IsolatedClassLoader.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.felix.ipojo.manipulator.util;

import java.net.URL;
import java.net.URLClassLoader;
import java.util.HashSet;
import java.util.Set;

/**
 * A classloader used by the {@link org.apache.felix.ipojo.manipulator.util.Classpath}.
 */
public class IsolatedClassLoader
        extends URLClassLoader {
    private final ClassLoader parent = ClassLoader.getSystemClassLoader();

    private final Set<URL> urls = new HashSet<URL>();

    private boolean childDelegation = true;

    private static final URL[] EMPTY_URL_ARRAY = new URL[0];

    public IsolatedClassLoader(ClassLoader parent, boolean childDelegation) {
        super(EMPTY_URL_ARRAY, parent);
        this.childDelegation = childDelegation;
    }

    public IsolatedClassLoader() {
        super(EMPTY_URL_ARRAY, ClassLoader.getSystemClassLoader());
        this.childDelegation  = true;
    }

    public void addURL(URL url) {
        // avoid duplicates
        if (!urls.contains(url)) {
            super.addURL(url);
            urls.add(url);
        }
    }

    public synchronized Class loadClass(String name)
            throws ClassNotFoundException {
        Class c;
        if (childDelegation) {
            c = findLoadedClass(name);

            ClassNotFoundException ex = null;

            if (c == null) {
                try {
                    c = findClass(name);
                } catch (ClassNotFoundException e) {
                    ex = e;
                    if (parent != null) {
                        c = parent.loadClass(name);
                    }
                }
            }

            if (c == null) {
                throw ex;
            }
        } else {
            c = super.loadClass(name);
        }

        return c;
    }
}