de.micromata.genome.gwiki.plugin.CombinedClassLoader.java Source code

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Here is the source code for de.micromata.genome.gwiki.plugin.CombinedClassLoader.java

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//
// Copyright (C) 2010-2016 Roger Rene Kommer & Micromata GmbH
//
// Licensed 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 de.micromata.genome.gwiki.plugin;

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

import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.iterators.IteratorEnumeration;

/**
 * @author Roger Rene Kommer (r.kommer@micromata.de)
 * 
 */
public class CombinedClassLoader extends URLClassLoader {
    private List<ClassLoader> parents = new ArrayList<ClassLoader>();

    public CombinedClassLoader(ClassLoader... parentsClassLoaders) {
        super(new URL[0]);
        for (ClassLoader cl : parentsClassLoaders) {
            addParent(cl);
        }
    }

    public CombinedClassLoader(List<ClassLoader> parentsClassLoaders) {
        super(new URL[0]);
        for (ClassLoader cl : parentsClassLoaders) {
            addParent(cl);
        }
    }

    public boolean containsClassLoader(ClassLoader other) {
        for (ClassLoader cl : parents)
            if (cl == other)
                return true;
        return false;
    }

    /**
     * Fuegt den ClassLoader hinzu, wenn er nicht bereits vorhanden ist
     * 
     * @param cl Der neue ClassLoader
     */
    public void addParent(ClassLoader cl) {
        if (cl != null && containsClassLoader(cl) == false) {
            parents.add(cl);

        }
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        for (ClassLoader cl : parents) {
            try {
                Class<?> ret = cl.loadClass(name);
                if (ret != null) {
                    return ret;
                }
            } catch (ClassNotFoundException cnf) {
                // ignore
            }
        }
        // the parent will do it.
        return super.findClass(name);
    }

    /**
     * Returns the search path of URLs for loading classes and resources. This includes the original list of URLs specified to the
     * constructor, along with any URLs subsequently appended by the addURL() method.
     */
    @Override
    public URL[] getURLs() {
        return super.getURLs();

    }

    @Override
    public URL findResource(String name) {
        for (ClassLoader cl : parents) {
            URL resource = cl.getResource(name);
            if (resource != null)
                return resource;
        }
        return null;
        // return super.findResource(name);
    }

    @Override
    public URL getResource(String name) {
        for (ClassLoader cl : parents) {
            URL resource = cl.getResource(name);
            if (resource != null)
                return resource;
        }
        // return super.getResource(name);
        return null;
    }

    @Override
    public InputStream getResourceAsStream(String name) {
        for (ClassLoader cl : parents) {
            InputStream resource = cl.getResourceAsStream(name);
            if (resource != null)
                return resource;
        }
        return null;
    }

    @Override
    public Enumeration<URL> findResources(String name) throws IOException {
        List<URL> res = new ArrayList<URL>();
        for (ClassLoader cl : parents) {
            Enumeration<URL> resource = cl.getResources(name);
            CollectionUtils.addAll(res, resource);
        }
        return new IteratorEnumeration<URL>(res.iterator());
    }

    @Override
    public Enumeration<URL> getResources(String name) throws IOException {
        return findResources(name);

    }

    @Override
    protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
        return super.loadClass(name, resolve);
    }

    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        for (ClassLoader cl : parents) {
            try {
                Class<?> cls = cl.loadClass(name);
                return cls;
            } catch (ClassNotFoundException ign) {
            } catch (NoClassDefFoundError ign2) {

            }

        }
        throw new ClassNotFoundException(name);
    }

    @Override
    protected String findLibrary(String libname) {
        return super.findLibrary(libname);
    }

    public List<ClassLoader> getParents() {
        return parents;
    }

    public void setParents(List<ClassLoader> parents) {
        this.parents = parents;
    }
}