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Unit Standard (JSR 363) Reference Implementation.
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/*
 * Units of Measurement Reference Implementation
 * Copyright (c) 2005-2015, Jean-Marie Dautelle, Werner Keil, V2COM.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of JSR-363 nor the names of its contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tec.units.ri.internal;

import static java.util.logging.Level.WARNING;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.logging.Logger;

import javax.measure.spi.ServiceProvider;

/**
 * This class implements the {@link ServiceProvider} interface and hereby uses the JDK
 * {@link java.util.ServiceLoader} to load the services required.
 *
 * @author Werner Keil
 */
public class RIServiceProvider implements ServiceProvider {
    /** List of services loaded, per class. */
    private final Map> servicesLoaded = new HashMap>();
    
    @Override
    public int getPriority() {
        return 10;
    }

    /**
     * Loads and registers services.
     *
     * @param serviceType
     *            The service type.
     * @param 
     *            the concrete type.
     * @return the items found, never {@code null}.
     */
    @Override
    public  List getServices(final Class serviceType) {
        @SuppressWarnings("unchecked")
        List found = (List) servicesLoaded.get(serviceType);
        if (found != null) {
            return found;
        }

        return loadServices(serviceType);
    }

    @Override
    public  T getService(Class serviceType) {
        List servicesFound = getServices(serviceType);
        if(servicesFound.isEmpty()){
            return null;
        }
        return servicesFound.get(0);
    }

    /**
     * Loads and registers services.
     *
     * @param   serviceType  The service type.
     * @param             the concrete type.
     *
     * @return  the items found, never {@code null}.
     */
    private  List loadServices(final Class serviceType) {
        final List services = new ArrayList();
        try {
            for (T t : ServiceLoader.load(serviceType)) {
                services.add(t);
            }
            if (!servicesLoaded.containsKey(serviceType)) {
            	final List previousServices = (List) servicesLoaded.put(serviceType, (List