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Java > Open Source Codes > org > apache > avalon > framework > component > ComponentSelector


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55 package org.apache.avalon.framework.component;
56
57 /**
58  * A <code>ComponentSelector</code> selects <code>Component</code>s based on a
59  * hint. The contract is that all the <code>Component</code>s implement the
60  * same role.
61  *
62  * <p>
63  * A role is better understood by the analogy of a play. There are many
64  * different roles in a script. Any actor or actress can play any given part
65  * and you get the same results (phrases said, movements made, etc.). The exact
66  * nuances of the performance is different.
67  * </p>
68  *
69  * <p>
70  * Below is a list of things that might be considered the same role:
71  * </p>
72  *
73  * <ul>
74  * <li> XMLInputAdapter and PropertyInputAdapter</li>
75  * <li> FileGenerator and SQLGenerator</li>
76  * </ul>
77  *
78  * <p>
79  * The <code>ComponentSelector</code> does not specify the methodology of
80  * getting the <code>Component</code>, merely the interface used to get it.
81  * Therefore the <code>ComponentSelector</code> can be implemented with a
82  * factory pattern, an object pool, or a simple Hashtable.
83  * </p>
84  *
85  * <p>
86  * <span style="color: red">Deprecated: </span><i>
87  * Use {@link org.apache.avalon.framework.service.ServiceSelector} instead.
88  * </i>
89  * </p>
90  *
91  * @see org.apache.avalon.framework.component.Component
92  * @see org.apache.avalon.framework.component.Composable
93  * @see org.apache.avalon.framework.component.ComponentManager
94  *
95  * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
96  * @version CVS $Revision: 1.19 $ $Date: 2003/02/11 15:58:38 $
97  */
98 public interface ComponentSelector
99     extends Component
100 {
101     /**
102      * Select the <code>Component</code> associated with the given hint.
103      * For instance, If the <code>ComponentSelector</code> has a
104      * <code>Generator</code> stored and referenced by a URL, I would use the
105      * following call:
106      *
107      * <pre>
108      * try
109      * {
110      * Generator input;
111      * input = (Generator)selector.select( new URL("foo://demo/url") );
112      * }
113      * catch (...)
114      * {
115      * ...
116      * }
117      * </pre>
118      *
119      * @param hint A hint to retrieve the correct <code>Component</code>.
120      * @return the desired component
121      * @throws ComponentException If the given role is not associated
122      * with a <code>Component</code>, or a
123      * <code>Component</code> instance cannot
124      * be created.
125      */
126     Component select( Object JavaDoc hint )
127         throws ComponentException;
128
129     /**
130      * Check to see if a <code>Component</code> exists for a hint.
131      *
132      * @param hint a string identifying the role to check.
133      * @return True if the component exists, False if it does not.
134      */
135     boolean hasComponent( Object JavaDoc hint );
136
137     /**
138      * Return the <code>Component</code> when you are finished with it. This
139      * allows the <code>ComponentSelector</code> to handle the End-Of-Life Lifecycle
140      * events associated with the Component. Please note, that no Exceptions
141      * should be thrown at this point. This is to allow easy use of the
142      * ComponentSelector system without having to trap Exceptions on a release.
143      *
144      * @param component The Component we are releasing.
145      */
146     void release( Component component );
147 }
148
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