Ignoring ClassLoader Roots

[alrubinger]

In doing some prototyping on AS Embedded, I've run into an issue where the bootstrap deployables in AS fail on definition of explicit roots:

<classloader name="aop-classloader" xmlns="urn:jboss:classloader:1.0" export-all="NON_EMPTY" import-all="true">
 <root>${jboss.lib.url}jboss-aop-asintegration-core.jar</root>
...etc
 </classloader>

Ales kindly provided me with a NoopClassLoaderFactory:

http://anonsvn.jboss.org/repos/jbossas/projects/jboss-cl/trunk/classloading-vfs/src/test/java/org/jboss/test/classloading/vfs/metadata/xml/support/NoopClassLoaderFactory.java

...which has overridden:

@XmlTransient
 public List<BeanMetaData> getBeans()
 {
 return Collections.emptyList();
 }

Though what's needed is an implementation that won't allow "roots" to be specified, so I've rewritten this in a (as of yet uncommitted) implementation in the new jboss-embedded-core project. This will be in SVN once I've got the proper JIRA rights to organize up and keep things documented.

Perhaps MC wants this code instead?

/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2008, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.embedded.classloading;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.xml.bind.annotation.XmlNsForm;
import javax.xml.bind.annotation.XmlRootElement;

import org.jboss.classloading.spi.vfs.metadata.VFSClassLoaderFactory;
import org.jboss.xb.annotations.JBossXmlSchema;

/**
 * NoOpClassLoaderFactory
 *
 * ClassLoader Factory that will not allow roots to be added
 *
 * @author <a href="mailto:[e-mail]">ALR</a>
 * @version $Revision: $
 */
@JBossXmlSchema(namespace = "urn:jboss:classloader:1.0", elementFormDefault = XmlNsForm.QUALIFIED)
@XmlRootElement(name = "classloader")
public class NoOpClassLoaderFactory extends VFSClassLoaderFactory
{
 //------------------------------------------------------------------||
 // Class Members ---------------------------------------------------||
 //------------------------------------------------------------------||

 private static final long serialVersionUID = 1L;

 //------------------------------------------------------------------||
 // Instance Members ------------------------------------------------||
 //------------------------------------------------------------------||

 /**
 * Empty list which may never have contents. Synchronization policy
 * on "this".
 */
 private volatile List<String> emptyList;

 //------------------------------------------------------------------||
 // Accessors / Mutators --------------------------------------------||
 //------------------------------------------------------------------||

 /**
 * An overridden implementation to obtain the roots for
 * this CL, which will always contain no elements
 */
 @Override
 public List<String> getRoots()
 {
 return this.getEmptyList();
 }

 //------------------------------------------------------------------||
 // Internal Helper Methods -----------------------------------------||
 //------------------------------------------------------------------||

 /**
 * Obtains an empty list (which may never become
 * filled with any elements)
 *
 * @return
 */
 private List<String> getEmptyList()
 {
 // Initialize
 List<String> returnValue = this.emptyList;

 // Check that underlying list is instanciated
 if (returnValue == null)
 {
 // Sync up
 synchronized (this)
 {
 // Double-check for instanciation
 if (returnValue == null)
 {
 // Create the underlying list
 this.emptyList = returnValue = new NoOpAdditiveList<String>();
 }
 }
 }

 // Return
 return returnValue;
 }

 //------------------------------------------------------------------||
 // Inner Classes ---------------------------------------------------||
 //------------------------------------------------------------------||

 /**
 * NoOpAdditiveOperationsList
 *
 * An extension of ArrayList where the general contract
 * of "Collection.add" is violated in favor of a NOOP
 * implementation
 *
 * May be used in place of immutable lists when additions
 * should silently not take place, instead of throwing
 * UnsupportedOperationException
 *
 * @author <a href="mailto:[e-mail]">ALR</a>
 * @version $Revision: $
 * @param <E>
 */
 private static class NoOpAdditiveOperationsList<E> extends ArrayList<E>
 {

 private static final long serialVersionUID = 1L;

 @Override
 public boolean add(E o)
 {
 return true;
 }

 @Override
 public void add(int index, E element)
 {
 return;
 }

 @Override
 public boolean addAll(Collection<? extends E> c)
 {
 return true;
 }

 @Override
 public boolean addAll(int index, Collection<? extends E> c)
 {
 return true;
 }

 }

}

S,
ALR

[alesj]

"ALRubinger" wrote:

Perhaps MC wants this code instead?

No. :-)
We're fine with our example.

The point of my example was to check
how easy it is to change classloading metadata.
What kind of behavior you put in it's entirely up to you.
e.g. in your case you also had to ignore roots