EventPullSource源码分享-优快云博客

本文介绍了一个抽象的事件源类，用于从事件池中拉取事件。包括事件源的启动、停止、激活和去激活方法，以及内部线程的管理。通过抽象方法定义了事件获取和事件睡眠时间的逻辑。

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package
 org.eredlab.g4.rif.pushlet.core; 

import
 org.eredlab.g4.rif.pushlet.util.Log; 
/** 
*
 Abstract Event source from which Events are pulled. 
* 
*
 @author 
*
 @since 2011-05-12 

*/ 

abstract public class EventPullSource implements EventSource, Runnable { 


    private volatile boolean alive = false; 


    private volatile boolean active = false; 


    private static int threadNum = 0; 


    private Thread thread; 


    public EventPullSource() { 


    } 


    abstract protected long getSleepTime(); 


    abstract protected Event pullEvent(); 


    public void start() { 


        thread = new Thread(this, "EventPullSource-" + (++threadNum)); 


        thread.setDaemon(true); 


        thread.start(); 


    } 


    public boolean isAlive() { 


        return alive; 


    } 


    /** 

    * Stop the event generator thread. 


    */ 


    public void stop() { 


        alive = false; 


        if (thread != null) { 


            thread.interrupt(); 


            thread = null; 


        } 


    } 


    /** 

    * Activate the event generator thread. 


    */ 


    synchronized public void activate() { 


        if (active) { 


            return; 


        } 


        active = true; 


        if (!alive) { 


            start(); 


            return; 


        } 


        Log.debug(getClass().getName() + ":
 notifying..."); 


        notifyAll(); 


    } 


    /** 

    * Deactivate the event generator thread. 


    */ 


    public void passivate() { 


        if (!active) { 


            return; 


        } 


        active = false; 


    } 


    /** 

    * Main loop: sleep, generate event and publish. 


    */ 


    public void run() { 


        Log.debug(getClass().getName() + ":
 starting..."); 


        alive = true; 


        while (alive) { 


            try { 


                Thread.sleep(getSleepTime()); 


                // Stopped during sleep: end loop. 


                if (!alive) { 


                    break; 


                } 


                // If passivated wait until we get 


                // get notify()-ied. If there are no subscribers 


                // it wasts CPU to remain producing events... 


                synchronized (this) { 


                    while (!active) { 


                        Log.debug(getClass().getName() + ":
 waiting..."); 


                        wait(); 


                    } 


                } 


            } catch (InterruptedException
 e) { 


                break; 


            } 


            try { 


                // Derived class should produce an event. 


                Event event = pullEvent(); 


                // Let the publisher push it to subscribers. 


                Dispatcher.getInstance().multicast(event); 


            } catch (Throwable
 t) { 


                Log.warn("EventPullSource exception while multicasting ",
 t); 


                t.printStackTrace(); 


            } 


        } 


        Log.debug(getClass().getName() + ":
 stopped"); 


    } 

}