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1 /*
2  * The Apache Software License, Version 1.1
3  *
4  * Copyright (c) 2002 The Apache Software Foundation. All rights
5  * reserved.
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7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  *
11  * 1. Redistributions of source code must retain the above copyright
12  * notice, this list of conditions and the following disclaimer.
13  *
14  * 2. Redistributions in binary form must reproduce the above copyright
15  * notice, this list of conditions and the following disclaimer in
16  * the documentation and/or other materials provided with the
17  * distribution.
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19  * 3. The end-user documentation included with the redistribution, if
20  * any, must include the following acknowlegement:
21  * "This product includes software developed by the
22  * Apache Software Foundation (http://www.apache.org/)."
23  * Alternately, this acknowlegement may appear in the software itself,
24  * if and wherever such third-party acknowlegements normally appear.
25  *
26  * 4. The names "Apache BSF", "Apache", and "Apache Software Foundation"
27  * must not be used to endorse or promote products derived from
28  * this software without prior written permission. For written
29  * permission, please contact apache@apache.org.
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31  * 5. Products derived from this software may not be called "Apache"
32  * nor may "Apache" appear in their names without prior written
33  * permission of the Apache Group.
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35  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
36  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
37  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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39  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
41  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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43  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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47  * ====================================================================
48  *
49  * This software consists of voluntary contributions made by many individuals
50  * on behalf of the Apache Software Foundation and was originally created by
51  * Sanjiva Weerawarana and others at International Business Machines
52  * Corporation. For more information on the Apache Software Foundation,
53  * please see <http://www.apache.org/>.
54  */
55
56 package org.apache.bsf.util;
57
58 import java.util.*;
59
60 /**
61  * The <em>ObjectRegistry</em> is used to do name-to-object reference lookups.
62  * If an <em>ObjectRegistry</em> is passed as a constructor argument, then this
63  * <em>ObjectRegistry</em> will be a cascading registry: when a lookup is
64  * invoked, it will first look in its own table for a name, and if it's not
65  * there, it will cascade to the parent <em>ObjectRegistry</em>.
66  * All registration is always local. [??]
67  *
68  * @author Sanjiva Weerawarana
69  * @author Matthew J. Duftler
70  */
71 public class ObjectRegistry {
72   Hashtable reg = new Hashtable ();
73   ObjectRegistry parent = null;
74
75   public ObjectRegistry () {
76   }
77   public ObjectRegistry (ObjectRegistry parent) {
78     this.parent = parent;
79   }
80   // lookup an object: cascade up if needed
81 public Object JavaDoc lookup (String JavaDoc name) throws IllegalArgumentException JavaDoc {
82     Object JavaDoc obj = reg.get (name);
83
84     if (obj == null && parent != null) {
85       obj = parent.lookup (name);
86     }
87
88     if (obj == null) {
89       throw new IllegalArgumentException JavaDoc ("object '" + name + "' not in registry");
90     }
91
92     return obj;
93   }
94   // register an object
95 public void register (String JavaDoc name, Object JavaDoc obj) {
96     reg.put (name, obj);
97   }
98   // unregister an object (silent if unknown name)
99 public void unregister (String JavaDoc name) {
100     reg.remove (name);
101   }
102 }
103
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