blueprint-core/src/main/java/org/apache/aries/blueprint/utils/BundleDelegatingClassLoader.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.aries.blueprint.utils;

import java.io.IOException;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;

import org.osgi.framework.Bundle;

/**
 * A ClassLoader delegating to a given OSGi bundle.
 *
 * @version $Rev: 954428 $, $Date: 2010-06-14 13:32:07 +0100 (Mon, 14 Jun 2010) $
 */
public class BundleDelegatingClassLoader extends ClassLoader {

    private final Bundle bundle;
    private final ClassLoader classLoader;

    public BundleDelegatingClassLoader(Bundle bundle) {
        this(bundle, null);
    }

    public BundleDelegatingClassLoader(Bundle bundle, ClassLoader classLoader) {
        this.bundle = bundle;
        this.classLoader = classLoader;
    }

    protected Class findClass(final String name) throws ClassNotFoundException {
        try {
            return AccessController.doPrivileged(new PrivilegedExceptionAction<Class<?>>() {
                public Class<?> run() throws ClassNotFoundException 
                {
                    return bundle.loadClass(name);
                }
            
            });
        } catch (PrivilegedActionException e) {
            Exception cause = e.getException();
          
            if (cause instanceof ClassNotFoundException) throw (ClassNotFoundException)cause;
            else throw (RuntimeException)cause;
        }    
    }

    protected URL findResource(final String name) {
        URL resource = AccessController.doPrivileged(new PrivilegedAction<URL>() {
            public URL run()
            {
                return bundle.getResource(name);
            }
        });        
        if (classLoader != null && resource == null) {
            resource = classLoader.getResource(name);
        }
        return resource;
    }

    protected Enumeration findResources(final String name) throws IOException {
        Enumeration<URL> urls;
        try {
            urls =  AccessController.doPrivileged(new PrivilegedExceptionAction<Enumeration<URL>>() {
                @SuppressWarnings("unchecked")
                public Enumeration<URL> run() throws IOException
                {
                    return (Enumeration<URL>)bundle.getResources(name);
                }
          
            });
        } catch (PrivilegedActionException e) {
            Exception cause = e.getException();
        
            if (cause instanceof IOException) throw (IOException)cause;
            else throw (RuntimeException)cause;
        }
      
        if (urls == null) {
            urls = Collections.enumeration(new ArrayList<URL>());
        }
      
        return urls;    
    }

    protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
        Class clazz;
        try {
            clazz = findClass(name);
        }
        catch (ClassNotFoundException cnfe) {
            if (classLoader != null) {
                try {
                    clazz = classLoader.loadClass(name);
                } catch (ClassNotFoundException e) {
                    throw new ClassNotFoundException(name + " from bundle " + bundle.getBundleId() + " (" + bundle.getSymbolicName() + ")", cnfe);
                }
            } else {
                throw new ClassNotFoundException(name + " from bundle " + bundle.getBundleId() + " (" + bundle.getSymbolicName() + ")", cnfe);
            }
        }
        if (resolve) {
            resolveClass(clazz);
        }
        return clazz;
    }

    public Bundle getBundle() {
        return bundle;
    }
}