DefaultEventGateway


1   /*
2    * Copyright (C) 2003  Christian Cryder [christianc@granitepeaks.com]
3    *
4    * This library is free software; you can redistribute it and/or
5    * modify it under the terms of the GNU Lesser General Public
6    * License as published by the Free Software Foundation; either
7    * version 2.1 of the License, or (at your option) any later version.
8    *
9    * This library is distributed in the hope that it will be useful,
10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   * Lesser General Public License for more details.
13   *
14   * You should have received a copy of the GNU Lesser General Public
15   * License along with this library; if not, write to the Free Software
16   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17   *
18   * $Id: DefaultEventGateway.java,v 1.14 2004/02/01 05:16:28 christianc Exp $
19   */
20  package org.enhydra.barracuda.core.event;
21  
22  import java.io.*;
23  import java.util.*;
24  
25  import org.apache.log4j.Logger;
26  
27  import org.enhydra.barracuda.plankton.data.*;
28  
29  /**
30   * Default implementation of an EventGateway. An event
31   * gateway just indicates that the class has an interest in
32   * events, and as such needs access to the EventBroker in 
33   * order to register its listeners there.
34   */
35  public class DefaultEventGateway implements EventGateway {
36  
37      //public constants
38      private static final Logger logger = Logger.getLogger(DefaultEventGateway.class.getName());
39      
40      private static byte[] sep = System.getProperty("line.separator").getBytes();
41  
42      /**
43       * @supplierCardinality 0..* 
44       */
45      private EventGateway parent = null;
46      private List gateways = new ArrayList();
47      private List interests = null;
48      private List aliases = null;
49  
50      /**
51       * Set the parent event gateway. Null indicates its the root.
52       *
53       * @param eg the parent event gateway
54       */
55      public final void setParent(EventGateway eg) {
56          parent = eg;
57      }
58      
59      /**
60       * Get the parent event gateway. Returns null if it's the root.
61       *
62       * @return the parent event gateway
63       */
64      public final EventGateway getParent() {
65          return parent;    
66      }
67      
68      /**
69       * Add an event gateway to this one
70       *
71       * @param eg the event gateway to be added
72       */
73      public final void add(EventGateway eg) {
74          if (eg==null) return;
75          if (logger.isInfoEnabled()) logger.info(this+" adding "+eg);
76          gateways.add(eg);
77          eg.setParent(this);
78      }
79      
80      /**
81       * Remove an event gateway from this one
82       *
83       * @param eg the event gateway to be removed
84       */
85      public final void remove(EventGateway eg) {
86          if (eg==null) return;
87          if (logger.isInfoEnabled()) logger.info(this+" removing "+eg);
88          gateways.remove(eg);
89          eg.setParent(null);
90      }
91      
92      /**
93       * Get a list of child gateways. The list returned is a copy of the
94       * underlying child gateway list.
95       *
96       * @return a list of child gateways
97       */
98      public List getChildren() {
99          return new ArrayList(gateways);
100     }
101 
102     /**
103      * Ask all interested parties to register with
104      * the EventBroker
105      *
106      * @param eb the event broker this gateway should use to 
107      *        register for events
108      */
109     public final void register(EventBroker eb) {
110         if (logger.isInfoEnabled()) logger.info(this+" registering with EventBroker");
111         
112         //register any specified interests
113         if (interests!=null) {
114             Iterator it = interests.iterator();
115             while (it.hasNext()) {
116                 Interest interest = (Interest) it.next();
117                 try {
118                     if (interest.eventClass!=null) eb.addEventListener(interest.factory, interest.eventClass);
119                     else eb.addEventListener(interest.factory);
120                 } catch (org.enhydra.barracuda.core.event.InvalidClassException e) {}
121             }
122         }
123         
124         //register any specified aliases
125         if (aliases!=null) {
126             Iterator it = aliases.iterator();
127             while (it.hasNext()) {
128                 Class   event = (Class  ) it.next();
129                 try {eb.addEventAlias(event);} 
