java多线程之Active Object模式

一、Active Object模式-接收异步消息的主动对象

Active是主动的意思，因此ActiveObject就是主动对象的意思。所谓主动一般指有自己特有的线程，举例来说，java.lang.Thread类的实例就是一种主动对象。

不过，在Active Object模式中出厂的主动对象可不仅仅有自己特有的线程，它同时还具备可以从外部接收和处理异步消息并根据需要返回处理结果的特征。

Active Object模式中的主动对象会通过自己特有的线程在合适的时机处理从外部接收到的异步消息。

在Active Object中，组成主动对象与许多自然人组成法人类似，即使是java语言这样没有异步消息的编程语言，也可以使用Active Object模式组成实际上能够处理异步消息的主动对象。

二、示例程序

将通过示例程序实现“生成字符串”和“显示字符串”这二种功能的主动对象。

1.示例程序类和接口一览表

类名说明Main.java测试示例程序的类MakerClientThread.java发出“生成字符串”请求的线程DisplayClientThread.java发出“显示字符串”请求的线程ActiveObject.java定义“主动对象”的接口（API）的接口ActiveObjectFactory.java创建“主动对象”的类Proxy.java将方法调用转换为MethodRequest对象的类（实现了ActiveObject的接口）SchedulerThread.java调用execute方法处理 MethodRequest对象的类ActivationQueue.java按顺序保存MethodRequest对象的类MethodRequest.java表示请求的抽象类MakeStringRequest.javamakeString方法（生成字符串）对应的类，MethodRequest类的子类DisplayStringRequest.javadisplayString方法（显示字符串）对应的类，MethodRequest类的子类Result.java表示执行结果的抽象类FutureResult.java在Future模式中表示执行结果的类RealResult.java表示实际的执行结果的类Servant.java执行实际处理的类（实现了ActiveObject接口）

2.示例程序的类图

3.示例程序时序图

4.Main类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public class Main {

public static void main(String[] args) {

ActiveObject activeObject = ActiveObjectFactory.createActiveObject();

new MakerClientThread("Steve Nash", activeObject).start();

new MakerClientThread("Michael Jordan", activeObject).start();

new DisplayClientThread("Ronaldo", activeObject).start();

}

}

5.MakerClientThread类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public class MakerClientThread extends Thread {

private final ActiveObject activeObject;

private final char fillchar;

public MakerClientThread(String name, ActiveObject activeObject) {

super(name);

this.activeObject = activeObject;

this.fillchar = name.charAt(0);

}

public void run() {

try {

for (int i = 0; true; i++) {

//有返回值的调用

Result result = activeObject.makeString(i, fillchar);

Thread.sleep(10);

String value = result.getResultValue();

System.out.println(Thread.currentThread().getName() + ": value = " + value);

}

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

6.DisplayClientThread类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public class DisplayClientThread extends Thread {

private final ActiveObject activeObject;

public DisplayClientThread(String name, ActiveObject activeObject) {

super(name);

this.activeObject = activeObject;

}

public void run() {

try {

for (int i = 0; true; i++) {

//没有返回值的调用

String string = Thread.currentThread().getName() + " " + i;

activeObject.displayString(string);

Thread.sleep(200);

}

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

7.ActiveObject类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public interface ActiveObject {

public abstract Result makeString(int count, char fillchar);

public abstract void displayString(String string);

}

8.ActiveObjectFactory类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public class ActiveObjectFactory {

public static ActiveObject createActiveObject() {

Servant servant = new Servant();

ActivationQueue queue = new ActivationQueue();

SchedulerThread scheduler = new SchedulerThread(queue);

Proxy proxy = new Proxy(scheduler, servant);

scheduler.start();

return proxy;

}

}

9.Proxy类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public class Proxy implements ActiveObject {

private final SchedulerThread scheduler;

private final Servant servant;

public Proxy(SchedulerThread scheduler, Servant servant) {

this.scheduler = scheduler;

this.servant = servant;

}

@Override

public Result makeString(int count, char fillchar) {

FutureResult future = new FutureResult();

scheduler.invoke(new MakeStringRequest(servant, future, count, fillchar));

return future;

}

@Override

public void displayString(String string) {

scheduler.invoke(new DisplayStringRequest(servant, string));

}

}

10.SchedulerThread类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:35

* @Description:

*/

public class SchedulerThread extends Thread {

private final ActivationQueue queue;

public SchedulerThread(ActivationQueue queue) {

this.queue = queue;

}

public void invoke(MethodRequest request) {

queue.putRequest(request);

}

public void run() {

while (true) {

MethodRequest request = queue.takeRequest();

request.execute();

}

}

}

11.ActivationQueue类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:37

* @Description:

*/

public class ActivationQueue {

private static final int MAC_METHOD_REQUEST = 100;

private final MethodRequest[] requestQueue;

private int tail; //下次putRqueset的位置

private int head; //下次takeRequest的位置

private int count; //MethodRequest的数量

public ActivationQueue() {

this.requestQueue = new MethodRequest[MAC_METHOD_REQUEST];

this.head = 0;

this.tail = 0;

this.count = 0;

}

public synchronized void putRequest(MethodRequest request) {

while (count >= requestQueue.length) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

requestQueue[tail] = request;

tail = (tail + 1) % requestQueue.length;

count++;

notifyAll();

}

public synchronized MethodRequest takeRequest() {

while (count <= 0) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

MethodRequest request = requestQueue[head];

head = (head + 1) % requestQueue.length;

count--;

notifyAll();

return request;

}

}

12.MethodRequest类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:37

* @Description:

*/

abstract class MethodRequest {

protected final Servant servant;

protected final FutureResult future;

protected MethodRequest(Servant servant, FutureResult future) {

this.servant = servant;

this.future = future;

}

public abstract void execute();

}

13.MakeStringRequest类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:38

* @Description:

*/

public class MakeStringRequest extends MethodRequest {

private final int count;

private final char fillchar;

public MakeStringRequest(Servant servant, FutureResult future, int count, char fillchar) {

super(servant, future);

this.count = count;

this.fillchar = fillchar;

}

public void execute() {

Result result = servant.makeString(count, fillchar);

future.setResult(result);

}

}

14.DisplayStringRequest类

package com.viagra.Active_Object_Pattern.Lesson1;

/**

* @Auther: viagra

* @Date: 2019/11/19 20:38

* @Description:

*/

public class DisplayStringRequest extends MethodRequest