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Java > Open Source Codes > org > apache > turbine > pipeline > BranchPointValve


1 package org.apache.turbine.pipeline;
2
3 /* ====================================================================
4  * The Apache Software License, Version 1.1
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9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
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14  * notice, this list of conditions and the following disclaimer.
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16  * 2. Redistributions in binary form must reproduce the above copyright
17  * notice, this list of conditions and the following disclaimer in
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19  * distribution.
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21  * 3. The end-user documentation included with the redistribution,
22  * if any, must include the following acknowledgment:
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25  * Alternately, this acknowledgment may appear in the software itself,
26  * if and wherever such third-party acknowledgments normally appear.
27  *
28  * 4. The names "Apache" and "Apache Software Foundation" and
29  * "Apache Turbine" must not be used to endorse or promote products
30  * derived from this software without prior written permission. For
31  * written permission, please contact apache@apache.org.
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33  * 5. Products derived from this software may not be called "Apache",
34  * "Apache Turbine", nor may "Apache" appear in their name, without
35  * prior written permission of the Apache Software Foundation.
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45  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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51  * This software consists of voluntary contributions made by many
52  * individuals on behalf of the Apache Software Foundation. For more
53  * information on the Apache Software Foundation, please see
54  * <http://www.apache.org/>.
55  */
56
57 import java.io.IOException JavaDoc;
58
59 import org.apache.turbine.Pipeline;
60 import org.apache.turbine.RunData;
61 import org.apache.turbine.TurbineException;
62 import org.apache.turbine.ValveContext;
63
64 /**
65  * A {@link org.apache.turbine.Valve} description of a pipeline's
66  * branch point. It may itself be the start of zero or more {@link
67  * org.apache.turbine.Pipeline} paths, and can even continue executing
68  * the pipeline that the branch point resides on after its branch
69  * pipelines finish.
70  *
71  * @author <a HREF="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
72  * @version $Id: BranchPointValve.java,v 1.7 2003/11/23 00:42:22 mpoeschl Exp $
73  */
74 public abstract class BranchPointValve
75     extends AbstractValve
76 {
77     /**
78      * A constant indicating no sub-pipelines.
79      */
80     protected static final Pipeline[] NO_PIPELINES = new Pipeline[0];
81
82     /**
83      * Sub-pipelines which we may branch process off into.
84      */
85     protected Pipeline[] pipelines = NO_PIPELINES;
86
87     /**
88      * Initializes all sub-pipelines.
89      *
90      * @see org.apache.turbine.Valve#initialize
91      */
92     public void initialize()
93         throws Exception JavaDoc
94     {
95         if (pipelines != NO_PIPELINES)
96         {
97             for (int i = 0; i < pipelines.length; i++)
98             {
99                 pipelines[i].initialize();
100             }
101         }
102     }
103
104     /**
105      * <p>Selects which pipeline path to branch down. This may just
106      * consist of calling <code>context.invokeNext(data)</code> to
107      * continue down the current pipeline's path. The desired branch
108      * path is generally determined using data pulled from the
109      * supplied<code>RunData</code>.</p>
110      *
111      * <p>Here's an illustration of inserting a
112      * <code>BranchPointValve</code> into the
113      * <code>TurbinePipeline</code> processing sequence:
114      *
115      * <blockquote><pre>
116      * ___ (start of FooPipeline)
117      * /
118      * ---[Valve]--[Valve]--[BranchPointValve]---- (continue w/ TurbinePipeline)
119      * \
120      * --- (start of BarPipeline)
121      * </pre></blockquote>
122      *
123      * The <code>BranchPointValve</code> could just as easily stop all
124      * processing by neither invoking a new pipeline nor calling
125      * <code>invokeNext()</code>.
126      * </p>
127      *
128      * @param data The run-time data.
129      * @exception IOException Problem choosing pipeline to branch down.
130      * @exception TurbineException Problem choosing pipeline to branch down.
131      * @see org.apache.turbine.Valve#invoke(RunData, ValveContext)
132      */
133     public abstract void invoke(RunData data, ValveContext context)
134         throws IOException JavaDoc, TurbineException;
135 }
136
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