Java多線程之Worker Thread模式
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
會逐個取回工作並進行處理,當所有工作全部完成後,工人線程會等待新的工作到來。
Worker Thread
模式也被成為Background Thread
(背景線程)模式,另外,如果從保存多個工人線程的場所這一點看,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)
創建表示工作請求的Request
並將其傳遞給Channel
。在示例程序中,ClientThread
相當於該角色。
2.Channel(通信線路)
Channel
角色接受來自於Client
的Request
,並將其傳遞給Worker
。在示例程序中,Channel
相當於該角色。
3.Worker(工人)
Worker
角色從Channel
中獲取Request
,並進行工作,當一項工作完成後,它會繼續去獲取另外的Request
,在示例程序中,WorkerThread
相當於該角色。
4.Request(請求)
Request
角色是表示工作的角色,Request
角色中保存瞭進行工作所必須的信息,在示例程序中,Request
相當於該角色。
三.Worker Thread使用場景
想象一個場景,一個工廠在生產玩具,在一個車間裡,有幾個工人,每次生產部件準備好車間外的人就將部件放到車間的一個桌子上,工人每次做完一個玩具就從桌子上取部件。在這裡,註意到,部件並不是直接交給工人的,另外一點,工人並不是做完一個部件就回傢換個新人,後者在現實有點滑稽,但是在程序中卻對應一個典型的線程使用方法:線程池。
所謂線程池,就是對線程的復用,當線程執行完任務之後就繼續取其他任務執行,而不是銷毀啟動新線程執行其他任務。因為線程的啟動對於系統性能開銷比較大,所以這樣對於系統性能的提高很有好處。
四.Worker Thread模式程序示例
首先是請求,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
並且execute
的時候打印出字段的一個簡單類。
ClientThread
,負責將請求放入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
可以當做桌子,是一個數量有限的請求隊列。threadPool
是一個工人線程的數組,這就是一個線程池。在這裡提供瞭putRequest
和takeRequest
方法,分別是往請求隊列放入請求和取出請,這裡使用瞭上一篇博文講到的生產者消費者模式 java
多線程設計模式之消費者生產者模式。確保瞭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(); } } } }
這裡就是一個不斷從請求隊列中取出請求然後執行請求的過程,保證瞭工人線程的復用,並不會執行完一個請求任務就銷毀。
最後是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
省略…
可以看出線程執行任務的線程就是WorkerThread1,2,3,4,5
五個,它們不斷執行來自ClientThread Alex
,Jack
,William
的請求任務。
到此這篇關於Java多線程之Worker Thread
模式的文章就介紹到這瞭,更多相關Java多線程 Worker Thread內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet!
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