併發程式設計：自定義併發類：自定義非同步流（釋出與訂閱）

目錄

主要內容（參考程式設計流）

一、主程式

二、釋出者(Publisher)

三、釋出任務類（PublisherTask)

四、訂閱實體（ConsumerData)

五、訂閱者（消費者Consumer extends Subscriber）

六、訂閱資訊（Subscription）

七、元素資訊（News）

八、執行結果

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主要內容（參考程式設計流）

• Flow.Publisher:釋出者（提供一個方法來接收Subscriber，進行訊息釋出）
• Flow.Subscriber:訂閱者（提供4個方法，分別用於：訂閱完畢時，出現異常時，新元素被請求時，釋出者註冊訂閱者時。）
• Flow.Subscription:訂閱（提供釋出者與消費者之間的訂閱處理）

一、主程式

1. 實現一個釋出者(Publisher)，兩個消費者(Consumer extends Subscriber)，讓它們建立訂閱關係。
2. 建立元素（News)，由釋出者進行釋出操作（釋出操作會建立獨立的釋出任務，由執行器執行。）

package xyz.jangle.thread.test.n8_xiii.asyncstream;

import java.util.Date;
import java.util.concurrent.TimeUnit;

/**
 * 8.13、自定義非同步流（釋出與訂閱）
 * 
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午3:19:33
 * 
 */
public class M {

	public static void main(String[] args) {
		var publisher = new MyPublisher();
		var consumer1 = new Consumer("Consumer 1");
		var consumer2 = new Consumer("Consumer 2");
		publisher.subscribe(consumer1);
		publisher.subscribe(consumer2);
		System.out.println("M:start");
		var news = new News();
		news.setTitle("My first news");
		news.setContent("This is the content");
		news.setDate(new Date());
		publisher.publish(news);
		try {
			TimeUnit.SECONDS.sleep(1);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		news = new News();
		news.setTitle("My second news");
		news.setContent("This is the content for second news");
		news.setDate(new Date());
		publisher.publish(news);
		System.out.println("M:end");
	}

}

二、釋出者(Publisher)

釋出者包含訂閱者(Subscriber)和訂閱資訊（Subscription）結合的實體（ConsumerData訂閱實體）物件列表。

釋出者包含執行器（ThreadPoolExecutor)，釋出者釋出資訊時，會將元素資訊（News)和訂閱實體構造成釋出任務（PublisherTask），由執行器執行。

package xyz.jangle.thread.test.n8_xiii.asyncstream;

import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.Flow.Publisher;
import java.util.concurrent.Flow.Subscriber;

/**
 * 
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午4:16:54
 * 
 */
public class MyPublisher implements Publisher<News> {

	private ConcurrentLinkedDeque<ConsumerData> consumers;
	private ThreadPoolExecutor executor;

	public MyPublisher() {
		consumers = new ConcurrentLinkedDeque<ConsumerData>();
		executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
	}

	@Override
	public void subscribe(Subscriber<? super News> subscriber) {
		ConsumerData consumerData = new ConsumerData();
		consumerData.setConsumer((Consumer) subscriber);
		var subscription = new MySubscription();
		consumerData.setSubscription(subscription);
		subscriber.onSubscribe(subscription);
		consumers.add(consumerData);
	}
	
	/**
	 *   釋出元素（為每個訂閱者建立一個執行緒並提交給執行器執行。
	 * @param news
	 */
	public void publish(News news) {
		consumers.forEach(consumerData -> {
			try {
				executor.execute(new PublisherTask(consumerData, news));
			} catch (Exception e) {
				consumerData.getConsumer().onError(e);
			}
		});
	}

}

三、釋出任務類（PublisherTask)

package xyz.jangle.thread.test.n8_xiii.asyncstream;

/**
 *  釋出任務類
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午4:07:54
 * 
 */
public class PublisherTask implements Runnable {

	private ConsumerData consumerData;
	private News news;

	public PublisherTask(ConsumerData consumerData, News news) {
		super();
		this.consumerData = consumerData;
		this.news = news;
	}

