通过Streams并行执行多个查询

本文介绍了通过Streams并行执行多个查询的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有以下方法：

public String getResult() { List<String> serversList = getServerListFromDB(); List<String> appList = getAppListFromDB(); List<String> userList = getUserFromDB(); return getResult(serversList, appList, userList); }

这里我按顺序调用三个方法，然后点击DB并取出我结果，然后我对从DB命中获得的结果进行后处理。我知道如何通过使用 Threads 同时调用这三种方法。但我想使用Java 8 Parallel Stream 来实现这一目标。有人可以指导我如何通过Parallel Streams实现相同的目标吗？

Here I am calling three method sequentially which in turns hits the DB and fetch me results, then I do post processing on the results I got from the DB hits. I know how to call these three methods concurrently via use of Threads. But I would like to use Java 8 Parallel Stream to achieve this. Can someone please guide me how to achieve the same via Parallel Streams?

编辑我只想通过Stream并行调用这些方法。

EDIT I just want to call the methods in parallel via Stream.

private void getInformation() { method1(); method2(); method3(); method4(); method5(); }

推荐答案

您可以使用 CompletableFuture 这样：

public String getResult() { // Create Stream of tasks: Stream<Supplier<List<String>>> tasks = Stream.of( () -> getServerListFromDB(), () -> getAppListFromDB(), () -> getUserFromDB()); List<List<String>> lists = tasks // Supply all the tasks for execution and collect CompletableFutures .map(CompletableFuture::supplyAsync).collect(Collectors.toList()) // Join all the CompletableFutures to gather the results .stream() .map(CompletableFuture::join).collect(Collectors.toList()); // Use the results. They are guaranteed to be ordered in the same way as the tasks return getResult(lists.get(0), lists.get(1), lists.get(2)); }