目录

• • 前言
  • 使用
  • • 完成了就通知我
    • 异步执行任务
    • 流式调用
    • 异常处理
    • 组合多个CompletableFuture
  • 小结

前言

• CompletableFuture是Java8新增的一个功能十分强大的工具类，它一方面实现了Future接口，另一方面也实现了CompletionStage接口，CompletionStage接口多达40中方法，为我们函数式编程
  流式调用提供支持。相较于FutureTask来做多任务更简洁了。

使用

完成了就通知我

• 核心代码

/*** 完成了就通知我 ，手动** @return*/public String completeNotify() {CompletableFuture future = new CompletableFuture<>();threadPoolTaskExecutor.execute(new AskThread(future));try {Integer result = future.get();System.out.println("result " + result);return result.toString();} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}}class AskThread implements Runnable {CompletableFuture future;public AskThread(CompletableFuture future) {this.future = future;}@Overridepublic void run() {int res = 0;try {// 模拟长时间计算过程Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}res = 100;// 通知完成future.complete(res);}}

• 之前我利用这个功能完成了 高并发场景下请求合并(批量)
  的功能，可以参考下。

异步执行任务

• 核心代码

     public String asyncTask() {StopWatch stopWatch = new StopWatch("asyncTask");stopWatch.start("task");// 如果是runAsync 没有返回值CompletableFuture future = CompletableFuture.supplyAsync(() -> calc(50), threadPoolTaskExecutor);CompletableFuture futureTwo = CompletableFuture.supplyAsync(() -> calc(60), threadPoolTaskExecutor);int result = 0;int res = 0;try {result = future.get();res = futureTwo.get();} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}System.out.println(result + " " + res);stopWatch.stop();System.out.println(stopWatch.prettyPrint());System.out.println(stopWatch.getLastTaskTimeMillis());return result + " " + res;}public int calc(int param) {try {// 模拟耗时Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}if (EXCEPTION_PARAM == param){throw new RuntimeException("传了异常参数 "+param);}return param * 2;}

流式调用

    public String stream() {CompletableFuture future = CompletableFuture.supplyAsync(() -> calc(50), threadPoolTaskExecutor).thenApply((i) -> Integer.toString(i)).thenApply((str) -> "res " + str).thenAccept(System.out::println);try {future.get();} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}return "done";}

异常处理

     public String exception() {CompletableFuture future = CompletableFuture.supplyAsync(() -> calc(10)).exceptionally(ex -> {System.out.println("异常信息 " + ex.toString());return 0;}).thenApply((i) -> Integer.toString(i)).thenApply((str) -> "res " + str).thenAccept(System.out::println);try {future.get();} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}return "done";}

组合多个CompletableFuture

   public String compose(){CompletableFuture future = CompletableFuture.supplyAsync(()->calc(50),threadPoolTaskExecutor).thenCompose((i)->CompletableFuture.supplyAsync(()->calc(i),threadPoolTaskExecutor)).thenApply((str)->"res " + str).thenAccept(System.out::println);try {future.get();} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}return "done";}

小结

• CompletableFuture很强大，如果写异步任务相比FutureTask更简洁。
• 源码地址：https://github.com/1030907690/CompletableFuture-Sample
• 视频地址：https://www.bilibili.com/video/BV1B24y1C7bT/