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Its an port to fix bugs in OSGi support. ... The Apache Commons Discovery 0.5 component is about discovering, or finding,
implementations for pluggable interfaces.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.discovery;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* 'Resource' located by discovery.
* Naming of methods becomes a real pain ('getClass()')
* so I've patterned this after ClassLoader...
*
* I think it works well as it will give users a point-of-reference.
*
* @param The SPI type
*/
public class ResourceClass extends Resource {
private static Log log = LogFactory.getLog(ResourceClass.class);
/**
* Sets the {@code Log} for this class.
*
* @param _log This class {@code Log}
* @deprecated This method is not thread-safe
*/
@Deprecated
public static void setLog(Log _log) {
log = _log;
}
protected Class resourceClass;
/**
* Create a new {@code Resource} class located by discovery.
*
* @param Any type extends T
* @param resourceClass The resource class has to be located
* @param resource The resource URL has to be located
*/
public ResourceClass(Class resourceClass, URL resource) {
super(resourceClass.getName(), resource, resourceClass.getClassLoader());
this.resourceClass = resourceClass;
}
/**
* Create a new {@code Resource} class located by discovery.
*
* @param resourceName The resource class name has to be located
* @param resource The resource URL has to be located
* @param loader The class loaders holder
*/
public ResourceClass(String resourceName, URL resource, ClassLoader loader) {
super(resourceName, resource, loader);
}
/**
* Get the value of resourceClass.
* Loading the class does NOT guarentee that the class can be
* instantiated. Go figure.
* The class can be instantiated when the class is linked/resolved,
* and all dependencies are resolved.
* Various JDKs do this at different times, so beware:
* java.lang.NoClassDefFoundError when
* calling Class.getDeclaredMethod() (JDK14),
* java.lang.reflect.InvocationTargetException
* (wrapping java.lang.NoClassDefFoundError) when calling
* java.lang.newInstance (JDK13),
* and who knows what else..
*
* @param Any type extends T
*
* @return value of resourceClass.
*/
public Class loadClass() {
if (resourceClass == null && getClassLoader() != null) {
if (log.isDebugEnabled()) {
log.debug("loadClass: Loading class '" + getName() + "' with " + getClassLoader());
}
resourceClass = AccessController.doPrivileged(
new PrivilegedAction>() {
public Class run() {
try {
@SuppressWarnings("unchecked") // this can raise a ClassCastException at runtime
Class returned = (Class) getClassLoader().loadClass(getName());
return returned;
} catch (ClassNotFoundException e) {
return null;
}
}
});
}
@SuppressWarnings("unchecked") // this is assumed by default, see the ctor
Class returned = (Class) resourceClass;
return returned;
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
return "ResourceClass[" + getName() + ", " + getResource() + ", " + getClassLoader() + "]";
}
}