EventPullSource源码分享-优快云博客

 
  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");  
  }  
 }