org.eclipse.emf.teneo.classloader.ClassClassLoaderStrategy.java Source code

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Here is the source code for org.eclipse.emf.teneo.classloader.ClassClassLoaderStrategy.java

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/**
 * <copyright>
 *
 * Copyright (c) 2005, 2006, 2007, 2008 Springsite BV (The Netherlands) and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Martin Taal - Initial API and implementation
 *
 * </copyright>
 *
 * $Id: ClassClassLoaderStrategy.java,v 1.6 2009/03/30 07:53:05 mtaal Exp $
 */

package org.eclipse.emf.teneo.classloader;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Just returns the passed class loader.
 * 
 * @author <a href="mailto:mtaal@elver.org">Martin Taal</a>
 * @version $Revision: 1.6 $
 */

public class ClassClassLoaderStrategy implements ClassLoaderStrategy {
    /** The logger */
    private static Log log = LogFactory.getLog(ClassClassLoaderStrategy.class);

    /** The caller resolver */
    private static CallerResolver callerResolver;

    // Robust way of creating of the caller resolver
    static {
        try {
            // This can fail if the current SecurityManager does not allow
            // RuntimePermission ("createSecurityManager"):
            callerResolver = new CallerResolver();
        } catch (SecurityException se) {
            // set callerResolver to null and log
            log.error("Class class loader resolver could not be created because of SecurityException "
                    + " just using the class loader of the classclassloader class, error msg: " + se.getMessage(),
                    se);
            callerResolver = null;
        }
    }

    /**
     * Indexes into the current method call context with a given offset.
     */
    private static Class<?> getCallerClass(int callerOffset) {
        if (callerResolver == null) {
            return ClassClassLoaderStrategy.class;
        }
        return callerResolver.getClassContext()[callerOffset];
    }

    /**
     * Based on examples in
     * http://www.javaworld.com/javaworld/javaqa/2003-06/01-qa-0606-load-p2.html
     * 
     * A helper class to get the call context. It subclasses SecurityManager to make
     * getClassContext() accessible. An instance of CallerResolver only needs to be created, not
     * installed as an actual security manager.
     */
    private static final class CallerResolver extends SecurityManager {
        protected Class<?>[] getClassContext() {
            final Class<?>[] clsContext = super.getClassContext();
            return clsContext;
        }
    }

    /**
     * Just returns the classClassLoader
     */
    public ClassLoader getClassLoader() {
        /*
         * 0: SecurityManager.getClassContext 1: getClassContext 2: getCallerClass 3: getClassLoader
         * 4: ClassLoaderResolver.getClassLoader 5: app class
         */
        final Class<?> clazz = getCallerClass(5);
        return clazz.getClassLoader();
    }
}