java/src/main/com/google/appengine/tools/development/RequestEndListenerHelper.java

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.tools.development;
   4
   5 import com.google.apphosting.api.ApiProxy;
   6 import com.google.apphosting.api.ApiProxy.Environment;
   7
   8 import java.util.Collection;
   9
  10 /**
  11  * Helper class for {@link RequestEndListener}. This class provides two alternate ways to register
  12  * a {@link RequestEndListener}. The first method works with classes that implement a {@link
  13  * RequestEndListener}:
  14  * <blockquote><pre>
  15  *   RequestEndListener listener = ...;
  16  *   RequestEndListenerHelper.register(listener);
  17  * </pre></blockquote>
  18  * The second method is for classes able to extend this class:
  19  * <blockquote><pre>
  20  *   RequestEndListenerHelper listener = ...;
  21  *   listener.register();
  22  * </pre></blockquote>
  23  */
  24 public abstract class RequestEndListenerHelper implements RequestEndListener {
  25   /**
  26    * Register the current instance to be called when a request ends.
  27    */
  28   public void register() {
  29     register(this);
  30   }
  31
  32   /**
  33    * Register a RequestEndListener to be called when a request ends.
  34    *
  35    * @param listener The listener to register.
  36    */
  37   public static void register(RequestEndListener listener) {
  38     getListeners().add(listener);
  39   }
  40
  41   /**
  42    * Get the collection of all the registered RequestEndListeners. The collection is mutable
  43    * so the caller may add or remove listeners
  44    *
  45    * @return The collection of registered RequestEndListeners.
  46    */
  47   public static Collection<RequestEndListener> getListeners() {
  48     Environment environment = ApiProxy.getCurrentEnvironment();
  49     @SuppressWarnings("unchecked")
  50     Collection<RequestEndListener> listenerSet = (Collection<RequestEndListener>)
  51         environment.getAttributes().get(LocalEnvironment.REQUEST_END_LISTENERS);
  52     return listenerSet;
  53   }
  54 }