java高并发系列:google提供的一些好用的并发工具类 | 您所在的位置:网站首页 › java并发处理工具 › java高并发系列:google提供的一些好用的并发工具类 |
java高并发系列:google提供的一些好用的并发工具类
环境:jdk1.8。 关于并发方面的,juc已帮我们提供了很多好用的工具,而谷歌在此基础上做了扩展,使并发编程更容易,这些工具放在guava.jar包中。 本文演示几个简单的案例,见一下guava的效果。 需要先了解的一些技术:juc中的线程池、Excecutors、ExecutorService、Callable、Future guava maven配置 com.google.guava guava 27.0-jre guava中常用几个类 MoreExecutors:提供了一些静态方法,是对juc中的Executors类的一个扩展。Futures:也提供了很多静态方法,是对juc中Future的一个扩展。 案例1:异步执行任务完毕之后回调 package com.itsoku.chat34; import com.google.common.util.concurrent.ListenableFuture; import com.google.common.util.concurrent.ListeningExecutorService; import com.google.common.util.concurrent.MoreExecutors; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; /** 跟着阿里p7学并发,微信公众号:javacode2018 */ @Slf4j public class Demo1 { public static void main(String[] args) throws ExecutionException, InterruptedException { //创建一个线程池 ExecutorService delegate = Executors.newFixedThreadPool(5); try { ListeningExecutorService executorService = MoreExecutors.listeningDecorator(delegate); //异步执行一个任务 ListenableFuture submit = executorService.submit(() -> { log.info("{}", System.currentTimeMillis()); //休眠2秒,默认耗时 TimeUnit.SECONDS.sleep(2); log.info("{}", System.currentTimeMillis()); return 10; }); //当任务执行完毕之后回调对应的方法 submit.addListener(() -> { log.info(“任务执行完毕了,我被回调了”); }, MoreExecutors.directExecutor()); log.info("{}", submit.get()); } finally { delegate.shutdown(); } } } 输出:14:25:50.055 [pool-1-thread-1] INFO com.itsoku.chat34.Demo1 - 1567491950047 14:25:52.063 [pool-1-thread-1] INFO com.itsoku.chat34.Demo1 - 1567491952063 14:25:52.064 [pool-1-thread-1] INFO com.itsoku.chat34.Demo1 - 任务执行完毕了,我被回调了 14:25:52.064 [main] INFO com.itsoku.chat34.Demo1 - 10 说明: ListeningExecutorService接口继承于juc中的ExecutorService接口,对ExecutorService做了一些扩展,看其名字中带有Listening,说明这个接口自带监听的功能,可以监听异步执行任务的结果。通过MoreExecutors.listeningDecorator创建一个ListeningExecutorService对象,需传递一个ExecutorService参数,传递的ExecutorService负责异步执行任务。 ListeningExecutorService的submit方法用来异步执行一个任务,返回ListenableFuture,ListenableFuture接口继承于juc中的Future接口,对Future做了扩展,使其带有监听的功能。调用submit.addListener可以在执行的任务上添加监听器,当任务执行完毕之后会回调这个监听器中的方法。 ListenableFuture的get方法会阻塞当前线程直到任务执行完毕。 上面的还有一种写法,如下: package com.itsoku.chat34; import com.google.common.util.concurrent.*; import lombok.extern.slf4j.Slf4j; import org.checkerframework.checker.nullness.qual.Nullable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; /** 跟着阿里p7学并发,微信公众号:javacode2018 */ @Slf4j public class Demo2 { public static void main(String[] args) throws ExecutionException, InterruptedException { ExecutorService delegate = Executors.newFixedThreadPool(5); try { ListeningExecutorService executorService = MoreExecutors.listeningDecorator(delegate); ListenableFuture submit = executorService.submit(() -> { log.info("{}", System.currentTimeMillis()); TimeUnit.SECONDS.sleep(4); //int i = 10 / 0; log.info("{}", System.currentTimeMillis()); return 10; }); Futures.addCallback(submit, new FutureCallback() { @Override public void onSuccess(@Nullable Integer result) { log.info(“执行成功:{}”, result); } @Override public void onFailure(Throwable t) { try { TimeUnit.MILLISECONDS.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } log.error("执行任务发生异常:" + t.getMessage(), t); } }, MoreExecutors.directExecutor()); log.info("{}", submit.get()); } finally { delegate.shutdown(); }} } 输出: 14:26:07.938 [pool-1-thread-1] INFO com.itsoku.chat34.Demo2 - 1567491967936 14:26:11.944 [pool-1-thread-1] INFO com.itsoku.chat34.Demo2 - 1567491971944 14:26:11.945 [main] INFO com.itsoku.chat34.Demo2 - 10 14:26:11.945 [pool-1-thread-1] INFO com.itsoku.chat34.Demo2 - 执行成功:10 上面通过调用Futures的静态方法addCallback在异步执行的任务中添加回调,回调的对象是一个FutureCallback,此对象有2个方法,任务执行成功调用onSuccess,执行失败调用onFailure。 失败的情况可以将代码中int i = 10 / 0;注释去掉,执行一下可以看看效果。 示例2:获取一批异步任务的执行结果 package com.itsoku.chat34; 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 lombok.extern.slf4j.Slf4j; import java.util.ArrayList; import java.util.List; import java.util.concurrent.*; import java.util.stream.Collectors; /** 跟着阿里p7学并发,微信公众号:javacode2018 */ @Slf4j public class Demo3 { public static void main(String[] args) throws ExecutionException, InterruptedException { log.info(“star”); ExecutorService delegate = Executors.newFixedThreadPool(5); try { ListeningExecutorService executorService = MoreExecutors.listeningDecorator(delegate); List futureList = new ArrayList(); for (int i = 5; i >= 0; i–) { int j = i; futureList.add(executorService.submit(() -> { TimeUnit.SECONDS.sleep(j); return j; })); } //获取一批任务的执行结果 List resultList = Futures.allAsList(futureList).get(); //输出 resultList.forEach(item -> { log.info("{}", item); }); } finally { delegate.shutdown(); } } } 输出:14:26:35.970 [main] INFO com.itsoku.chat34.Demo3 - star 14:26:41.137 [main] INFO com.itsoku.chat34.Demo3 - 5 14:26:41.138 [main] INFO com.itsoku.chat34.Demo3 - 4 14:26:41.138 [main] INFO com.itsoku.chat34.Demo3 - 3 14:26:41.138 [main] INFO com.itsoku.chat34.Demo3 - 2 14:26:41.138 [main] INFO com.itsoku.chat34.Demo3 - 1 14:26:41.138 [main] INFO com.itsoku.chat34.Demo3 - 0 结果中按顺序输出了6个异步任务的结果,此处用到了Futures.allAsList方法,看一下此方法的声明: public static ListenableFuture allAsList( Iterable |
CopyRight 2018-2019 实验室设备网 版权所有 |