	@Override
	public void run() {
		MySubscription subscription = consumerData.getSubscription();
		if (!subscription.isCanceled() && subscription.getRequested() > 0) {
			consumerData.getConsumer().onNext(news);
			subscription.decreaseRequested();
		}
	}

}

四、訂閱實體（ConsumerData)

package xyz.jangle.thread.test.n8_xiii.asyncstream;

/**
 *  訂閱者資訊實體
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午4:03:35
 * 
 */
public class ConsumerData {

	private Consumer consumer;
	private MySubscription subscription;

	public Consumer getConsumer() {
		return consumer;
	}

	public void setConsumer(Consumer consumer) {
		this.consumer = consumer;
	}

	public MySubscription getSubscription() {
		return subscription;
	}

	public void setSubscription(MySubscription subscription) {
		this.subscription = subscription;
	}

}

五、訂閱者（消費者Consumer extends Subscriber）

package xyz.jangle.thread.test.n8_xiii.asyncstream;

import java.util.concurrent.Flow.Subscriber;
import java.util.concurrent.Flow.Subscription;

/**
 * 訂閱者（消費者）
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午3:25:14
 * 
 */
public class Consumer implements Subscriber<News> {

	private Subscription subscription;

	private String name;

	public Consumer(String name) {
		super();
		this.name = name;
	}

	@Override
	public void onSubscribe(Subscription subscription) {
		this.subscription = subscription;
		subscription.request(1);
		System.out.println(Thread.currentThread().getName() + ":onSubscribe() ******");
	}

	@Override
	public void onNext(News item) {
		System.out.println(Thread.currentThread().getName() + ":" + name + ":onNext() ******" + item);
		subscription.request(1);

	}

	@Override
	public void onError(Throwable throwable) {
		System.out.println(Thread.currentThread().getName() + ":onError() ******");
	}

	@Override
	public void onComplete() {
		System.out.println(Thread.currentThread().getName() + ":onComplete() ******");
	}

}

六、訂閱資訊（Subscription）

package xyz.jangle.thread.test.n8_xiii.asyncstream;

import java.util.concurrent.Flow.Subscription;

/**
 *  訂閱
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午3:37:50
 * 
 */
public class MySubscription implements Subscription {

	private boolean canceled = false;

	private long requested = 0;

	@Override
	public void request(long n) {
		requested += n;
	}

	@Override
	public void cancel() {
		canceled = true;
	}

	public boolean isCanceled() {
		return canceled;
	}

	public long getRequested() {
		return requested;
	}

	public void decreaseRequested() {
		requested--;
	}

}

七、元素資訊（News）

package xyz.jangle.thread.test.n8_xiii.asyncstream;

import java.util.Date;

/**
 * 元素類
 * 
 * @author jangle
 * @email jangle@jangle.xyz
 * @time 2020年10月16日 下午3:23:03
 * 
 */
public class News {

	private String title, content;

	private Date date;

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getContent() {
		return content;
	}

	public void setContent(String content) {
		this.content = content;
	}

	public Date getDate() {
		return date;
	}

	public void setDate(Date date) {
		this.date = date;
	}

	@Override
	public String toString() {
		return "News [title=" + title + ", content=" + content + ", date=" + date + "]";
	}

}

八、執行結果

main:onSubscribe() ******
main:onSubscribe() ******
M:start
pool-1-thread-1:Consumer 1:onNext() ******News [title=My first news, content=This is the content, date=Fri Oct 16 16:52:44 CST 2020]
pool-1-thread-2:Consumer 2:onNext() ******News [title=My first news, content=This is the content, date=Fri Oct 16 16:52:44 CST 2020]
M:end
pool-1-thread-3:Consumer 1:onNext() ******News [title=My second news, content=This is the content for second news, date=Fri Oct 16 16:52:45 CST 2020]
pool-1-thread-4:Consumer 2:onNext() ******News [title=My second news, content=This is the content for second news, date=Fri Oct 16 16:52:45 CST 2020]