LoadableExtensionLoader.java

/*
 * JBoss, Home of Professional Open Source
 * Copyright 2011 Red Hat Inc. and/or its affiliates and other contributors
 * as indicated by the @authors tag. All rights reserved.
 * See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * 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 org.jboss.arquillian.core.impl.loadable;

import java.util.Collection;
import java.util.Collections;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jboss.arquillian.core.api.Injector;
import org.jboss.arquillian.core.api.Instance;
import org.jboss.arquillian.core.api.InstanceProducer;
import org.jboss.arquillian.core.api.annotation.ApplicationScoped;
import org.jboss.arquillian.core.api.annotation.Inject;
import org.jboss.arquillian.core.api.annotation.Observes;
import org.jboss.arquillian.core.spi.ExtensionLoader;
import org.jboss.arquillian.core.spi.LoadableExtension;
import org.jboss.arquillian.core.spi.LoadableExtension.ExtensionBuilder;
import org.jboss.arquillian.core.spi.ServiceLoader;
import org.jboss.arquillian.core.spi.context.Context;
import org.jboss.arquillian.core.spi.event.ManagerProcessing;

/**
 * LoadableExtensionLoader
 *
 * @author <a href="mailto:aslak@redhat.com">Aslak Knutsen</a>
 * @version $Revision: $
 */
public class LoadableExtensionLoader {
    private static Logger log = Logger.getLogger(LoadableExtensionLoader.class.getName());
    private static Level level = Level.FINER;

    @Inject
    private Instance<Injector> injector;

    @Inject
    @ApplicationScoped
    private InstanceProducer<ServiceLoader> serviceLoaderProducer;

    private JavaSPIExtensionLoader serviceLoader;

    public LoadableExtensionLoader() {
        this(new JavaSPIExtensionLoader());
    }

    LoadableExtensionLoader(JavaSPIExtensionLoader serviceLoader) {
        this.serviceLoader = serviceLoader;
    }

    public void load(@Observes final ManagerProcessing event) {
        ExtensionLoader extensionLoader = locateExtensionLoader();

        final ServiceRegistry registry = new ServiceRegistry(injector.get(), extensionLoader.loadVetoed());

        Collection<LoadableExtension> extensions = extensionLoader.load();

        for (LoadableExtension extension : extensions) {
            log.log(level, "extension: {0}", new Object[] {extension.getClass().getSimpleName()});
            extension.register(new ExtensionBuilder() {
                @Override
                public <T> ExtensionBuilder service(Class<T> service, Class<? extends T> impl) {
                    log.log(level, "\tservice: {0} - {1}", new Object[] {service, impl});
                    registry.addService(service, impl);
                    return this;
                }

                @Override
                public <T> ExtensionBuilder override(Class<T> service, Class<? extends T> oldServiceImpl,
                    Class<? extends T> newServiceImpl) {
                    log.log(level, "\toverride: {0} overrides {1} for {2}",
                        new Object[] {newServiceImpl, oldServiceImpl, service});
                    registry.overrideService(service, oldServiceImpl, newServiceImpl);
                    return this;
                }

                @Override
                public ExtensionBuilder observer(Class<?> handler) {
                    log.log(level, "\tobserver: {0}", new Object[] {handler});
                    event.observer(handler);
                    return this;
                }

                @Override
                public ExtensionBuilder context(Class<? extends Context> context) {
                    log.log(level, "\tcontext: {0}", new Object[] {context});
                    event.context(context);
                    return this;
                }
            });
        }
        serviceLoaderProducer.set(registry.getServiceLoader());
    }

    /**
     * Some environments need to handle their own ExtensionLoading and can't rely on Java's META-INF/services approach.
     *
     * @return configured ExtensionLoader if found or defaults to JavaSPIServiceLoader
     */
    private ExtensionLoader locateExtensionLoader() {
        Collection<ExtensionLoader> loaders = Collections.emptyList();
        if (SecurityActions.getThreadContextClassLoader() != null) {
            loaders = serviceLoader.all(SecurityActions.getThreadContextClassLoader(), ExtensionLoader.class);
        }
        if (loaders.size() == 0) {
            loaders = serviceLoader.all(LoadableExtensionLoader.class.getClassLoader(), ExtensionLoader.class);
        }
        if (loaders.size() > 1) {
            throw new RuntimeException("Multiple ExtensionLoader's found on classpath: " + toString(loaders));
        }
        if (loaders.size() == 1) {
            return loaders.iterator().next();
        }
        return serviceLoader;
    }

    private String toString(Collection<ExtensionLoader> loaders) {
        StringBuilder sb = new StringBuilder();
        for (ExtensionLoader loader : loaders) {
            sb.append(loader.getClass().getName()).append(", ");
        }
        return sb.toString();
    }
}