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Java多線程之Worker Thread模式

更新時(shí)間：2021年10月28日 16:32:32 作者：冬日毛毛雨

這篇文章主要介紹了Java多線程之Worker Thread模式，Worker的意思是工作的人，在Worker Thread模式中，工人線程Worker thread會(huì)逐個(gè)取回工作并進(jìn)行處理，當(dāng)所有工作全部完成后，工人線程會(huì)等待新的工作到來(lái)，下面文章小編回給大家詳細(xì)介紹,需要的朋友可以參考一下

一.Worker Thread模式

Worker的意思是工作的人，在Worker Thread模式中，工人線程Worker thread會(huì)逐個(gè)取回工作并進(jìn)行處理，當(dāng)所有工作全部完成后，工人線程會(huì)等待新的工作到來(lái)。

Worker Thread模式也被成為Background Thread（背景線程）模式，另外，如果從保存多個(gè)工人線程的場(chǎng)所這一點(diǎn)看，我們也可以稱這種模式為Thread Pool模式。

二 .Worker Thread模式中的角色

1.Client（委托者）

創(chuàng)建表示工作請(qǐng)求的Request并將其傳遞給Channel。在示例程序中，ClientThread相當(dāng)于該角色。

2.Channel（通信線路）

Channel角色接受來(lái)自于Client的Request，并將其傳遞給Worker。在示例程序中，Channel相當(dāng)于該角色。

3.Worker（工人）

Worker角色從Channel中獲取Request，并進(jìn)行工作，當(dāng)一項(xiàng)工作完成后，它會(huì)繼續(xù)去獲取另外的Request，在示例程序中，WorkerThread相當(dāng)于該角色。

4.Request（請(qǐng)求）

Request角色是表示工作的角色，Request角色中保存了進(jìn)行工作所必須的信息，在示例程序中，Request相當(dāng)于該角色。

三.Worker Thread使用場(chǎng)景

想象一個(gè)場(chǎng)景，一個(gè)工廠在生產(chǎn)玩具，在一個(gè)車間里，有幾個(gè)工人，每次生產(chǎn)部件準(zhǔn)備好車間外的人就將部件放到車間的一個(gè)桌子上，工人每次做完一個(gè)玩具就從桌子上取部件。在這里，注意到，部件并不是直接交給工人的，另外一點(diǎn)，工人并不是做完一個(gè)部件就回家換個(gè)新人，后者在現(xiàn)實(shí)有點(diǎn)滑稽，但是在程序中卻對(duì)應(yīng)一個(gè)典型的線程使用方法：線程池。

所謂線程池，就是對(duì)線程的復(fù)用，當(dāng)線程執(zhí)行完任務(wù)之后就繼續(xù)取其他任務(wù)執(zhí)行，而不是銷毀啟動(dòng)新線程執(zhí)行其他任務(wù)。因?yàn)榫€程的啟動(dòng)對(duì)于系統(tǒng)性能開(kāi)銷比較大，所以這樣對(duì)于系統(tǒng)性能的提高很有好處。

四.Worker Thread模式程序示例

首先是請(qǐng)求，即玩具的部件

public class Request {

    private final String name;
    private final int number;

    public Request(String name, int number) {
        this.name = name;
        this.number = number;
    }

    public void execute(){
        System.out.println(Thread.currentThread().getName()+" executed "+this);
    }
    @Override
    public String toString() {
        return "Request=> " + "No." + number + "  Name." + name;
    }
}

也就是擁有name和number并且execute的時(shí)候打印出字段的一個(gè)簡(jiǎn)單類。

ClientThread，負(fù)責(zé)將請(qǐng)求放入RequestQueue中，即將部件放到桌子上。

public class ClientThread extends Thread {

    private static final Random random = new Random(System.currentTimeMillis());

    private final Channel channel;

    public ClientThread(String name, Channel channel) {
        super(name);
        this.channel = channel;
    }

    @Override
    public void run() {
        try {

            for (int i = 0; true; i++) {
                Request request = new Request(getName(),i);
                this.channel.put(request);
                Thread.sleep(random.nextInt(1_000));
            }
        } catch (Exception e) {

