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


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55 package org.apache.avalon.framework.component;
56
57 import org.apache.avalon.framework.service.ServiceManager;
58 import org.apache.avalon.framework.service.ServiceException;
59 import org.apache.avalon.framework.service.ServiceSelector;
60
61 /**
62  * This is a {@link ComponentManager} implementation that can wrap around a
63  * {@link ServiceManager} object effectively adapting a {@link ServiceManager}
64  * interface to a {@link ComponentManager} interface.
65  *
66  * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
67  * @version CVS $Revision: 1.14 $ $Date: 2003/02/14 15:13:12 $
68  */
69 public class WrapperComponentManager
70     implements ComponentManager
71 {
72     /**
73      * The service manager we are adapting.
74      */
75     private final ServiceManager m_manager;
76
77    /**
78     * Creation of a new wrapper component manger using a supplied
79     * service manager as a source backing the wrapped. This implementation
80     * redirects lookup requests to the supplied service manager provided under
81     * this constructor. No attempt is made to proxy object supplied by the
82     * primary manager as Component instances - as such, it is the responsibility
83     * of the application establishing the wrapper to ensure that objects
84     * accessed via the primary manager implement the Component interface.
85     *
86     * @param manager the service manager backing the wrapper.
87     */
88     public WrapperComponentManager( final ServiceManager manager )
89     {
90         if( null == manager )
91         {
92             throw new NullPointerException JavaDoc( "manager" );
93         }
94
95         m_manager = manager;
96     }
97
98     /**
99      * Retrieve a component via a key.
100      *
101      * @param key the key
102      * @return the component
103      * @throws ComponentException if unable to aquire component
104      */
105     public Component lookup( final String JavaDoc key )
106         throws ComponentException
107     {
108         try
109         {
110             final Object JavaDoc object = m_manager.lookup( key );
111             if( object instanceof ServiceSelector )
112             {
113                 return new WrapperComponentSelector( key, (ServiceSelector)object );
114             }
115             else if( object instanceof Component )
116             {
117                 return (Component)object;
118             }
119         }
120         catch( final ServiceException se )
121         {
122             throw new ComponentException( se.getKey(), se.getMessage(), se.getCause() );
123         }
124
125         final String JavaDoc message = "Role does not implement the Component "
126             + "interface and thus can not be accessed via ComponentManager";
127         throw new ComponentException( key, message );
128     }
129
130     /**
131      * Check to see if a <code>Component</code> exists for a key.
132      *
133      * @param key a string identifying the key to check.
134      * @return True if the component exists, False if it does not.
135      */
136     public boolean hasComponent( final String JavaDoc key )
137     {
138         return m_manager.hasService( key );
139     }
140
141     /**
142      * Return the <code>Component</code> when you are finished with it. This
143      * allows the <code>ComponentManager</code> to handle the End-Of-Life Lifecycle
144      * events associated with the Component. Please note, that no Exceptions
145      * should be thrown at this point. This is to allow easy use of the
146      * ComponentManager system without having to trap Exceptions on a release.
147      *
148      * @param component The Component we are releasing.
149      */
150     public void release( final Component component )
151     {
152         if( component instanceof WrapperComponentSelector )
153         {
154             m_manager.
155                 release( ( (WrapperComponentSelector)component ).getWrappedSelector() );
156         }
157         else
158         {
159             m_manager.release( component );
160         }
161     }
162 }
163
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