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这篇文章主要介绍“Java多线程如何使用Guarded Suspension设计模式”,在日常操作中,相信很多人在Java多线程如何使用Guarded Suspension设计模式问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答”Java多线程如何使用Guarded Suspension设计模式”的疑惑有所帮助!接下来,请跟着小编一起来学习吧!
前言:
Guarded Suspension
意为保护暂停,其核心思想是仅当服务进程准备好时,才提供服务。设想一种场景,服务器可能会在很短时间内承受大量的客户端请求,客户端请求的数量可能超过服务器本身的即时处理能力,而服务端程序又不能丢弃任何一个客户请求。此时,最佳的处理方案莫过于让客户端要求进行排队,由服务端程序一个接一个处理。这样,既保证了所有的客户端请求均不丢失,同时也避免了服务器由于同时处理太多的请求而崩溃
Guarded Suspension模式的主要成员有:Request
、RequestQueue
、ClientThread
、 ServerThread
Request
:表示客户端请求
RequestQueue
:用于保存客户端请求队列
ClientThread
:客户端进程
ServerThread
:服务器进程
其中,ClientThread
负责不断发起请求,并将请求对象放入请求队列。ServerThread
则根据其自身的状态,在有能力处理请求时,从RequestQueue
中提取请求对象加以处理。
从流程图中可以看到,客户端的请求数量超过了服务线程的能力。在频繁的客户端请求中,RequestQueue
充当了中间缓存,存放未处理的请求,保证了客户请求不丢失,同时也保护了服务线程不会受到大量并发的请求,而导致计算机资源不足
public class ClientThread extends Thread { private final RequestQueue queue; private final Random random; private final String sendValue; public ClientThread(RequestQueue queue, String sendValue) { this.queue = queue; this.sendValue = sendValue; this.random = new Random(System.currentTimeMillis()); } @Override public void run() { for (int i = 0; i < 10; i++) { System.out.println("Client -> request " + sendValue); queue.putRequest(new Request(sendValue)); try { Thread.sleep(random.nextInt(1000)); } catch (InterruptedException e) { e.printStackTrace(); } } } }
public class Request { private final String value; public Request(String value) { this.value = value; } public String getValue() { return value; } }
public class RequestQueue { private final LinkedList<Request> queue = new LinkedList<>(); public Request getRequest() { synchronized (queue) { while (queue.size() <= 0) { try { queue.wait(); } catch (InterruptedException e) { return null; } } return queue.removeFirst(); } } public void putRequest(Request request) { synchronized (queue) { queue.addLast(request); queue.notifyAll(); } } }
public class ServerThread extends Thread { private final RequestQueue queue; private final Random random; private volatile boolean closed = false; public ServerThread(RequestQueue queue) { this.queue = queue; random = new Random(System.currentTimeMillis()); } @Override public void run() { while (!closed) { Request request = queue.getRequest(); if (null == request) { System.out.println("Received the empty request."); continue; } System.out.println("Server ->" + request.getValue()); try { Thread.sleep(random.nextInt(1000)); } catch (InterruptedException e) { return; } } } public void close() { this.closed = true; this.interrupt(); } }
public class SuspensionClient { public static void main(String[] args) throws InterruptedException { final RequestQueue queue = new RequestQueue(); new ClientThread(queue,"Jack").start(); ServerThread serverThread = new ServerThread(queue); serverThread.start(); Thread.sleep(10000); serverThread.close(); } }
运行:
Client -> request Jack
Server ->Jack
Client -> request Jack
Server ->Jack
Client -> request Jack
Server ->Jack
Client -> request Jack
Server ->Jack
Client -> request Jack
Client -> request Jack
Client -> request Jack
Server ->Jack
Client -> request Jack
Client -> request Jack
Server ->Jack
Client -> request Jack
Server ->Jack
Server ->Jack
Server ->Jack
Server ->Jack
Received the empty request.
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