Netty之io.netty.util.concurrent.Promise与io.netty.util.concurrent.Future初解

目录

目标

Netty版本

Netty官方API

三者之间的关系

基本使用方法

java.util.concurrent.Future

io.netty.util.concurrent.Future

io.netty.util.concurrent.Promise

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目标

• 了解io.netty.util.concurrent.Promise与io.netty.util.concurrent.Future的基本使用方法。
• 了解java.util.concurrent.Future、io.netty.util.concurrent.Promise，io.netty.util.concurrent.Future之间的关系。

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Netty版本

        <dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.87.Final</version></dependency>

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Netty官方API

Netty API Reference (4.1.89.Final)https://netty.io/4.1/api/index.html

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三者之间的关系

区别

• jdk自带的Future只能同步等待结果。
• netty自带的Future能同步等待结果，也可以用异步的方式（如：使用addListener方法设置回调方法）等待结果。
• Promise有Future的所有功能，脱离任务独立存在（可以主动创建并赋结果），只作为线程之间传递结果的容器。

关联

Promise extends netty自带的Future extends jdk自带的Future

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基本使用方法

java.util.concurrent.Future

package com.ctx.netty;import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.*;@Slf4j
public class JavaFuture {public static void main(String[] args) {ExecutorService executor = Executors.newFixedThreadPool(2);Future<String> future = executor.submit(new Callable<String>() {@Overridepublic String call() throws Exception {Thread.sleep(1000);return "result";}});//同步阻塞返回结果。try {log.info("返回结果值：{}",future.get());} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}}
}

io.netty.util.concurrent.Future

package com.ctx.netty;import io.netty.channel.EventLoop;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;
import lombok.extern.slf4j.Slf4j;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;@Slf4j
public class NettyFuture {public static void main(String[] args) {NioEventLoopGroup eventExecutors = new NioEventLoopGroup();EventLoop eventLoop = eventExecutors.next();Future<Map<String, Object>> future = eventLoop.submit(new Callable<Map<String, Object>>() {@Overridepublic Map<String, Object> call() throws Exception {Thread.sleep(1000);Map<String, Object> map = new HashMap<>();map.put("name", "zhangsan");return map;}});new NettyFuture().getNow(future);}/*** 同步阻塞等待结果。* @param future*/public void get(Future<Map<String, Object>> future){try {log.info("结果是："+future.get());} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}}/***异步方式等待结果。* @param future*/public void getNow(Future<Map<String, Object>> future){future.addListener(new GenericFutureListener<Future<? super Map<String, Object>>>() {//拿到结果以后回调方法。所以此时执行get()还是getNow()是一样的效果。@Overridepublic void operationComplete(Future<? super Map<String, Object>> future) throws Exception {log.info("结果是："+future.getNow());}});}
}

io.netty.util.concurrent.Promise

package com.ctx.netty;import io.netty.channel.EventLoop;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.util.concurrent.DefaultPromise;
import io.netty.util.concurrent.Promise;
import lombok.extern.slf4j.Slf4j;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutionException;@Slf4j
public class NettyPromise {public static void main(String[] args) {NioEventLoopGroup eventExecutors = new NioEventLoopGroup();EventLoop eventLoop = eventExecutors.next();//自定义类型，用于填充结果。Promise<Map<String, Object>> promise = new DefaultPromise<>(eventLoop);new Thread(()->{try {Thread.sleep(1000);Map<String, Object> map = new HashMap<>();map.put("name","zhangsan");promise.setSuccess(map);} catch (Exception e) {promise.setFailure(e);}}).start();try {Map<String, Object> map = promise.get();map.forEach((k,v)->{System.out.println(k+"="+v);});} catch (InterruptedException e) {throw new RuntimeException(e);} catch (ExecutionException e) {throw new RuntimeException(e);}}
}