com.google.gdt.eclipse.designer.hosted.classloader.GWTSharedClassLoader.java Source code

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Here is the source code for com.google.gdt.eclipse.designer.hosted.classloader.GWTSharedClassLoader.java

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/*******************************************************************************
 * Copyright 2011 Google Inc. All Rights Reserved.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * 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 com.google.gdt.eclipse.designer.hosted.classloader;

import com.google.common.collect.Iterators;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.gdt.eclipse.designer.hosted.IModuleDescription;

import org.apache.commons.collections.CollectionUtils;

import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * The {@link ClassLoader} for gwt-user classes and project classes.
 * 
 * @author mitin_aa
 * @author scheglov_ke
 * @coverage gwtHosted
 */
public final class GWTSharedClassLoader extends URLClassLoader {
    private class State {
        IModuleDescription activeModule;
        ClassLoader activeLoader;
        Map<IModuleDescription, ClassLoader> loaders = Maps.newHashMap();
    }

    private final ThreadLocal<State> stateTL = new ThreadLocal<State>() {
        @Override
        protected State initialValue() {
            return new State();
        }
    };

    ////////////////////////////////////////////////////////////////////////////
    //
    // Constructor
    //
    ////////////////////////////////////////////////////////////////////////////
    public GWTSharedClassLoader(ClassLoader parent, URL[] urls) throws Exception {
        super(urls, parent);
    }

    ////////////////////////////////////////////////////////////////////////////
    //
    // Access
    //
    ////////////////////////////////////////////////////////////////////////////
    /**
     * Adds the {@link IModuleDescription} to this class loader and sets it as active to resources
     * from it. If the project has been already added just sets it as active.
     */
    public void setActiveProject(IModuleDescription module) throws Exception {
        State state = stateTL.get();
        if (state.loaders.get(module) == null) {
            state.loaders.put(module, module.getClassLoader());
        }
        state.activeModule = module;
        state.activeLoader = state.loaders.get(module);
    }

    ////////////////////////////////////////////////////////////////////////////
    //
    // Disposing
    //
    ////////////////////////////////////////////////////////////////////////////
    /**
     * Frees any used resources.
     */
    public void dispose(IModuleDescription module) {
        State state = stateTL.get();
        state.loaders.remove(state.activeModule);
        if (state.activeModule == module) {
            state.activeModule = null;
        }
    }

    ////////////////////////////////////////////////////////////////////////////
    //
    // Loading
    //
    ////////////////////////////////////////////////////////////////////////////
    @Override
    public URL[] getURLs() {
        List<URL> urls = Lists.newArrayList();
        CollectionUtils.addAll(urls, super.getURLs());
        try {
            URL[] moduleURLs = stateTL.get().activeModule.getURLs();
            CollectionUtils.addAll(urls, moduleURLs);
        } catch (Throwable e) {
        }
        return urls.toArray(new URL[urls.size()]);
    }

    ////////////////////////////////////////////////////////////////////////////
    //
    // Resources
    //
    ////////////////////////////////////////////////////////////////////////////
    @Override
    public Enumeration<URL> findResources(String name) throws IOException {
        final Enumeration<URL> superResources = super.findResources(name);
        final Enumeration<URL> moduleResources = stateTL.get().activeLoader.getResources(name);
        Iterator<URL> allResources = Iterators.concat(Iterators.forEnumeration(superResources),
                Iterators.forEnumeration(moduleResources));
        return Iterators.asEnumeration(allResources);
    }

    @Override
    public URL findResource(String name) {
        URL url = super.findResource(name);
        if (url != null) {
            return url;
        }
        return stateTL.get().activeLoader.getResource(name);
    }
}