001/*
002 * Units of Measurement API
003 * Copyright (c) 2014-2015, Jean-Marie Dautelle, Werner Keil, V2COM.
004 *
005 * All rights reserved.
006 *
007 * Redistribution and use in source and binary forms, with or without modification,
008 * are permitted provided that the following conditions are met:
009 *
010 * 1. Redistributions of source code must retain the above copyright notice,
011 *    this list of conditions and the following disclaimer.
012 *
013 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
014 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
015 *
016 * 3. Neither the name of JSR-363 nor the names of its contributors may be used to endorse or promote products
017 *    derived from this software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
020 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
021 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
022 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
023 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
026 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
028 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package javax.measure.spi;
031
032import java.util.List;
033
034/**
035 * This class models the component to managing the lifecycle of the
036 * Unit and Quantity services.
037 * 
038 * @author Werner Keil
039 */
040public interface ServiceProvider {
041
042    /**
043     * This method allows to define a priority for a registered ServiceProvider instance. When multiple providers are
044     * registered in the system the provider with the highest priority value is taken.
045     *
046     * @return the provider's priority (default is 0).
047     */
048    public int getPriority();
049
050    /**
051     * Access a list of services, given its type. The bootstrap mechanism should
052     * order the instance for precedence, hereby the most significant should be
053     * first in order. If no such services are found, an empty list should be
054     * returned.
055     *
056     * @param serviceType
057     *            the service type.
058     * @return The instance to be used, never {@code null}
059     */
060    <T> List<T> getServices(Class<T> serviceType);
061
062    /**
063     * Access a single service, given its type. The bootstrap mechanism should
064     * order the instance for precedence, hereby the most significant should be
065     * first in order and returned. If no such services are found, null is
066     * returned.
067     *
068     * @param serviceType the service type.
069     * @return The instance, (with highest precedence) or {@code null}, if no such service is available.
070     */
071    <T> T getService(Class<T> serviceType);
072}