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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.
The newest version!
/*
* 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.jdk;
import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
/*
* JDK 1.1 Style Hooks implementation.
*/
public class JDK11Hooks extends JDKHooks {
private static final ClassLoader systemClassLoader = new PsuedoSystemClassLoader();
/*
* {@inheritDoc}
*/
@Override
public String getSystemProperty(final String propName) {
return System.getProperty(propName);
}
/*
* {@inheritDoc}
*/
@Override
public ClassLoader getThreadContextClassLoader() {
return null;
}
/*
* {@inheritDoc}
*/
@Override
public ClassLoader getSystemClassLoader() {
return systemClassLoader;
}
/*
* {@inheritDoc}
*/
@Override
public Enumeration getResources(ClassLoader loader, String resourceName) throws IOException {
/*
* The simple answer is/was:
* return loader.getResources(resourceName);
*
* However, some classloaders overload the behavior of getResource
* (loadClass, etc) such that the order of returned results changes
* from normally expected behavior.
*
* Example: locate classes/resources from child ClassLoaders first,
* parents last (in some J2EE environs).
*
* The resource returned by getResource() should be the same as the
* first resource returned by getResources(). Unfortunately, this
* is not, and cannot be: getResources() is 'final' in the current
* JDK's (1.2, 1.3, 1.4).
*
* To address this, the implementation of this method will
* return an Enumeration such that the first element is the
* results of getResource, and all trailing elements are
* from getResources. On each iteration, we check so see
* if the resource (from getResources) matches the first resource,
* and eliminate the redundent element.
*/
final URL first = loader.getResource(resourceName);
final Enumeration rest = loader.getResources(resourceName);
return new Enumeration() {
private boolean firstDone = (first == null);
private URL next = getNext();
public URL nextElement() {
URL o = next;
next = getNext();
return o;
}
public boolean hasMoreElements() {
return next != null;
}
private URL getNext() {
URL n;
if (!firstDone) {
/*
* First time through, use results of getReference()
* if they were non-null.
*/
firstDone = true;
n = first;
} else {
/*
* Subsequent times through,
* use results of getReferences()
* but take out anything that matches 'first'.
*
* Iterate through list until we find one that
* doesn't match 'first'.
*/
n = null;
while (rest.hasMoreElements() && n == null) {
n = rest.nextElement();
if (first != null &&
n != null &&
n.equals(first))
{
n = null;
}
}
}
return n;
}
};
}
}