别名
- Thread Pool
- Background Thread
适用的情况
为了提高响应性， 而经常开启新线程让他负责活动的处理，但是每次开启关闭线程都需要花费时间.
实现的方式
在活动的开始就启动多个线程存放起来, 然后将请求发送给这些线程进行处理.这样就不用每次接受请求的时候再进行创建和关闭线程的工作了.
相关的模式
- 在将工人线程的处理结果返回给调用的方法时候， 可以使用Future模式.
- 将请求发送给线程池的缓冲区可以使用Producer-Consumer模式.
代码示例:
示例说明:Channel是请求发送的"管道", Request代表了每个请求, 然后WorkerThread中执行请求的方法.ClientThread模拟了客户端请求的发送.
package com.graphic.workerThread;
public class Channel {
private static final int MAX_REQUEST = 100;
private final Request[] requests;
private int tail;
private int head;
private int count;
private final WorkerThread[] threadPool;
public Channel(int threadNum) {
this.requests = new Request[MAX_REQUEST];
this.threadPool = new WorkerThread[threadNum];
this.head = 0;
this.tail = 0;
this.count = 0;
for (int i = 0; i < threadNum; i++) {
threadPool[i] = new WorkerThread("Worker-" + i, this);
}
}
public void startWorkers() {
for (WorkerThread w :
threadPool) {
w.start();
}
}
public synchronized void putRequest(Request request) {
while (count >= requests.length) {
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
requests[tail] = request;
tail = (tail + 1) % requests.length;
count++;
notifyAll();
}
public synchronized Request takeRequest() {
while (count <= 0) {
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
Request request = requests[head];
head = (head + 1) % requests.length;
count--;
notifyAll();
return request;
}
}
package com.graphic.workerThread;
import java.util.Random;
public class Request {
private final String name;
private final int number;
private static final Random random = new Random();
public Request(String name, int number) {
this.name = name;
this.number = number;
}
public void execute() {
System.out.println(Thread.currentThread().getName() + " execute " + this);
try {
Thread.sleep(random.nextInt(1000));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
public String toString() {
return "[ Request from " + name + " No. " + number + " ]";
}
}
package com.graphic.workerThread;
public class WorkerThread extends Thread {
private final Channel channel;
public WorkerThread(String name, Channel channel) {
super(name);
this.channel = channel;
}
@Override
public void run() {
while (true) {
Request request = channel.takeRequest();
request.execute();
}
}
}
package com.graphic.workerThread;
import java.util.Random;
public class ClientThread extends Thread {
private final Channel channel;
private final Random random = new Random();
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);
channel.putRequest(request);
Thread.sleep(random.nextInt(1000));
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
package com.graphic.workerThread;
public class Main {
public static void main(String[] args) {
Channel channel = new Channel(5);
channel.startWorkers();
new ClientThread("alice", channel).start();
new ClientThread("bob", channel).start();
new ClientThread("blank", channel).start();
}
}