130                 catch (org.enhydra.barracuda.core.event.InvalidClassException e) {}
131             }
132             aliases = null;
133         }
134         
135         //register local interests
136         if (logger.isDebugEnabled()) logger.debug(this+"...registering local interests ");
137         registerLocalEventInterests(eb);
138 
139         //register local aliases        
140         if (logger.isDebugEnabled()) logger.debug(this+"...registering local aliases");
141         registerLocalEventAliases(eb);
142 
143         //register child gateways
144         if (logger.isDebugEnabled()) logger.debug(this+"...registering children ");
145         Iterator it = gateways.iterator();
146         while (it.hasNext()) {
147             EventGateway eg = (EventGateway) it.next();
148             if (logger.isDebugEnabled()) logger.debug(this+"...found child gateway:"+eg);
149             eg.register(eb);
150         }
151 
152         if (logger.isInfoEnabled()) logger.info("Registration complete!");
153     }
154 
155     /**
156      * Register any local interests in the EventBroker
157      *
158      * @param eb the event broker this gateway should use to 
159      *        register for local events
160      */
161     public void registerLocalEventInterests(EventBroker eb) {
162         //this is where users would extend and override
163     }
164 
165     /**
166      * Register any local event aliases in the EventBroker
167      *
168      * @param eb the event broker this gateway should use to 
169      *        register aliases for local events
170      */
171     public void registerLocalEventAliases(EventBroker eb) {
172         //this is where users would extend and override
173     }
174 
175     /**
176      * Rather than overriding the registerLocalEventInterests 
177      * method, you can just invoke this method instead for each 
178      * interest you'd like to register. The gateway will keep track
179      * of all factories specified, and register/deregister when 
180      * appropriate (so you don't have to worry about it). Notice that
181      * this method registers just the listener id (not for a specific
182      * class of event).
183      *
184      * The only real reason for using the registerLocalEventInterests 
185      * method would be if you actually need access to the EventBroker.
186      *
187      * Note that if the event class is not an instance of BaseEvent, the
188      * request is just silently ignored (unlike the event broker, which 
189      * throws an exception).
190      *
191      * @param factory the factory we wish to register with the event broker
192      */
193     public final void specifyLocalEventInterests(ListenerFactory factory) {
194         specifyLocalEventInterests(factory, null);
195     }
196     
197     /**
198      * Rather than overriding the registerLocalEventInterests 
199      * method, you can just invoke this method instead for each 
200      * interest you'd like to register. The gateway will keep track
201      * of all factories specified, and register/deregister when 
202      * appropriate (so you don't have to worry about it). 
203      *
204      * The only real reason for using the registerLocalEventInterests 
205      * method would be if you actually need access to the EventBroker.
206      *
207      * Note that if the event class is not an instance of BaseEvent, the
208      * request is just silently ignored (unlike the event broker, which 
209      * throws an exception).
210      *
211      * @param factory the factory we wish to register with the event broker
212      * @param event the class of events we are interested in
213      */
214     public final void specifyLocalEventInterests(ListenerFactory factory, Class   event) {
215         if (logger.isDebugEnabled()) logger.debug(this+" specifying event interest: "+factory+"-->"+(event!=null ? event.getName() : "null"));
216         if (interests==null) interests = new ArrayList();
217         interests.add(new Interest(factory, event));
218     }
219 
220     /**
221      * Rather than overriding the registerLocalEventAliases 
222      * method, you can just invoke this method instead for type
223      * of event you want to manually alias.
224      *
225      * The only real reason for using the registerLocalEventAliases 
226      * method would be if you actually need access to the EventBroker.
227      *
228      * Note that if the event class is not an instance of BaseEvent, the
229      * request is just silently ignored (unlike the event broker, which 
230      * throws an exception).
