Glassfish example source code file (ACCClassLoader.java)

This example Glassfish source code file (ACCClassLoader.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

accclassloader, accclassloader, class, class, classloader, classnotfoundexception, classnotfoundexception, exception, gfsystemuri, io, list, log, logging, net, network, runtimeexception, string, string, url, util

The Glassfish ACCClassLoader.java source code

/*
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 *
 * Copyright (c) 1997-2010 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:
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 * Version 2] license."  If you don't indicate a single choice of license, a
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 * 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
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 */

package org.glassfish.appclient.client.acc;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.reflect.Field;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author tjquinn
 */
public class ACCClassLoader extends URLClassLoader {

    private static final String AGENT_LOADER_CLASS_NAME =
            "org.glassfish.appclient.client.acc.agent.ACCAgentClassLoader";
    private static ACCClassLoader instance = null;

    private ACCClassLoader shadow = null;

    private boolean shouldTransform = false;
    
    private final List<ClassFileTransformer> transformers =
            Collections.synchronizedList(
                new ArrayList<ClassFileTransformer>());

    public static synchronized ACCClassLoader newInstance(ClassLoader parent,
            final boolean shouldTransform) {
        if (instance != null) {
            throw new IllegalStateException("already set");
        }
        final ClassLoader currentCL = Thread.currentThread().getContextClassLoader();
        ClassLoader parentForACCCL = currentCL;
        final boolean currentCLWasAgentCL = currentCL.getClass().getName().equals(
                    AGENT_LOADER_CLASS_NAME);
        if (currentCLWasAgentCL) {
            parentForACCCL = currentCL.getParent();
        }
        
        instance = new ACCClassLoader(userClassPath(), parentForACCCL, shouldTransform);
        
        if (currentCLWasAgentCL) {
            try {
                adjustACCAgentClassLoaderParent(instance);
            } catch (Exception ex) {
                throw new RuntimeException(ex);
            }
        }

        return instance;
    }

    public static ACCClassLoader instance() {
        return instance;
    }

    private static void adjustACCAgentClassLoaderParent(final ACCClassLoader instance)
            throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
        final ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
        if (systemClassLoader.getClass().getName().equals(AGENT_LOADER_CLASS_NAME)) {
            final Field jwsLoaderParentField = ClassLoader.class.getDeclaredField("parent");
            jwsLoaderParentField.setAccessible(true);
            jwsLoaderParentField.set(systemClassLoader, instance);
            System.setProperty("org.glassfish.appclient.acc.agentLoaderDone", "true");
        
        }
    }
    
    private static URL[] userClassPath() {
        final URI GFSystemURI = GFSystemURI();
        final List<URL> result = classPathToURLs(System.getProperty("java.class.path"));
        for (ListIterator<URL> it = result.listIterator(); it.hasNext();) {
            final URL url = it.next();
            try {
                if (url.toURI().equals(GFSystemURI)) {
                    it.remove();
                }
            } catch (URISyntaxException ex) {
                throw new RuntimeException(ex);
            }
        }

        result.addAll(classPathToURLs(System.getenv("APPCPATH")));

        return result.toArray(new URL[result.size()]);
    }

    private static URI GFSystemURI() {
        try {
            Class agentClass = Class.forName("org.glassfish.appclient.client.acc.agent.AppClientContainerAgent");
            return agentClass.getProtectionDomain().getCodeSource().getLocation().toURI().normalize();
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    private static List<URL> classPathToURLs(final String classPath) {
        if (classPath == null) {
            return Collections.EMPTY_LIST;
        }
        final List<URL> result = new ArrayList();
        try {
            for (String classPathElement : classPath.split(File.pathSeparator)) {
                result.add(new File(classPathElement).toURI().normalize().toURL());
            }
            return result;
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }

    public ACCClassLoader(ClassLoader parent, final boolean shouldTransform) {
        super(new URL[0], parent);
        this.shouldTransform = shouldTransform;
    }
//
//    public ACCClassLoader(URL[] urls) {
//        super(urls);
//    }

    public ACCClassLoader(URL[] urls, ClassLoader parent) {
        super(urls, parent);
    }

//    public ACCClassLoader(URL[] urls, ClassLoader parent, URLStreamHandlerFactory factory) {
//        super(urls, parent, factory);
//    }

    private ACCClassLoader(URL[] urls, ClassLoader parent, boolean shouldTransform) {
        this(urls, parent);
        this.shouldTransform = shouldTransform;
    }
    
    public synchronized void appendURL(final URL url) {
        addURL(url);
        if (shadow != null) {
            shadow.addURL(url);
        }
    }

    public void addTransformer(final ClassFileTransformer xf) {
        transformers.add(xf);
    }

    public void setShouldTransform(final boolean shouldTransform) {
        this.shouldTransform = shouldTransform;
    }

    synchronized ACCClassLoader shadow() {
        if (shadow == null) {
            shadow = new ACCClassLoader( getURLs(), getParent());
            }
        return shadow;
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        if ( ! shouldTransform) {
            return super.findClass(name);
        }
        final ACCClassLoader s = shadow();
        final Class<?> c = s.findClassUnshadowed(name);
        return copyClass(c);
    }

    private Class<?> copyClass(final Class c) throws ClassNotFoundException {
        final String name = c.getName();
        final ProtectionDomain pd = c.getProtectionDomain();
        byte[] bytecode = readByteCode(name);

        for (ClassFileTransformer xf : transformers) {
            try {
                bytecode = xf.transform(this, name, null, pd, bytecode);
            } catch (IllegalClassFormatException ex) {
                throw new ClassNotFoundException(name, ex);
            }
        }
        return defineClass(name, bytecode, 0, bytecode.length, pd);
    }

    private Class<?> findClassUnshadowed(String name) throws ClassNotFoundException {
        return super.findClass(name);
    }

    private byte[] readByteCode(final String className) throws ClassNotFoundException {
        final String resourceName = className.replace('.', '/') + ".class";
        InputStream is = getResourceAsStream(resourceName);
        if (is == null) {
            throw new ClassNotFoundException(className);
        }
        try {
            final ByteArrayOutputStream baos = new ByteArrayOutputStream();
            final byte[] buffer = new byte[8196];
            int bytesRead;
            while ( (bytesRead = is.read(buffer)) != -1) {
                baos.write(buffer, 0, bytesRead);
            }
            return baos.toByteArray();
        } catch (IOException e) {
            throw new ClassNotFoundException(className, e);
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                throw new ClassNotFoundException(className, e);
            }
        }
    }
}