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Java > Open Source Codes > com > db4o > events > EventRegistryFactory


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.events;
22
23 import com.db4o.ObjectContainer;
24 import com.db4o.YapStream;
25 import com.db4o.events.impl.EventRegistryImpl;
26 import com.db4o.foundation.ArgumentNullException;
27 import com.db4o.inside.callbacks.Callbacks;
28 import com.db4o.inside.callbacks.NullCallbacks;
29
30 /**
31  * Provides an interface for getting an {@link EventRegistry} from an {@link ObjectContainer}.
32  */
33 public class EventRegistryFactory {
34     
35     /**
36      * Returns an {@link EventRegistry} for registering events with the specified container.
37      */
38     public static EventRegistry forObjectContainer(ObjectContainer container) {
39         if (null == container) {
40             throw new ArgumentNullException("container");
41         }
42         
43         YapStream stream = ((YapStream)container);
44         Callbacks callbacks = stream.callbacks();
45         if (callbacks instanceof EventRegistry) {
46             return (EventRegistry)callbacks;
47         }
48         if (callbacks instanceof NullCallbacks) {
49             EventRegistryImpl impl = new EventRegistryImpl();
50             stream.callbacks(impl);
51             return impl;
52         }
53         
54         // TODO: create a MulticastingCallbacks and register both
55 // the current one and the new one
56 throw new IllegalArgumentException JavaDoc("container callbacks already in use");
57     }
58 }
59
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