ServiceRegistryLoader.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.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import org.jboss.arquillian.core.api.Injector;
import org.jboss.arquillian.core.spi.ServiceLoader;

/**
 * MixedServiceLoader
 *
 * @author <a href="mailto:aslak@redhat.com">Aslak Knutsen</a>
 * @version $Revision: $
 */
public class ServiceRegistryLoader implements ServiceLoader {
    private Injector injector;
    private ServiceRegistry registry;

    public ServiceRegistryLoader(Injector injector, ServiceRegistry registry) {
        this.injector = injector;
        this.registry = registry;
    }

    /* (non-Javadoc)
     * @see org.jboss.arquillian.core.spi.ServiceLoader#all(java.lang.Class)
     */
    @Override
    public <T> Collection<T> all(Class<T> serviceClass) {
        List<T> serviceImpls = new ArrayList<T>();
        Set<Class<? extends T>> serviceImplClasses = registry.getServiceImpls(serviceClass);
        for (Class<? extends T> serviceImplClass : serviceImplClasses) {
            T serviceImpl = createServiceInstance(serviceImplClass);
            serviceImpls.add(serviceImpl);
        }
        return serviceImpls;
    }

    /* (non-Javadoc)
     * @see org.jboss.arquillian.core.spi.ServiceLoader#onlyOne(java.lang.Class)
     */
    @Override
    public <T> T onlyOne(Class<T> serviceClass) {
        Collection<T> all = all(serviceClass);
        if (all.size() == 1) {
            return all.iterator().next();
        }
        if (all.size() > 1) {
            throw new IllegalStateException(
                "Multiple service implementations found for " + serviceClass + ". " + toClassString(all));
        }
        return null;
    }

    /* (non-Javadoc)
     * @see org.jboss.arquillian.core.spi.ServiceLoader#onlyOne(java.lang.Class, java.lang.Class)
     */
    @Override
    public <T> T onlyOne(Class<T> serviceClass, Class<? extends T> defaultServiceClass) {
        T one = null;
        try {
            one = onlyOne(serviceClass);
        } catch (Exception e) {
        }

        if (one == null) {
            one = createServiceInstance(defaultServiceClass);
        }
        return one;
    }

    private <T> T createServiceInstance(Class<T> service) {
        T serviceInst = SecurityActions.newInstance(
            service,
            new Class<?>[] {},
            new Object[] {});

        injector.inject(serviceInst);
        return serviceInst;
    }

    private <T> String toClassString(Collection<T> providers) {
        StringBuilder sb = new StringBuilder();
        for (Object provider : providers) {
            sb.append(provider.getClass().getName()).append(", ");
        }
        return sb.subSequence(0, sb.length() - 2).toString();
    }
}