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


1 /* ====================================================================
2  * The Jcorporate Apache Style Software License, Version 1.2 05-07-2002
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59  * <http://www.jcorporate.com/>.
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61  * Portions of this software are based upon other open source
62  * products and are subject to their respective licenses.
63  */
64
65 package com.jcorporate.expresso.kernel;
66
67 import com.jcorporate.expresso.kernel.metadata.ComponentMetadata;
68
69 import java.util.Iterator JavaDoc;
70
71 /**
72  * An <code>Embedded Component</code> is a component that is (1) Not a container
73  * and (2) it's metadata is embedded within the metadata of its parent. This
74  * allows for the guarantee that if one component is installed that it can bring
75  * its required components with it. An example is PersistenceManager
76  *
77  * @author Michael Rimov
78  * @see com.jcorporate.expresso.core.dataobjects.PersistenceManager
79  */
80
81 abstract public class EmbeddedComponent implements ExpressoComponent {
82
83     /**
84      * Cached metadata once we've looked it up from the parent
85      */
86     private ComponentMetadata myMetadata = null;
87
88     /**
89      * Parent Container Reference
90      */
91
92     private Containable myParent = null;
93
94
95     /**
96      * Default Do Nothing Constructor
97      */
98     public EmbeddedComponent() {
99     }
100
101     /**
102      * Because we look up our metadata in the parent component, we have to
103      * somehow know WHAT component's metadata is ours. Sub classes need to
104      * override this one-liner and return the name of the metadata we're
105      * looking for.
106      *
107      * @return java.lang.String
108      */
109     abstract public String JavaDoc getMetadataName();
110
111     /**
112      * Returns the metadata by retrieving the appropriate metadata from the parent
113      *
114      * @return ComponentMetadata for this component.
115      * @throws IllegalArgumentException if the parent cannot be queried for the
116      * appropriate metadata
117      */
118     public synchronized ComponentMetadata getMetaData() {
119         if (myMetadata == null) {
120             ExpressoComponent ec = (ExpressoComponent) this.getParent();
121             ComponentMetadata parentMetadata = ec.getMetaData();
122
123             for (Iterator JavaDoc i = parentMetadata.getChildren().iterator(); i.hasNext();) {
124                 ComponentMetadata oneChild = (ComponentMetadata) i.next();
125                 if (this.getMetadataName().equals(oneChild.getName())) {
126                     myMetadata = oneChild;
127                     break;
128                 }
129             }
130
131             if (myMetadata == null) {
132                 throw new IllegalArgumentException JavaDoc("Unable to find metadata " +
133                         "in parent corresponding to component named: "
134                         + this.getMetadataName());
135             }
136         }
137
138         return myMetadata;
139     }
140
141
142     /**
143      * Retrieve the parent component [if any]. May return null.
144      *
145      * @return ExpressoComponent or null
146      */
147     public synchronized Containable getParent() {
148         return myParent;
149     }
150
151     /**
152      * Called by the parent upon initial Expresso component creation so that the
153      * child component can find it's container.
154      *
155      * @param parent the 'containing' component.
156      */
157     public synchronized void setParent(Containable parent) {
158         myParent = parent;
159     }
160
161
162 }
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