ListenerSupport


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87  package org.codehaus.loom.components.application;
88  
89  import org.apache.avalon.phoenix.ApplicationEvent;
90  import org.apache.avalon.phoenix.ApplicationListener;
91  import org.apache.avalon.phoenix.BlockEvent;
92  import org.apache.avalon.phoenix.BlockListener;
93  import org.apache.avalon.phoenix.metadata.SarMetaData;
94  import org.apache.avalon.phoenix.metainfo.BlockInfo;
95  import org.codehaus.loom.components.util.ComponentInfoConverter;
96  
97  /**
98   * Manage a set of {@link ApplicationListener} objects and propogate {@link
99   * ApplicationEvent} notifications to these listeners.  Not all events pass an
100  * Applicationevent parameter.
101  *
102  * @author Peter Donald
103  * @author <a HREF="mailto:Paul_Hammant@yahoo.com">Paul Hammant</a>
104  */
105 final class ListenerSupport
106 {
107     //Set of block listeners. Must be accessed from synchronized code
108     private BlockListener[] m_blockListeners = new BlockListener[ 0 ];
109 
110     //Set of listeners. Must be accessed from synchronized code
111     private ApplicationListener[] m_listeners = new ApplicationListener[ 0 ];
112 
113     /**
114      * fire Event indicating that the Application represented by specified
115      * metaData is starting.
116      *
117      * @param metaData the metaData
118      */
119     void fireApplicationStartingEvent( final SarMetaData metaData )
120         throws Exception  
121     {
122         final ApplicationEvent event =
123             new ApplicationEvent( metaData.getName(), metaData );
124         applicationStarting( event );
125     }
126 
127     /**
128      * fire Event indicating that Block represented by specific entry has been
129      * added.
130      *
131      * @param entry the entry
132      */
133     void fireBlockAddedEvent( final BlockEntry entry )
134     {
135         blockAdded( createEvent( entry ) );
136     }
137 
138     /**
139      * fire Event indicating that Block represented by specific entry is being
140      * removed.
141      *
142      * @param entry the entry
143      */
144     void fireBlockRemovedEvent( final BlockEntry entry )
145     {
146         blockRemoved( createEvent( entry ) );
147     }
148 
149     /**
150      * Utility method to create an event for a specific entry.
151      *
152      * @param entry the entry
153      * @return the new event
154      */
155     private BlockEvent createEvent( final BlockEntry entry )
156     {
157         final BlockInfo blockInfo =
158             ComponentInfoConverter.toBlockInfo( entry.getInfo() );
159         return new BlockEvent( entry.getName(),
160                                entry.getProxy(),
161                                blockInfo );
162     }
163 
164     /**
165      * Add a ApplicationListener to those requiring notification of {@link
166      * ApplicationEvent}s.
167      *
168      * @param listener the ApplicationListener
169      */
170     public synchronized void addApplicationListener(
171         final ApplicationListener listener )
172     {
173         final ApplicationListener[] listeners = new ApplicationListener[ 1 +
174             m_listeners.length ];
175         System.arraycopy( m_listeners, 0, listeners, 0, m_listeners.length );
176         listeners[ m_listeners.length ] = listener;
177         m_listeners = listeners;
178     }
179 
180     /**
181      * Remove a ApplicationListener from those requiring notification of {@link
182      * ApplicationEvent}s.
183      *
184      * @param listener the ApplicationListener
185      */
186     public synchronized void removeApplicationListener(
187         final ApplicationListener listener )
188     {
189         int index = 0;
190         while( index < m_listeners.length )
191         {
192             if( m_listeners[ index ] == listener )
193             {
194                 break;
195             }
196             index++;
197         }
198 
199         if( m_listeners.length != index )
200         {
201             final ApplicationListener[] listeners =
202                 new ApplicationListener[ m_listeners.length - 1 ];
203             System.arraycopy( m_listeners, 0, listeners, 0, index );
204             final int length = m_listeners.length - index - 1;
205             System.arraycopy( m_listeners,
206                               index + 1,
207                               listeners,
208                               index,
209                               length );
210         }
211     }
212 
213     /**
214      * Add a BlockListener to those requiring notification of {@link
215      * BlockEvent}s.
