/* * JBoss, Home of Professional Open Source * Copyright 2005, JBoss Inc., and individual contributors as indicated * by the @authors tag. See the copyright.txt 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.jbpm.instantiation; import java.lang.ref.SoftReference; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import org.jbpm.JbpmConfiguration; import org.jbpm.graph.def.ProcessDefinition; import org.jbpm.util.ClassLoaderUtil; /** * Factory that keeps soft references to the class loaders it produces, in order to prevent * duplicate class loaders from eating up the permanent generation space. The cache does not * prevent the garbage collector from discarding the class loaders. * * @author Alejandro Guizar */ public class SharedProcessClassLoaderFactory implements ProcessClassLoaderFactory { private JbpmConfiguration jbpmConfiguration; private transient Map classLoaderRefs = new HashMap(); private static final long serialVersionUID = 1L; public ClassLoader getProcessClassLoader(ProcessDefinition processDefinition) { // use database identifier as key to lookup cached class loader long id = processDefinition.getId(); // if process definition is transient, use hash code as key Long key = new Long(id == 0L ? processDefinition.hashCode() : id); // consider that the context class loader changes among applications ClassLoader parentClassLoader = ClassLoaderUtil.getClassLoader(); synchronized (classLoaderRefs) { // lookup cached class loader ClassLoader processClassLoader = getProcessClassLoader(key, parentClassLoader); // if class loader is not cached, if (processClassLoader == null) { // (re-)create class loader processClassLoader = new ProcessClassLoader(parentClassLoader, processDefinition, jbpmConfiguration); // add class loader to cache putProcessClassLoader(key, processClassLoader); } return processClassLoader; } } private ClassLoader getProcessClassLoader(Long processDefinitionKey, ClassLoader parentClassLoader) { List referenceList = (List) classLoaderRefs.get(processDefinitionKey); if (referenceList != null) { for (Iterator i = referenceList.iterator(); i.hasNext();) { SoftReference reference = (SoftReference) i.next(); ClassLoader processClassLoader = (ClassLoader) reference.get(); // reference may have been cleared already if (processClassLoader == null) { // remove cleared reference i.remove(); } // process class loader may have a different parent else if (processClassLoader.getParent() == parentClassLoader) { return processClassLoader; } } } return null; } private void putProcessClassLoader(Long processDefinitionKey, ClassLoader processClassLoader) { List referenceList = (List) classLoaderRefs.get(processDefinitionKey); if (referenceList == null) { referenceList = new ArrayList(); classLoaderRefs.put(processDefinitionKey, referenceList); } referenceList.add(new SoftReference(processClassLoader)); } }