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Glassfish example source code file (MaskingClassLoader.java)

This example Glassfish source code file (MaskingClassLoader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Glassfish tags/keywords

classloader, classnotfoundexception, collection, collection, enumeration, io, maskingclassloader, maskingclassloader, net, network, nosuchelementexception, override, override, set, string, string, url, util

The Glassfish MaskingClassLoader.java source code

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2008-2010 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package com.sun.enterprise.glassfish.bootstrap;

import java.io.IOException;
import java.net.URL;
import java.util.*;

/**
 * {@link ClassLoader} that masks a specified set of classes
 * from its parent class loader.
 *
 * <p>
 * This code is used to create an isolated environment.
 *
 * @author Jerome Dochez
 */
public class MaskingClassLoader extends ClassLoader {

    private final Set<String> punchins = new HashSet();
    private final String[] multiples;

    private final boolean useExplicitCallsToFindSystemClass;

    public MaskingClassLoader(ClassLoader parent, Collection<String> punchins, Collection multiples) {
        this(parent, punchins, multiples, true /* use explicit calls to findSystemClass*/);
    }
    /**
     * Creates a new masking class loader letting a set of defined packages be loaded by the parent
     * classloader. Multiples packages can be specified so that only the parent package needs to
     * be provided.
     *
     * @param parent the parent classloader to delegate actual loading from when punchin is allowed
     * @param punchins list of packages allowed to be visible from the parent
     * @param multiples list of parent packages allowed to be visible from the parent class loader
     */
    public MaskingClassLoader(ClassLoader parent, Collection<String> punchins, Collection multiples,
            boolean useExplicitCallsToFindSystemClass) {
        super(parent);
        this.punchins.addAll(punchins);
        this.multiples = multiples.toArray(new String[multiples.size()]);
        this.useExplicitCallsToFindSystemClass = useExplicitCallsToFindSystemClass;
    }

    @Override
    protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {

        // I do not mask java packages, and I only mask javax. stuff for now.
        try {
            if (useExplicitCallsToFindSystemClass) {
                return findSystemClass(name);
            }
        } catch(ClassNotFoundException e) {

        }
        if (isDottedNameLoadableByParent(name)) {
            return super.loadClass(name, resolve);
        }
        throw new ClassNotFoundException(name);
     }

    @Override
    public URL getResource(String name) {
        if (isDottedNameLoadableByParent(resourceToDotted(name))) {
            return super.getResource(name);
        } else {
            return null;
        }
    }

    @Override
    public Enumeration<URL> getResources(String name) throws IOException {
        if (isDottedNameLoadableByParent(resourceToDotted(name))) {
            return super.getResources(name);
        } else {
            return new Enumeration<URL>() {

                @Override
                public boolean hasMoreElements() {
                    return false;
                }

                @Override
                public URL nextElement() {
                    throw new NoSuchElementException();
                }
            };
        }
    }
    
    private String resourceToDotted(String name) {
        if (name.startsWith("/")) {
            name = name.substring(1);
        }
        return name.replace("/", ".");
    }
    
    protected boolean isDottedNameLoadableByParent(final String name) {
        if (!(name.startsWith("javax.") || name.startsWith("org."))) {
            return true;
        }
        final String packageName = name.substring(0, name.lastIndexOf("."));
        if (punchins.contains(packageName)) {
            return true;
        }
        for (String multiple : multiples) {
            if (name.startsWith(multiple)) {
                return true;
            }
        }
        return false;
    }
    
    
}

Other Glassfish examples (source code examples)

Here is a short list of links related to this Glassfish MaskingClassLoader.java source code file:

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