EventGateway


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: EventGateway.java,v 1.8 2004/02/01 05:16:28 christianc Exp $
19   */
20  package org.enhydra.barracuda.core.event;
21  
22  import java.util.*;
23  
24  /**
25   * An EventGateway simply represents a gateway to a set of event 
26   * handlers within a system. 
27   *
28   * Gateways are heirarchical in that they may contain other 
29   * EventGateways, and may have a parent gateway. Invoking register 
30   * on a gateway should cause it to 
31   *
32   * a) register all known enties that are interested in receiving 
33   *    events from the EventBroker
34   * b) invoke register for any gateways it contains
35   *
36   * Invoking deregister has the opposite effect.
37   */
38  public interface EventGateway {
39  
40      /**
41       * Set the parent event gateway. Null indicates its the root.
42       *
43       * @param eg the parent event gateway
44       */
45      public void setParent(EventGateway eg);
46  
47      /**
48       * Get the parent event gateway. Returns null if it's the root.
49       *
50       * @return the parent event gateway
51       */
52      public EventGateway getParent();
53  
54      /**
55       * Add an event gateway to this one
56       *
57       * @param eg the event gateway to be added
58       */
59      public void add(EventGateway eg);
60  
61      /**
62       * Remove an event gateway from this one
63       *
64       * @param eg the event gateway to be removed
65       */
66      public void remove(EventGateway eg);
67  
68      /**
69       * Get a list of child gateways
70       *
71       * @return a list of child gateways
72       */
73      public List getChildren();
74  
75      /**
76       * Ask all interested parties to register with
77       * the EventBroker
78       *
79       * @param eb the event broker this gateway should use to 
80       *        register for events
81       */
82      public void register(EventBroker eb);
83  
84      /**
85       * Ask all interested parties to de-register with
86       * the EventBroker
87       *
88       * @param eb the event broker this gateway should use to 
89       *        de-register for events
90       */
91      public void deregister(EventBroker eb);
92  
93      /**
94       * Register any local interests in the EventBroker
95       *
96       * @param eb the event broker this gateway should use to 
97       *        register for local events
98       */
99      public void registerLocalEventInterests(EventBroker eb);
100 
101     /**
102      * Deregister any local interests in the EventBroker
103      *
104      * @param eb the event broker this gateway should use to 
105      *        de-register for local events
106      */
107     public void deregisterLocalEventInterests(EventBroker eb);
108 
109     /**
110      * Register any local event aliases in the EventBroker
111      *
112      * @param eb the event broker this gateway should use to 
113      *        register aliases for local events
114      */
115     public void registerLocalEventAliases(EventBroker eb);
116 
117     /**
118      * Rather than overriding the registerLocalEventInterests 
119      * method, you can just invoke this method instead for each 
120      * interest you'd like to register. The gateway will keep track
121      * of all factories specified, and register/deregister when 
122      * appropriate (so you don't have to worry about it). Notice that
123      * this method registers just the listener id (not for a specific
124      * class of event).
125      *
126      * The only real reason for using the registerLocalEventInterests 
127      * method would be if you actually need access to the EventBroker.
128      *
129      * Note that if the event class is not an instance of BaseEvent, the
130      * request is just silently ignored (unlike the event broker, which 
131      * throws an exception).
132      *
133      * @param factory the factory we wish to register with the event broker
134      */
135     public void specifyLocalEventInterests(ListenerFactory factory);
136 
137     /**
138      * Rather than overriding the registerLocalEventInterests 
139      * method, you can just invoke this method instead for each 
140      * interest you'd like to register. The gateway will keep track
141      * of all factories specified, and register/deregister when 
142      * appropriate (so you don't have to worry about it). 
143      *
144      * The only real reason for using the registerLocalEventInterests 
145      * method would be if you actually need access to the EventBroker.
146      *
147      * Note that if the event class is not an instance of BaseEvent, the
148      * request is just silently ignored (unlike the event broker, which 
149      * throws an exception).
150      *
151      * @param factory the factory we wish to register with the event broker
152      * @param event the class of events we are interested in
153      */
154     public void specifyLocalEventInterests(ListenerFactory factory, Class   event);
155 
156     /**
157      * Rather than overriding the registerLocalEventAliases 
158      * method, you can just invoke this method instead for type
159      * of event you want to manually alias.
160      *
161      * The only real reason for using the registerLocalEventAliases 
162      * method would be if you actually need access to the EventBroker.
163      *
164      * Note that if the event class is not an instance of BaseEvent, the
165      * request is just silently ignored (unlike the event broker, which 
166      * throws an exception).
167      *
168      * @param event the class of events we are interested in registering 
169      *        aliases for
170      */
171     public void specifyLocalEventAliases(Class   event);
172 
173 }
174
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