        }
    }
}

Channel類，可以當(dāng)做車間

public class Channel {

    private final static int MAX_REQUEST = 100;

    private final Request[] requestQueue;
    private final WorkerThread[] workerPool;
    private int head;
    private int tail;
    private int count;

    public Channel(int workers) {

        this.requestQueue = new Request[MAX_REQUEST];
        this.head = 0;
        this.tail = 0;
        this.count = 0;
        this.workerPool = new WorkerThread[workers];
        this.init();
    }

    private void init() {
        for (int i = 0; i < workerPool.length; i++) {
            workerPool[i] = new WorkerThread("Worker-" + i, this);
        }
    }

    /**
     * push switch to start all of worker to work
     */
    public void startWorker() {
        Arrays.asList(workerPool).forEach(WorkerThread::start);

//        List<WorkerThread> workerThreads = Arrays.asList(workerPool);
//
//        workerThreads.stream().forEach(WorkerThread::start);
    }

    public synchronized void put(Request request) {
        while (count >= requestQueue.length) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        this.requestQueue[tail] = request;
        this.tail = (tail + 1) % requestQueue.length;
        this.count++;
        this.notifyAll();
    }

    public synchronized Request take() {
        while (count <= 0) {
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        Request request = this.requestQueue[head];
        this.head = (this.head + 1) % this.requestQueue.length;
        this.count--;
        this.notifyAll();
        return request;
    }
}

Requestqueue可以當(dāng)做桌子，是一個(gè)數(shù)量有限的請(qǐng)求隊(duì)列。threadPool是一個(gè)工人線程的數(shù)組，這就是一個(gè)線程池。在這里提供了putRequest和takeRequest方法，分別是往請(qǐng)求隊(duì)列放入請(qǐng)求和取出請(qǐng)，這里使用了上一篇博文講到的生產(chǎn)者消費(fèi)者模式 java多線程設(shè)計(jì)模式之消費(fèi)者生產(chǎn)者模式。確保了WorkerThread和ClientThread之間可以友好合作。

工人線程：

public class WorkerThread extends Thread {

    private static final Random random = new Random(System.currentTimeMillis());
    private final Channel channel;

    public WorkerThread(String name, Channel channel) {
        super(name);
        this.channel = channel;
    }

    @Override
    public void run() {
        while (true) {
            channel.take().execute();

            try {
                Thread.sleep(random.nextInt(1_000));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

這里就是一個(gè)不斷從請(qǐng)求隊(duì)列中取出請(qǐng)求然后執(zhí)行請(qǐng)求的過(guò)程，保證了工人線程的復(fù)用，并不會(huì)執(zhí)行完一個(gè)請(qǐng)求任務(wù)就銷毀。

最后是Main：

public class WorkerClient {

    public static void main(String[] args) {
        final Channel channel = new Channel(5);
        channel.startWorker();

        new ClientThread("Alex", channel).start();
        new ClientThread("Jack", channel).start();
        new ClientThread("William", channel).start();
    }
}

結(jié)果：

Worker-4 executed Request=> No.0 Name.Alex
Worker-2 executed Request=> No.0 Name.Jack
Worker-3 executed Request=> No.0 Name.William
Worker-4 executed Request=> No.1 Name.Jack
Worker-0 executed Request=> No.1 Name.William
Worker-3 executed Request=> No.2 Name.Jack
Worker-2 executed Request=> No.1 Name.Alex
Worker-4 executed Request=> No.2 Name.William
Worker-1 executed Request=> No.3 Name.Jack
Worker-3 executed Request=> No.2 Name.Alex
Worker-4 executed Request=> No.3 Name.William
Worker-0 executed Request=> No.4 Name.Jack
Worker-0 executed Request=> No.3 Name.Alex
Worker-1 executed Request=> No.5 Name.Jack
Worker-3 executed Request=> No.4 Name.William
Worker-1 executed Request=> No.6 Name.Jack
Worker-2 executed Request=> No.4 Name.Alex
Worker-3 executed Request=> No.7 Name.Jack
Worker-0 executed Request=> No.5 Name.William
Worker-1 executed Request=> No.5 Name.Alex
Worker-4 executed Request=> No.8 Name.Jack
Worker-2 executed Request=> No.6 Name.Alex
Worker-0 executed Request=> No.7 Name.Alex
Worker-4 executed Request=> No.8 Name.Alex
Worker-2 executed Request=> No.6 Name.William
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