01: /*
02: * Consumer.java
03: *
04: * Version: $Revision: 2074 $
05: *
06: * Date: $Date: 2007-07-19 14:40:11 -0500 (Thu, 19 Jul 2007) $
07: *
08: * Copyright (c) 2002-2007, Hewlett-Packard Company and Massachusetts
09: * Institute of Technology. All rights reserved.
10: *
11: * Redistribution and use in source and binary forms, with or without
12: * modification, are permitted provided that the following conditions are
13: * met:
14: *
15: * - Redistributions of source code must retain the above copyright
16: * notice, this list of conditions and the following disclaimer.
17: *
18: * - Redistributions in binary form must reproduce the above copyright
19: * notice, this list of conditions and the following disclaimer in the
20: * documentation and/or other materials provided with the distribution.
21: *
22: * - Neither the name of the Hewlett-Packard Company nor the name of the
23: * Massachusetts Institute of Technology nor the names of their
24: * contributors may be used to endorse or promote products derived from
25: * this software without specific prior written permission.
26: *
27: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28: * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29: * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
30: * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31: * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
32: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
33: * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
34: * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
35: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
36: * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
37: * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
38: * DAMAGE.
39: */
40:
41: package org.dspace.event;
42:
43: import org.dspace.core.Context;
44:
45: /**
46: * Interface for content event consumers. Note that the consumer cannot tell if
47: * it is invoked synchronously or asynchronously; the consumer interface and
48: * sequence of calls is the same for both. Asynchronous consumers may see more
49: * consume() calls between the start and end of the event stream, if they are
50: * invoked asynchronously, once in a long time period, rather than synchronously
51: * after every Context.commit().
52: *
53: * @version $Revision: 2074 $
54: */
55: public interface Consumer {
56: /**
57: * Initialize - allocate any resources required to operate. This may include
58: * initializing any pooled JMS resources. Called ONCE when created by the
59: * dispatcher pool. This should be used to set up expensive resources that
60: * will remain for the lifetime of the consumer.
61: */
62: public void initialize() throws Exception;
63:
64: /**
65: * Consume an event; events may get filtered at the dispatcher level, hiding
66: * it from the consumer. This behavior is based on the dispatcher/consumer
67: * configuration. Should include logic to initialize any resources required
68: * for a batch of events.
69: *
70: * @param ctx
71: * the execution context object
72: *
73: * @param event
74: * the content event
75: */
76: public void consume(Context ctx, Event event) throws Exception;
77:
78: /**
79: * Signal that there are no more events queued in this event stream and
80: * event processing for the preceding consume calls should be finished up.
81: */
82: public void end(Context ctx) throws Exception;
83:
84: /**
85: * Finish - free any allocated resources. Called when consumer (via it's
86: * parent dispatcher) is going to be destroyed by the dispatcher pool.
87: */
88: public void finish(Context ctx) throws Exception;
89:
90: }
|