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Java > Open Source Codes > org > apache > commons > discovery > tools > DefaultClassHolder


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61
62 package org.apache.commons.discovery.tools;
63
64 import org.apache.commons.discovery.ResourceClass;
65 import org.apache.commons.discovery.ResourceClassListener;
66 import org.apache.commons.discovery.resource.ClassLoaders;
67 import org.apache.commons.discovery.resource.classes.DiscoverClasses;
68
69
70 /**
71  * Holder for a default class.
72  *
73  * Class may be specified by name (String) or class (Class).
74  * Using the holder complicates the users job, but minimized # of API's.
75  *
76  * @author Richard A. Sitze
77  */
78 public class DefaultClassHolder {
79     private Class JavaDoc defaultClass;
80     private final String JavaDoc defaultName;
81     
82     public DefaultClassHolder(Class JavaDoc defaultClass) {
83         this.defaultClass = defaultClass;
84         this.defaultName = defaultClass.getName();
85     }
86     
87     public DefaultClassHolder(String JavaDoc defaultName) {
88         this.defaultClass = null;
89         this.defaultName = defaultName;
90     }
91
92     /**
93      * @param spi non-null SPI
94      * @param loaders Used only if class needs to be loaded.
95      *
96      * @return Default Class. Load the class if necessary,
97      * and verify that it implements the SPI.
98      * (this forces the check, no way out..).
99      */
100     public Class JavaDoc getDefaultClass(SPInterface spi, ClassLoaders loaders) {
101         if (defaultClass == null) {
102             ResourceClassListener listener =
103                 new ResourceClassListener() {
104                     public boolean found(ResourceClass resource) {
105                         defaultClass = resource.loadClass();
106                         return false; // only get first.
107 }
108                 };
109             DiscoverClasses classDiscovery = new DiscoverClasses(loaders);
110             classDiscovery.setListener(listener);
111             classDiscovery.find(getDefaultName());
112         }
113         
114         if (defaultClass != null) {
115             spi.verifyAncestory(defaultClass);
116         }
117
118         return defaultClass;
119     }
120
121     public String JavaDoc getDefaultName() {
122         return defaultName;
123     }
124 }
125
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