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package org.apache.commons.discovery.tools;
import org.apache.commons.discovery.ResourceClass;
import org.apache.commons.discovery.ResourceClassListener;
import org.apache.commons.discovery.resource.ClassLoaders;
import org.apache.commons.discovery.resource.classes.DiscoverClasses;
/**
* Holder for a default class.
*
* Class may be specified by name (String) or class (Class).
* Using the holder complicates the users job, but minimized # of API's.
*
* @author Richard A. Sitze
*/
public class DefaultClassHolder {
private Class defaultClass;
private final String defaultName;
public DefaultClassHolder(Class defaultClass) {
this.defaultClass = defaultClass;
this.defaultName = defaultClass.getName();
}
public DefaultClassHolder(String defaultName) {
this.defaultClass = null;
this.defaultName = defaultName;
}
/**
* @param spi non-null SPI
* @param loaders Used only if class needs to be loaded.
*
* @return Default Class. Load the class if necessary,
* and verify that it implements the SPI.
* (this forces the check, no way out..).
*/
public Class getDefaultClass(SPInterface spi, ClassLoaders loaders) {
if (defaultClass == null) {
ResourceClassListener listener =
new ResourceClassListener() {
public boolean found(ResourceClass resource) {
defaultClass = resource.loadClass();
return false; // only get first.
}
};
DiscoverClasses classDiscovery = new DiscoverClasses(loaders);
classDiscovery.setListener(listener);
classDiscovery.find(getDefaultName());
}
if (defaultClass != null) {
spi.verifyAncestory(defaultClass);
}
return defaultClass;
}
public String getDefaultName() {
return defaultName;
}
}