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/*
 * 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.instrument.classloading;

import java.lang.instrument.ClassFileTransformer;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;

import org.jboss.classloader.spi.ClassLoaderPolicy;
import org.jboss.classloader.spi.base.BaseClassLoader;
import org.jboss.util.loading.Translator;
import org.springframework.util.Assert;
import org.springframework.instrument.classloading.SimpleThrowawayClassLoader;

/**
 * Reflective wrapper around a JBoss5 class loader. Used to
 * encapsulate the classloader-specific methods (discovered and
 * called through reflection) from the load-time weaver.
 *
 * @author Ales Justin
 */
public abstract class JBoss5ClassLoader extends ReflectionHelper {

    private final BaseClassLoader classLoader;

    private ClassLoaderPolicy policy;

    protected JBoss5ClassLoader(BaseClassLoader classLoader) {
        Assert.notNull(classLoader, "ClassLoader must not be null");
        this.classLoader = classLoader;

        try {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                AccessController.doPrivileged(new InstantiationAction());
            } else {
                doInstantiate();
            }
        } catch (Exception e) {
            throw new IllegalStateException("Could not initialize JBoss ClassLoader because JBoss5 API classes are not available", e);
        }
    }

    /**
     * Get the policy.
     *
     * @return the policy
     */
    protected ClassLoaderPolicy getPolicy() {
        return policy;
    }

    /**
     * Do instantiate method, variables.
     *
     * @throws Exception for any error
     */
    private void doInstantiate() throws Exception {
        Method getPolicy = getMethod(BaseClassLoader.class, "getPolicy");
        policy = invokeMethod(getPolicy, classLoader, ClassLoaderPolicy.class);
        fallbackStrategy();
    }

    /**
     * The fallback strategy.
     *
     * @throws Exception for any error
     */
    protected void fallbackStrategy() throws Exception {
    }

    public void addTransformer(ClassFileTransformer transformer) {
        Assert.notNull(transformer, "ClassFileTransformer must not be null");
        Translator translator = new ClassFileTransformer2Translator(transformer);
        addTranslator(translator);
    }

    /**
     * Add the translator.
     *
     * @param translator the translator
     */
    protected abstract void addTranslator(Translator translator);

    public ClassLoader getInternalClassLoader() {
        return classLoader;
    }

    public ClassLoader getThrowawayClassLoader() {
        return new SimpleThrowawayClassLoader(classLoader);
    }

    /**
     * Instantiation action.
     */
    private class InstantiationAction implements PrivilegedExceptionAction