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Java > Open Source Codes > com > jcorporate > expresso > kernel > ContainerComponentBase


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64 package com.jcorporate.expresso.kernel;
65
66 import EDU.oswego.cs.dl.util.concurrent.ReadWriteLock;
67 import EDU.oswego.cs.dl.util.concurrent.WriterPreferenceReadWriteLock;
68 import org.apache.log4j.Logger;
69
70 /**
71  * This class provides basic implementations of the Containable Interface to
72  * save the typical programmer lots of typing. Under 99% of the conditions it
73  * should be sufficient to derivce your container component from this class
74  * instead of implementing the interfaces in a raw fashion.
75  *
76  * @author Michael Rimov
77  * @since Expresso 5.1
78  */
79 abstract public class ContainerComponentBase extends ComponentBase implements Containable {
80
81     /**
82      * Read Write lock on the container
83      */
84     private ReadWriteLock containerLock = new WriterPreferenceReadWriteLock();
85
86
87     /**
88      * The log4j Logger
89      */
90     private static Logger log = Logger.getLogger(ContainerComponentBase.class);
91
92     /**
93      * This is the 1:1 implementation class. (One exists for each containable component)
94      */
95     private ComponentContainer implementation;
96
97     /**
98      * Default constructor that currently does nothing.
99      */
100     public ContainerComponentBase() {
101         super();
102     }
103
104
105     /**
106      * Sets the marker to the ComponentContainer (which has a 1:1 instance mapping
107      * with Containable). This is often called by the actual implementation
108      * of the ComponentContainer.
109      *
110      * @param newContainer a <code>ComponentCo
111      */
112     public synchronized void setContainerImplementation(ComponentContainer newContainer) {
113         try {
114             containerLock.writeLock().acquire();
115         } catch (InterruptedException JavaDoc ex) {
116             log.error("Interrupted while waiting for write lock. Aborting method", ex);
117         }
118         implementation = newContainer;
119
120         containerLock.writeLock().release();
121     }
122
123
124     /**
125      * Retrieves the actual container implementation
126      *
127      * @return ComponentContainer
128      */
129     public synchronized ComponentContainer getContainerImplementation() {
130         try {
131             containerLock.readLock().acquire();
132         } catch (InterruptedException JavaDoc ex) {
133             log.error("Interrupted while waiting for read lock. Aborting method", ex);
134         }
135
136         try {
137             return implementation;
138         } finally {
139             containerLock.readLock().release();
140         }
141     }
142
143     /**
144      * <p>Convenience method for Container clients. Recommended
145      * Implementation:</p>
146      * <p/>
147      * <code>
148      * ExpressoComponent getComponent(String componentName) {<br />
149      * &nbsp;&nbsp; return this.getContainerImplementation().getComponent(componentName);
150      * }<br />
151      * <p/>
152      * </code>
153      * </p>
154      *
155      * @param componentName The name of the component to retrieve
156      * @return an ExpressoComponent or null if the specified name doesn't exist
157      */
158     public synchronized ExpressoComponent locateComponent(String JavaDoc componentName) {
159         try {
160             containerLock.readLock().acquire();
161         } catch (InterruptedException JavaDoc ex) {
162             log.error("Interrupted while waiting for read lock. Aborting method", ex);
163         }
164
165         try {
166             return implementation.locateComponent(componentName);
167         } finally {
168             containerLock.readLock().release();
169         }
170     }
171 }
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