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Java > Open Source Codes > org > mr > core > util > AbstractStage


1 /*
2  * Copyright 2002 by
3  * <a HREF="http://www.coridan.com">Coridan</a>
4  * <a HREF="mailto: support@coridan.com ">support@coridan.com</a>
5  *
6  * The contents of this file are subject to the Mozilla Public License Version
7  * 1.1 (the "License"); you may not use this file except in compliance with the
8  * License. You may obtain a copy of the License at
9  * http://www.mozilla.org/MPL/
10  *
11  * Software distributed under the License is distributed on an "AS IS" basis,
12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13  * for the specific language governing rights and limitations under the
14  * License.
15  *
16  * The Original Code is "MantaRay" (TM).
17  *
18  * The Initial Developer of the Original Code is Amir Shevat.
19  * Portions created by the Initial Developer are Copyright (C) 2006
20  * Coridan Inc. All Rights Reserved.
21  *
22  * Contributor(s): all the names of the contributors are added in the source
23  * code where applicable.
24  *
25  * Alternatively, the contents of this file may be used under the terms of the
26  * LGPL license (the "GNU LESSER GENERAL PUBLIC LICENSE"), in which case the
27  * provisions of LGPL are applicable instead of those above. If you wish to
28  * allow use of your version of this file only under the terms of the LGPL
29  * License and not to allow others to use your version of this file under
30  * the MPL, indicate your decision by deleting the provisions above and
31  * replace them with the notice and other provisions required by the LGPL.
32  * If you do not delete the provisions above, a recipient may use your version
33  * of this file under either the MPL or the GNU LESSER GENERAL PUBLIC LICENSE.
34  
35  *
36  * This library is free software; you can redistribute it and/or modify it
37  * under the terms of the MPL as stated above or under the terms of the GNU
38  * Lesser General Public License as published by the Free Software Foundation;
39  * either version 2.1 of the License, or any later version.
40  *
41  * This library is distributed in the hope that it will be useful, but WITHOUT
42  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
43  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
44  * License for more details.
45  */

46 /*
47  * Created on Dec 31, 2003
48  * Manta LTD
49  */

50 package org.mr.core.util;
51
52 import java.util.ArrayList JavaDoc;
53
54 import org.apache.commons.logging.LogFactory;
55 import org.apache.commons.logging.Log;
56
57 /**
58  * AbstractStage represents a stage that holds a queue of events, following the stage
59  * design pattern.
60  * This queue encapsulate a logical layer (e.g. network, delivery, persistency ...).
61  * Each stage does its work and enqueues events to other stages when needed.
62  * The queue of events is active (has a dequeue threads), events are sent to the
63  * stage handler that preforms the logical task based on the event at hand.
64  *
65  * Created Dec 31, 2003
66  * Ver 1.0
67  * @author Amir Shevat
68  *
69  */

70  public abstract class AbstractStage {
71     StageParams params;
72     StageHandler handler;
73     ArrayList JavaDoc stageExecutionThreads = new ArrayList JavaDoc();
74     private Log log = null;
75     
76     /**
77      * Constructs a stage
78      * @param params The parameters of this stage.
79      */

80     public AbstractStage(StageParams params){
81         
82         this.params = params;
83         this.handler = params.getHandler();
84         log = LogFactory.getLog("AbstractStage");
85     }
86     
87     /**
88      * Dequeue from the queue of events.
89      * @return the object dequeded.
90      */

91     protected abstract Object JavaDoc dequeue();
92     
93     public final boolean sendToHandler(Object JavaDoc event){
94         try {
95             if(handler == null || event == null) {
96                 if(log.isErrorEnabled()) {
97                     log.error("Problem with stage: event="+event+" handler="+handler+" in"+
98                         "sendToHandler()in class AbstractStage.");
99                 }
100             }
101             else
102                 return handler.handle(event);
103         } catch(Throwable JavaDoc t) {
104             if(log.isErrorEnabled()) {
105                 log.error("Exception in stage "+params.getStageName(), t);
106             }
107         }
108         return true;
109     }
110 }
111
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