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這篇文章主要介紹“java多次嵌套循環(huán)查詢數(shù)據(jù)庫(kù)導(dǎo)致代碼中數(shù)據(jù)處理慢如何解決”的相關(guān)知識(shí),小編通過(guò)實(shí)際案例向大家展示操作過(guò)程,操作方法簡(jiǎn)單快捷,實(shí)用性強(qiáng),希望這篇“java多次嵌套循環(huán)查詢數(shù)據(jù)庫(kù)導(dǎo)致代碼中數(shù)據(jù)處理慢如何解決”文章能幫助大家解決問(wèn)題。
代碼中有一部分代碼多次嵌套循環(huán)和數(shù)據(jù)處理,執(zhí)行速度很慢
通過(guò)多線程
private final static Executor executor = Executors.newFixedThreadPool(3);
即等待(await)count個(gè)線程或一個(gè)線程count次計(jì)數(shù),通過(guò)工作線程來(lái)countDown計(jì)數(shù)減一,直到計(jì)數(shù)為0,await阻塞結(jié)束;目的:保證所有線程都走完
final CountDownLatch latch = new CountDownLatch(dataList.size());
需要多線程的代碼寫在run中
@Override public void run() { //業(yè)務(wù)代碼處理 //countDown計(jì)數(shù)減一 latch.countDown(); }
// 等待所有工作線程結(jié)束 latch.await();
private final static Executor executor = Executors.newFixedThreadPool(3);//啟用多線程 public Result getList(@RequestBody StatusDbSelectParam param){ PageHelper.startPage(param.getPageNum(), param.getPageSize()); List<Map<String, Object>> dataList = statusDbService.selectByTime(tableName, columnNames.toString(), param.getStartTime(), param.getEndTime()); //初始化設(shè)置count,即等待(await)count個(gè)線程或一個(gè)線程count次計(jì)數(shù),通過(guò)工作線程來(lái)countDown計(jì)數(shù)減一,直到計(jì)數(shù)為0,await阻塞結(jié)束 final CountDownLatch latch = new CountDownLatch(dataList.size()); for(int k =0;k<dataList.size();k++) { final int i = k; String finalTableName = tableName; executor.execute(new Runnable() { @Override public void run() { try { Map<String, Object> map = dataList.get(i); for (String pid : map.keySet()) { String val = String.valueOf(map.get(pid)); String columPid = pid.substring(2, pid.length()).toLowerCase(); List<MonitorRuleEntity> list = monitorRuleService.listMonitorRule(columPid, finalTableName); String status = ""; //循環(huán)規(guī)則數(shù)據(jù) 判斷監(jiān)測(cè)點(diǎn)是否報(bào)警 更新狀態(tài) for (int j = 0; j < list.size(); j++) { Boolean flag = DevHealthStatusFactory.getInstance().getResultMapByRule(val, list.get(j)); if (flag) { if (j == 0) { status = "A"; break; } else if (j == 1) { status = "B"; break; } else if (j == 2) { status = "C"; break; } } } if (pid.equalsIgnoreCase(timeColumnName)) { map.put(pid, val); } else { map.put(pid, val + "_" + status); } } latch.countDown(); } catch (Exception e) { e.printStackTrace(); } } }); } try { // 等待所有工作線程結(jié)束 latch.await(); } catch (InterruptedException e) { e.printStackTrace(); } return ResultMsg.successMsg().data(new PageInfo<>(dataList)); }
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