org.aspectj/weaver/src/main/java/org/aspectj/weaver/bcel/BcelWeakClassLoaderReference.java

/* *******************************************************************
 * Copyright (c) 2008 Contributors
 * All rights reserved.
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Public License v 2.0
 * which accompanies this distribution and is available at
 * https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.txt
 *
 * Contributors:
 *     Andy Clement     initial implementation
 * ******************************************************************/
package org.aspectj.weaver.bcel;

import org.aspectj.apache.bcel.util.ClassLoaderReference;
import org.aspectj.weaver.WeakClassLoaderReference;

/**
 * Wraps a reference to a classloader inside a WeakReference. This should be used where we do not want the existence of a
 * classloader reference to prevent garbage collection of that classloader (and possibly an associated weaver instance in the case
 * of load time weaving).
 * <p>
 * In more detail:<br>
 * When load time weaving, the class Aj maintains a WeakHashMap from the classloader instance to a weaver instance. The aim is that
 * the weaver is around as long as the classloader is and should the classloader be dereferenced then the weaver can also be garbage
 * collected. The problem is that if there are many references to the classloader from within the weaver, these are considered hard
 * references and cause the classloader to be long lived - even if the user of the classloader has dereferenced it in their code.
 * The solution is that the weaver should use instances of WeakClassLoaderReference objects - so that when the users hard reference
 * to the classloader goes, nothing in the weaver will cause it to hang around. There is a big assertion here that the
 * WeakClassLoaderReference instances will not 'lose' their ClassLoader references until the top level ClassLoader reference is
 * null'd. This means there is no need to check for the null case on get() in this WeakReference logic below, because we shouldn't
 * be using this weaver if its associated ClassLoader has been collected. See https://bugs.eclipse.org/bugs/show_bug.cgi?id=210470
 *
 *
 * @author Andy Clement
 */
public class BcelWeakClassLoaderReference extends WeakClassLoaderReference implements ClassLoaderReference {

	public BcelWeakClassLoaderReference(ClassLoader loader) {
		super(loader);
	}

	public boolean equals(Object obj) {
		if (!(obj instanceof BcelWeakClassLoaderReference))
			return false;
		BcelWeakClassLoaderReference other = (BcelWeakClassLoaderReference) obj;
		return (other.hashcode == hashcode);
	}

}