1 引入

比如A在干一件事情，走不开不能中断，此时快递员来送快递，你走不开，只能等做完这件事，再去拿快递，让快递员先放到快递柜。

再比如tomcat中，当Tomcat处理请求到限制，又来请求，处理不了，就会把请求放到一个队列中
等空闲再去处理

2 实现

• 定义一个请求实体

package study.wyy.concurrency.guared;/***  @author: wyaoyao*  @Date: 2020/9/10 9:47 下午*  @Description: 请求*/
public class Request {// 简单模拟请求参数中的属性private String value;public String getValue() {return value;}public void setValue(String value) {this.value = value;}public Request(String value) {this.value = value;}
}

• 定义队列

package study.wyy.concurrency.guared;import java.util.LinkedList;/***  @author: wyaoyao*  @Date: 2020/9/10 9:48 下午*  @Description: 请求队列*/
public class RequestQueue {LinkedList<Request> queue = new LinkedList<>();/***  @author: wyaoyao*  @Date: 2020/9/10 9:41 下午*  @Description: 服务端端通过该方法向队列中get请求*/public Request getRequest(){synchronized (queue){while (queue.size()<=0){// 请求队列中没有请求，那就等着try {queue.wait();} catch (InterruptedException e) {// 当被唤醒的时候，需要break出去，进行工作，比如客户端请求来临的时候return null;}}// 请求队列中有请求数据，那就返回出去return queue.removeFirst();}}/***  @author: wyaoyao*  @Date: 2020/9/10 9:41 下午*  @Description: 客户端通过该方法向队列中提交请求**/public void putRequest(Request request){synchronized (queue){queue.addLast(request);// 唤醒其他线程 起来工作，在get的时候，可能没有请求数据，给wait了，一旦放入请求数据，自然就要唤醒queue.notifyAll();}}}

• client

package study.wyy.concurrency.guared;import java.util.Random;/***  @author: wyaoyao*  @Date: 2020/9/10 9:47 下午*  @Description: 模拟客户端*/
public class ClientThread extends Thread{private final RequestQueue queue;private final Random random;public ClientThread(RequestQueue queue) {this.queue = queue;this.random = new Random(System.currentTimeMillis());}@Overridepublic void run() {for(int i =0;i<10;i++){// 模拟put 请求 10次Request login_request = new Request("login request");System.out.println("client -> request " + login_request.getValue());queue.putRequest(login_request);try {Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {e.printStackTrace();}}}}

• server

package study.wyy.concurrency.guared;import java.util.Objects;
import java.util.Random;public class ServerThread extends Thread{private final RequestQueue queue;private final Random random;/***** 标记：是否关掉*/private volatile Boolean closed = false;public ServerThread(RequestQueue queue) {this.queue = queue;this.random = new Random(System.currentTimeMillis());}@Overridepublic void run() {while (!closed){Request request = queue.getRequest();if(Objects.isNull(request)){// 忽略掉这个为null，这里不能break，那就跳出循环，服务就停了continue;}System.out.println("server -> request " + request.getValue());try {// 模拟处理请求的耗时Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {//e.printStackTrace();// 这里收到中断信号（调用了closed），就return，关闭服务return;}}}/*** @Description 关闭服务* @Author  wyaoyao* @Date   2020/9/10 9:57 下午* @Param* @Return* @Exception*/public void closed(){closed = true;// 这里要打断，因为在get请求的时候可能因为队列中没有请求而wait，是无法判断到这个标记的this.interrupt();System.out.println("server closed");}
}

• 测试

package study.wyy.concurrency.guared;public class Test {public static void main(String[] args) throws InterruptedException {final RequestQueue requestQueue = new RequestQueue();ServerThread serverThread = new ServerThread(requestQueue);serverThread.start();new ClientThread(requestQueue).start();Thread.sleep(10000);serverThread.closed();}
}

client -> request login request
server -> request login request
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server -> request login request
server closed