Worker Thread设计模式

Worker Thread模式的基本思路是，有一个流水线（channel），客户端不断的把任务（request）放到其中，当有任务时，工作线程（worker）就执行任务，否则等待任务。
下面对这个模式简单实现

首先定义request类

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() + " execute Request" + this.name + ", number is " + number);    }}

Request类有name和number属性。还有一个execute方法，决定了worker怎么去执行任务。

定义channel类

public class Channel {    private final int MAX_SIZE = 100;    private final Request[] requests;    private int head;    private int tail;    private int count;    private final Worker[] workers;    public Channel(int workers) {        this.requests = new Request[MAX_SIZE];        this.head = 0;        this.tail = 0;        this.count = 0;        this.workers = new Worker[workers];        init();    }    private void init() {        for (int i = 0; i < workers.length; i++) {            workers[i] = new Worker("Worker-" + i, this);        }    }    public void startWorkers() {        Arrays.asList(workers).forEach(Worker::start);    }    public synchronized void put(Request request) {        while (count >= requests.length) {            try {                this.wait();            } catch (InterruptedException e) {                e.printStackTrace();            }        }        requests[tail] = request;        tail = (tail + 1) % requests.length;        count++;        this.notifyAll();    }    public synchronized Request take() {        while (count <= 0) {            try {                this.wait();            } catch (InterruptedException e) {                e.printStackTrace();            }        }        Request request = requests[head];        head = (head + 1) % requests.length;        count--;        this.notifyAll();        return request;    }}

定义了一个队列，包含了任务和执行任务的worker，并在构造函数中初始化worker。还有put和take方法，用于向对类中放和取任务。put方法将任务放到队尾，take方法将任务放到对头。

定义worker

public class Worker extends Thread {    private Channel channel;    private static final Random random = new Random(System.currentTimeMillis());    public Worker(String name, Channel channel) {        super(name);        this.channel = channel;    }    @Override    public void run() {        while (true) {            Request request = channel.take();            request.execute();            try {                Thread.sleep(random.nextInt(1000));            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}

worker继承thread，其任务就是不断的从channel的队列中获取request并执行

模拟向channel中不断放入任务

public class Transport extends Thread {    private final Channel channel;    private static final Random random = new Random(System.currentTimeMillis());    public Transport(String name, Channel channel) {        super(name);        this.channel = channel;    }    @Override    public void run() {        for (int i = 0; true; i++) {            Request request = new Request(getName(), i);            channel.put(request);            try {                Thread.sleep(random.nextInt(1000));            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}

不断构造request放入channel

测试

public class Client {    public static void main(String[] args) {        final Channel channel = new Channel(5);        channel.startWorkers();        new Transport("t1", channel).start();        new Transport("t2", channel).start();        new Transport("t3", channel).start();    }}

结果

Worker-3 execute Requestt2, number is 0Worker-2 execute Requestt3, number is 0Worker-4 execute Requestt1, number is 0Worker-0 execute Requestt2, number is 1Worker-1 execute Requestt2, number is 2Worker-4 execute Requestt2, number is 3Worker-0 execute Requestt2, number is 4Worker-2 execute Requestt3, number is 1Worker-3 execute Requestt1, number is 1Worker-0 execute Requestt3, number is 2Worker-1 execute Requestt1, number is 2Worker-2 execute Requestt2, number is 5Worker-4 execute Requestt2, number is 6Worker-4 execute Requestt3, number is 3Worker-3 execute Requestt3, number is 4Worker-2 execute Requestt3, number is 5Worker-2 execute Requestt1, number is 3Worker-1 execute Requestt2, number is 7Worker-0 execute Requestt3, number is 6Worker-1 execute Requestt2, number is 8Worker-3 execute Requestt3, number is 7Worker-4 execute Requestt1, number is 4Worker-1 execute Requestt2, number is 9Worker-0 execute Requestt1, number is 5Worker-3 execute Requestt3, number is 8Worker-4 execute Requestt3, number is 9Worker-3 execute Requestt1, number is 6Worker-0 execute Requestt3, number is 10Worker-2 execute Requestt2, number is 10Worker-1 execute Requestt2, number is 11Worker-2 execute Requestt1, number is 7Worker-4 execute Requestt2, number is 12Worker-2 execute Requestt1, number is 8Worker-3 execute Requestt3, number is 11Worker-3 execute Requestt2, number is 13Worker-4 execute Requestt2, number is 14Worker-1 execute Requestt2, number is 15...