216      *
217      * @param listener the BlockListener
218      */
219     public synchronized void addBlockListener( final BlockListener listener )
220     {
221         final BlockListener[] listeners = new BlockListener[ 1 +
222             m_blockListeners.length ];
223         System.arraycopy( m_blockListeners,
224                           0,
225                           listeners,
226                           0,
227                           m_blockListeners.length );
228         listeners[ m_listeners.length ] = listener;
229         m_blockListeners = listeners;
230     }
231 
232     /**
233      * Remove a BlockListener from those requiring notification of {@link
234      * BlockEvent}s.
235      *
236      * @param listener the BlockListener
237      */
238     public synchronized void removeBlockListener( final BlockListener listener )
239     {
240         int index = 0;
241         while( index < m_blockListeners.length )
242         {
243             if( m_blockListeners[ index ] == listener )
244             {
245                 break;
246             }
247             index++;
248         }
249 
250         if( m_blockListeners.length != index )
251         {
252             final BlockListener[] listeners =
253                 new BlockListener[ m_blockListeners.length - 1 ];
254             System.arraycopy( m_blockListeners, 0, listeners, 0, index );
255             final int length = m_blockListeners.length - index - 1;
256             System.arraycopy( m_blockListeners,
257                               index + 1,
258                               listeners,
259                               index,
260                               length );
261         }
262     }
263 
264     /**
265      * Notification that the application is starting
266      *
267      * @param event the ApplicationEvent
268      */
269     private synchronized void applicationStarting(
270         final ApplicationEvent event )
271         throws Exception  
272     {
273         for( int i = 0; i < m_listeners.length; i++ )
274         {
275             m_listeners[ i ].applicationStarting( event );
276         }
277     }
278 
279     /**
280      * Notification that the application has started.
281      */
282     public synchronized void applicationStarted()
283     {
284         for( int i = 0; i < m_listeners.length; i++ )
285         {
286             m_listeners[ i ].applicationStarted();
287         }
288     }
289 
290     /**
291      * Notification that the application is stopping
292      */
293     public synchronized void applicationStopping()
294     {
295         for( int i = 0; i < m_listeners.length; i++ )
296         {
297             m_listeners[ i ].applicationStopping();
298         }
299     }
300 
301     /**
302      * Notification that the application has stopped
303      */
304     public synchronized void applicationStopped()
305     {
306         for( int i = 0; i < m_listeners.length; i++ )
307         {
308             m_listeners[ i ].applicationStopped();
309         }
310     }
311 
312     /**
313      * Notification that the application has failed
314      */
315     public synchronized void applicationFailure(
316         final Exception   causeOfFailure )
317     {
318         for( int i = 0; i < m_listeners.length; i++ )
319         {
320             m_listeners[ i ].applicationFailure( causeOfFailure );
321         }
322     }
323 
324     /**
325      * Notification that a block has just been added to Server Application.
326      *
327      * @param event the BlockEvent
328      */
329     private synchronized void blockAdded( final BlockEvent event )
330     {
331         for( int i = 0; i < m_listeners.length; i++ )
332         {
333             m_listeners[ i ].blockAdded( event );
334         }
335 
336         //Now notify the plain BlockListeners
337         for( int i = 0; i < m_blockListeners.length; i++ )
338         {
339             m_blockListeners[ i ].blockAdded( event );
340         }
341     }
342 
343     /**
344      * Notification that a block is just about to be removed from Server
345      * Application.
346      *
347      * @param event the BlockEvent
348      */
349     private synchronized void blockRemoved( final BlockEvent event )
350     {
351         for( int i = 0; i < m_listeners.length; i++ )
352         {
353             m_listeners[ i ].blockRemoved( event );
354         }
355 
356         //Now notify the plain BlockListeners
357         for( int i = 0; i < m_blockListeners.length; i++ )
358         {
359             m_blockListeners[ i ].blockRemoved( event );
360         }
361     }
362 }
363
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