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


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55 package org.apache.avalon.framework.component;
56
57 import java.util.HashMap JavaDoc;
58 import java.util.Map JavaDoc;
59
60 /**
61  * This is the default implementation of the ComponentSelector.
62  *
63  * <p>
64  * <span style="color: red">Deprecated: </span><i>
65  * Use {@link org.apache.avalon.framework.service.DefaultServiceSelector} instead.
66  * </i>
67  * </p>
68  *
69  * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
70  * @version CVS $Revision: 1.21 $ $Date: 2003/02/11 15:58:38 $
71  */

72 public class DefaultComponentSelector
73     implements ComponentSelector
74 {
75     private final HashMap JavaDoc m_components = new HashMap JavaDoc();
76     private boolean m_readOnly;
77
78     /**
79      * Select the desired component. It does not cascade, neither
80      * should it.
81      *
82      * @param hint the hint to retrieve Component
83      * @return the Component
84      * @throws ComponentException if an error occurs
85      */

86     public Component select( Object JavaDoc hint )
87         throws ComponentException
88     {
89         final Component component = (Component)m_components.get( hint );
90
91         if( null != component )
92         {
93             return component;
94         }
95         else
96         {
97             throw new ComponentException( hint.toString(), "Unable to provide implementation." );
98         }
99     }
100
101     /**
102      * Returns whether a Component exists or not
103      * @param hint the hint to retrieve Component
104      * @return <code>true</code> if the Component exists
105      */

106     public boolean hasComponent( final Object JavaDoc hint )
107     {
108         boolean componentExists = false;
109
110         try
111         {
112             this.release( this.select( hint ) );
113             componentExists = true;
114         }
115         catch( Throwable JavaDoc t )
116         {
117             // Ignore all throwables--we want a yes or no answer.
118
}
119
120         return componentExists;
121     }
122
123     /**
124      * Release component.
125      *
126      * @param component the component
127      */

128     public void release( final Component component )
129     {
130         // if the ComponentManager handled pooling, it would be
131
// returned to the pool here.
132
}
133
134     /**
135      * Populate the ComponentSelector.
136      * @param hint the hint to retrieve Component
137      * @param component the component to add
138      */

139     public void put( final Object JavaDoc hint, final Component component )
140     {
141         checkWriteable();
142         m_components.put( hint, component );
143     }
144
145     /**
146      * Helper method for subclasses to retrieve component map.
147      *
148      * @return the component map
149      */

150     protected final Map JavaDoc getComponentMap()
151     {
152         return m_components;
153     }
154
155     /**
156      * Make this component selector read-only.
157      */

158     public void makeReadOnly()
159     {
160         m_readOnly = true;
161     }
162
163     /**
164      * Check if this component m_manager is writeable.
165      *
166      * @throws IllegalStateException if this component m_manager is read-only
167      */

168     protected final void checkWriteable()
169         throws IllegalStateException JavaDoc
170     {
171         if( m_readOnly )
172         {
173             throw new IllegalStateException JavaDoc
174                 ( "ComponentSelector is read only and can not be modified" );
175         }
176     }
177 }
178
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