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/*
 * 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.flowable.osgi.blueprint;

import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;

public class ClassLoaderWrapper extends ClassLoader {

    private ClassLoader[] parents;

    public ClassLoaderWrapper(ClassLoader... parents) {
        this.parents = parents;
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Override
    protected synchronized Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
        //
        // Check if class is in the loaded classes cache
        //
        Class cachedClass = findLoadedClass(name);
        if (cachedClass != null) {
            if (resolve) {
                resolveClass(cachedClass);
            }
            return cachedClass;
        }

        //
        // Check parent class loaders
        //
        for (int i = 0; i < parents.length; i++) {
            ClassLoader parent = parents[i];
            try {
                Class clazz = parent.loadClass(name);
                if (resolve) {
                    resolveClass(clazz);
                }
                return clazz;
            } catch (ClassNotFoundException ignored) {
                // this parent didn't have the class; try the next one
            }
        }

        throw new ClassNotFoundException(name);
    }

    @Override
    public URL getResource(String name) {
        //
        // Check parent class loaders
        //
        for (int i = 0; i < parents.length; i++) {
            ClassLoader parent = parents[i];
            URL url = parent.getResource(name);
            if (url != null) {
                return url;
            }
        }

        return null;
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Override
    public Enumeration findResources(String name) throws IOException {
        List resources = new ArrayList();

        //
        // Add parent resources
        //
        for (int i = 0; i < parents.length; i++) {
            ClassLoader parent = parents[i];
            List parentResources = Collections.list(parent.getResources(name));
            resources.addAll(parentResources);
        }

        return Collections.enumeration(resources);
    }

}