231      *
232      * @param event the class of events we are interested in registering 
233      *        aliases for
234      */
235     public final void specifyLocalEventAliases(Class   event) {
236         if (logger.isDebugEnabled()) logger.debug(this+" specifying event alias: "+event.getName());
237         if (aliases==null) aliases = new ArrayList();
238         aliases.add(event);    
239     }
240 
241     /**
242      * Ask all interested parties to de-register with
243      * the EventBroker
244      *
245      * @param eb the event broker this gateway should use to 
246      *        de-register for events
247      */
248     public final void deregister(EventBroker eb) {
249         if (logger.isInfoEnabled()) logger.info(this+" deregistering with EventBroker");
250         
251         //deregister any specified interests
252         if (interests!=null) {
253             Iterator it = interests.iterator();
254             while (it.hasNext()) {
255                 Interest interest = (Interest) it.next();
256                 try {
257                     if (interest.eventClass!=null) eb.removeEventListener(interest.factory, interest.eventClass);
258                     else eb.removeEventListener(interest.factory);
259                 } catch (org.enhydra.barracuda.core.event.InvalidClassException e) {}
260             }
261             interests = null;
262         }
263         
264         //deregister local interests
265         if (logger.isDebugEnabled()) logger.debug(this+"...deregistering local ");
266         deregisterLocalEventInterests(eb);
267         
268         //deregister child gateways
269         if (logger.isDebugEnabled()) logger.debug(this+"...deregistering children ");
270         Iterator it = gateways.iterator();
271         while (it.hasNext()) {
272             EventGateway eg = (EventGateway) it.next();
273             if (logger.isDebugEnabled()) logger.debug(this+"...found child gateway:"+eg);
274             eg.deregister(eb);
275         }
276 
277         if (logger.isInfoEnabled()) logger.info("Deregistration complete!");
278     }
279     
280     /**
281      * Deregister any local interests in the EventBroker
282      *
283      * @param eb the event broker this gateway should use to 
284      *        de-register for local events
285      */
286     public void deregisterLocalEventInterests(EventBroker eb) {
287         //this is where users would extend and override
288     }
289     
290     class Interest {
291         ListenerFactory factory = null;
292         Class   eventClass = null;
293         
294         public Interest(ListenerFactory ifactory, Class   ieventClass) {
295             factory = ifactory;
296             eventClass = ieventClass;        
297         }
298         
299         public String   toString() {
300             return "Interest {factory:"+factory+" event:"+eventClass+"}";
301         }
302     }
303 
304     /**
305      * For debugging purposes. Print the basic structure of the
306      * gateway. 
307      */
308     public void printStackTrace(int depth, Logger extLogger) {
309         printStackTrace(depth, extLogger, null);
310     }
311     
312     /**
313      * For debugging purposes. Print the basic structure of the
314      * gateway. 
315      */
316     public void printStackTrace(int depth, OutputStream out) {
317         printStackTrace(depth, null, out);
318     }
319     
320     /**
321      * For debugging purposes. Print the basic structure of the
322      * gateway. Output is printed to output stream, or if that is null,
323      * to the default logger.
324      */
325     private void printStackTrace(int depth, Logger extLogger, OutputStream out) {
326         if (depth<0) depth = 0;
327         if (depth>25) depth = 25;
328         String   spaces = "                                                                              ";
329         String   inset = spaces.substring(0,depth*3);
330         
331         print(extLogger, out, inset+this.getClass().getName() + "@" + Integer.toHexString(this.hashCode()));            
332 
333         //interests
334         print(extLogger, out, inset+"   interests: "+(interests==null ? "null" : ""));
335         if (interests!=null) CollectionsUtil.printStackTrace(interests, depth+2, extLogger, out);
336         print(extLogger, out, inset+"   /end interests");
337 
338         //aliases
339         print(extLogger, out, inset+"   aliases: "+(aliases==null ? "null" : ""));
340         if (aliases!=null) CollectionsUtil.printStackTrace(aliases, depth+2, extLogger, out);
341         print(extLogger, out, inset+"   /end aliases");
342 
343         //sub-gateways
344         print(extLogger, out, inset+"   gateways: "+(gateways==null ? "null" : ""));
345         int cntr = -1;
346         if (gateways!=null) {
347             Iterator it = gateways.iterator();
348             while (it.hasNext()) {
349                 EventGateway eg = (EventGateway) it.next();
350                 if (eg instanceof DefaultEventGateway) {  
351                     print(extLogger, out, inset+"      ["+(++cntr)+"]:");
352                     ((DefaultEventGateway) eg).printStackTrace(depth+2, extLogger, out);            
353                 } else {
354                     print(extLogger, out, inset+"      ["+(++cntr)+"]"+eg.getClass().getName()+" (details unknown)");
355                 }
356             }                
357         }
358         print(extLogger, out, inset+"   /end gateways");
359 
360         print(extLogger, out, inset+"/end @" + Integer.toHexString(this.hashCode()));
361     }
362 
363     protected static void print(Logger extLogger, OutputStream out, String   s) {
364         if (extLogger!=null) {
365             if (extLogger.isDebugEnabled()) extLogger.debug(s);
366         } else if (out!=null) {
367             try {
368                 out.write(s.getBytes());
369                 out.write(sep);
370             } catch (IOException ioe) {}
371         }
372     }
373 }
374
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