package com.test.demo.springboottest.asynTest; import com.google.common.util.concurrent.FutureCallback; import com.google.common.util.concurrent.Futures; import com.google.common.util.concurrent.ListenableFuture; import com.google.common.util.concurrent.ListeningExecutorService; import com.google.common.util.concurrent.MoreExecutors; import io.netty.util.concurrent.DefaultEventExecutorGroup; import io.netty.util.concurrent.EventExecutorGroup; import io.netty.util.concurrent.Future; import io.netty.util.concurrent.GenericFutureListener; import java.util.concurrent.Callable; import java.util.concurrent.CompletableFuture; import java.util.concurrent.CountDownLatch; import java.util.concurrent.Executors; /** * @author wuyun * @Description: TODO * @date 2020/4/22 * @Version 1.0 */ public class FutureTest { public static void main(String[] args) { //同步调用模式 /* try { long l = System.currentTimeMillis(); int i = syncCalculate(); System.out.println("计算结果:" + i); System.out.println("主线程运算耗时:" + (System.currentTimeMillis() - l) + "ms"); } catch (Exception e) { e.printStackTrace(); } */ //Future 模式可以细分为将来式和回调式两种模式 //1.Future 模式 – 将来式 1 (这种将来式的 future 适用多个耗时操作并发执行的场景。) /* try { long l = System.currentTimeMillis(); EventExecutorGroup group = new DefaultEventExecutorGroup(4); Future<Integer> f = group.submit(new Callable<Integer>() { @Override public Integer call() throws Exception { System.out.println("执行耗时操作..."); timeConsumingOperation(); return 100; } }); // 其他耗时操作.. System.out.println("计算结果::" + f.get());//等待结果,线程将会被这一步阻塞 System.out.println("主线程运算耗时:" + (System.currentTimeMillis() - l) + "ms"); } catch (Exception e) { e.printStackTrace(); }*/ //2.Future 模式 – 将来式 2---Netty框架 //使用了 addListener 这样的方法为一个 future 结果添加回调,从而达到“当耗时操作完成后,自行触发钩子去执行打印操作”的效果。 // 主线程只耗费了不到 1s 的时间,整个过程没有被耗时操作阻塞,这才是异步编程的推荐方式:回调。 /*try { long l = System.currentTimeMillis(); EventExecutorGroup group = new DefaultEventExecutorGroup(4); Future<Integer> f = group.submit(new Callable<Integer>() { @Override public Integer call() throws Exception { System.out.println("执行耗时操作..."); timeConsumingOperation(); return 100; } }); f.addListener(new GenericFutureListener<Future<? super Integer>>() { @Override public void operationComplete(Future<? super Integer> future) throws Exception { System.out.println("计算结果::" + future.get()); } }); System.out.println("主线程运算耗时:" + (System.currentTimeMillis() - l) + "ms"); new CountDownLatch(1).await(); } catch (Exception e) { e.printStackTrace(); }*/ //guava-异步 /*try { long l = System.currentTimeMillis(); ListeningExecutorService service= MoreExecutors.listeningDecorator(Executors.newSingleThreadExecutor()); ListenableFuture<Integer> future = service.submit(new Callable<Integer>() { public Integer call() throws Exception { System.out.println("执行耗时操作..."); timeConsumingOperation(); return 100; } });//<1> Futures.addCallback(future, new FutureCallback<Integer>() { public void onSuccess(Integer result) { System.out.println("计算结果:" + result); } public void onFailure(Throwable throwable) { System.out.println("异步处理失败,e=" + throwable); } });//<2> System.out.println("主线程运算耗时:" + (System.currentTimeMillis() - l)+ "ms"); new CountDownLatch(1).await(); } catch (Exception e) { e.printStackTrace(); }*/ //由 Callback Hell 引出 Promise 模式 //jdk1.8 已经提供了一种更为高级的回调方式:CompletableFuture /*try { long l = System.currentTimeMillis(); CompletableFuture<Integer> completableFuture = CompletableFuture.supplyAsync(() -> { System.out.println("执行耗时操作..."); timeConsumingOperation(); return 100; }); completableFuture.whenComplete((result, e) -> { System.out.println("结果:" + result); }); System.out.println("主线程运算耗时:" + (System.currentTimeMillis() - l)+ "ms"); new CountDownLatch(1).await(); } catch (Exception e) { e.printStackTrace(); }*/ //回调嵌套:回调的回调 try { long l = System.currentTimeMillis(); CompletableFuture<Integer> completableFuture = CompletableFuture.supplyAsync(() -> { System.out.println("在回调中执行耗时操作..."); timeConsumingOperation(); return 100; }); // 使用 thenCompose 或者 thenComposeAsync 等方法可以实现回调的回调 completableFuture = completableFuture.thenCompose(i -> { return CompletableFuture.supplyAsync(() -> { System.out.println("在回调的回调中执行耗时操作..."); timeConsumingOperation(); return i + 100; }); });//<1> completableFuture.whenComplete((result, e) -> { System.out.println("计算结果:" + result); }); System.out.println("主线程运算耗时:" + (System.currentTimeMillis() - l) + "ms"); new CountDownLatch(1).await(); } catch (Exception e) { e.printStackTrace(); } } // 最常用的同步调用 static int syncCalculate() { System.out.println("执行耗时操作..."); timeConsumingOperation(); return 100; } //耗时操作 static void timeConsumingOperation() { try { Thread.sleep(3000); } catch (Exception e) { e.printStackTrace(); } } }
原博文地址:https://www.cnkirito.moe/future-and-promise/