库C","projectNum": "项目批准文号C","investPlan": "3000000.0","type": "类型3","status": "implementation","acceptTime": null,"unitAfterHandover": null}]},{"pid": 23,"id": 25,"areaCode": "542222","projectCount": 2,"areaName": "扎囊县","investMoney": 0,"level": 3,"listMigSupportProjectItemVo": null,"migSupportProjectList": [{"areaCode": "542222","name": "项目D","reservoirs": "水库D","projectNum": "项目批准文号D","investPlan": "4000000.0","type": "类型1","status": "plan","acceptTime": "2026-03-01","unitAfterHandover": "单位D"},{"areaCode": "542222","name": "项目F","reservoirs": "水库F","projectNum": "项目批准文号F","investPlan": "6000000.0","type": "类型2","status": "plan","acceptTime": null,"unitAfterHandover": null}]},{"pid": 23,"id": 30,"areaCode": "542227","projectCount": 2,"areaName": "某某1县","investMoney": 0,"level": 3,"listMigSupportProjectItemVo": null,"migSupportProjectList": [{"areaCode": "542227","name": "项目E","reservoirs": "水库E","projectNum": "项目批准文号E","investPlan": "5000000.0","type": "类型2","status": "plan","acceptTime": "2023-07-08","unitAfterHandover": "规范打广告"},{"areaCode": "542227","name": "1111","reservoirs": "1","projectNum": "1","investPlan": "10000.0","type": null,"status": "plan","acceptTime": null,"unitAfterHandover": null}]}]
}

原始代码

具体的话呢，会返回这样的一个Json格式，可以看出，没有项目的县是不会被返回的，并且查询出来的项目信息回做一个合并的统计，具体的场景就是查询所有某个省所有level为3的信息，然后拿到它的区域编码然后去项目表中查询项目信息，也就是我们要执行很多查询的sql,根据区域编码去查询项目集合（每一个县区的编码都不一样），接下来看一下我们开始写的代码

public List<MigSupportProjectScreenVo> selectAllisBuildProjectByLowestLevel(MigSupportScreenBo migSupportScreenBo) {//先查询所有level = 3 的区域数据List<MigSupportProjectScreenVo> migSupportProjectScreenVos = screenSupportMapper.selectByLowestLevel();migSupportProjectScreenVos.forEach(item -> {item.setMigSupportProjectList(selectProjectListByid(item.getAreaCode(), migSupportScreenBo.getType()));});ArrayList<MigSupportProjectScreenVo> res = new ArrayList<>();migSupportProjectScreenVos.forEach(item->{if (item.getMigSupportProjectList().size()!=0){res.add(item);}});return res;
}//根据区域的code查询一个项目集合
private List<MigSupportProject> selectProjectListByid(String code, Integer type) {return migSupportProjectMapper.selectProjectType(code, type);
}

是单线程的代码，在循环里面调用sql，然后在APIFox中进行测试，在清除了Mybatis缓存的情况下

优化后的代码

经过优化，我们用了CompletableFuture进行性能的优化

public List<MigSupportProjectScreenVo> selectAllisBuildProjectByLowestLevel(MigSupportScreenBo migSupportScreenBo) {// 先查询所有level = 3 的区域数据List<MigSupportProjectScreenVo> migSupportProjectScreenVos = screenSupportMapper.selectByLowestLevel();// 使用 CompletableFuture 异步执行 selectProjectListByid 方法List<CompletableFuture<Void>> futures = new ArrayList<>();for (MigSupportProjectScreenVo item : migSupportProjectScreenVos) {CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> {item.setMigSupportProjectList(selectProjectListByid(item.getAreaCode(), migSupportScreenBo.getType()));return null;});futures.add(future);}// 等待所有异步任务完成CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();// 过滤掉没有项目的 MigSupportProjectScreenVo 对象List<MigSupportProjectScreenVo> res = migSupportProjectScreenVos.stream().filter(item -> item.getMigSupportProjectList().size() != 0).collect(Collectors.toList());return res;
}

使用forkerJoinPool的默认线程池进行优化，没有使用自定义线程池.

由此可见，速度肉眼可见的提升了!