/*
 * $Header: /cvshome/build/org.osgi.framework/src/org/osgi/framework/ServiceReference.java,v 1.20 2007/02/21 16:49:05 hargrave Exp $
 * 
 * Copyright (c) OSGi Alliance (2000, 2007). All Rights Reserved.
 * 
 * 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.
 */

module org.osgi.framework.ServiceReference;
import org.osgi.framework.Bundle;

import java.lang.all;

/**
 * A reference to a service.
 * 
 * <p>
 * The Framework returns <code>ServiceReference</code> objects from the
 * <code>BundleContext.getServiceReference</code> and
 * <code>BundleContext.getServiceReferences</code> methods.
 * <p>
 * A <code>ServiceReference</code> object may be shared between bundles and
 * can be used to examine the properties of the service and to get the service
 * object.
 * <p>
 * Every service registered in the Framework has a unique
 * <code>ServiceRegistration</code> object and may have multiple, distinct
 * <code>ServiceReference</code> objects referring to it.
 * <code>ServiceReference</code> objects associated with a
 * <code>ServiceRegistration</code> object have the same <code>hashCode</code>
 * and are considered equal (more specifically, their <code>equals()</code>
 * method will return <code>true</code> when compared).
 * <p>
 * If the same service object is registered multiple times,
 * <code>ServiceReference</code> objects associated with different
 * <code>ServiceRegistration</code> objects are not equal.
 * 
 * @see BundleContext#getServiceReference
 * @see BundleContext#getServiceReferences
 * @see BundleContext#getService
 * @ThreadSafe
 * @version $Revision: 1.20 $
 */

public interface ServiceReference : Comparable {
    /**
     * Returns the property value to which the specified property key is mapped
     * in the properties <code>Dictionary</code> object of the service
     * referenced by this <code>ServiceReference</code> object.
     * 
     * <p>
     * Property keys are case-insensitive.
     * 
     * <p>
     * This method must continue to return property values after the service has
     * been unregistered. This is so references to unregistered services (for
     * example, <code>ServiceReference</code> objects stored in the log) can
     * still be interrogated.
     * 
     * @param key The property key.
     * @return The property value to which the key is mapped; <code>null</code>
     *         if there is no property named after the key.
     */
    public Object getProperty(String key);

    /**
     * Returns an array of the keys in the properties <code>Dictionary</code>
     * object of the service referenced by this <code>ServiceReference</code>
     * object.
     * 
     * <p>
     * This method will continue to return the keys after the service has been
     * unregistered. This is so references to unregistered services (for
     * example, <code>ServiceReference</code> objects stored in the log) can
     * still be interrogated.
     * 
     * <p>
     * This method is <i>case-preserving </i>; this means that every key in the
     * returned array must have the same case as the corresponding key in the
     * properties <code>Dictionary</code> that was passed to the
     * {@link BundleContext#registerService(String[],Object,java.util.Dictionary)}
     * or {@link ServiceRegistration#setProperties} methods.
     * 
     * @return An array of property keys.
     */
    public String[] getPropertyKeys();

    /**
     * Returns the bundle that registered the service referenced by this
     * <code>ServiceReference</code> object.
     * 
     * <p>
     * This method must return <code>null</code> when the service has been
     * unregistered. This can be used to determine if the service has been
     * unregistered.
     * 
     * @return The bundle that registered the service referenced by this
     *         <code>ServiceReference</code> object; <code>null</code> if
     *         that service has already been unregistered.
     * @see BundleContext#registerService(String[],Object,java.util.Dictionary)
     */
    public Bundle getBundle();

    /**
     * Returns the bundles that are using the service referenced by this
     * <code>ServiceReference</code> object. Specifically, this method returns
     * the bundles whose usage count for that service is greater than zero.
     * 
     * @return An array of bundles whose usage count for the service referenced
     *         by this <code>ServiceReference</code> object is greater than
     *         zero; <code>null</code> if no bundles are currently using that
     *         service.
     * 
     * @since 1.1
     */
    public Bundle[] getUsingBundles();

    /**
     * Tests if the bundle that registered the service referenced by this
     * <code>ServiceReference</code> and the specified bundle use the same
     * source for the package of the specified class name.
     * <p>
     * This method performs the following checks:
     * <ol>
     * <li>Get the package name from the specified class name.</li>
     * <li>For the bundle that registered the service referenced by this
     * <code>ServiceReference</code> (registrant bundle); find the source for
     * the package. If no source is found then return <code>true</code> if the
     * registrant bundle is equal to the specified bundle; otherwise return
     * <code>false</code>.</li>
     * <li>If the package source of the registrant bundle is equal to the
     * package source of the specified bundle then return <code>true</code>;
     * otherwise return <code>false</code>.</li>
     * </ol>
     * 
     * @param bundle The <code>Bundle</code> object to check.
     * @param className The class name to check.
     * @return <code>true</code> if the bundle which registered the service
     *         referenced by this <code>ServiceReference</code> and the
     *         specified bundle use the same source for the package of the
     *         specified class name. Otherwise <code>false</code> is returned.
     * 
     * @since 1.3
     */
    public bool isAssignableTo(Bundle bundle, String className);

    /**
     * Compares this <code>ServiceReference</code> with the specified
     * <code>ServiceReference</code> for order.
     * 
     * <p>
     * If this <code>ServiceReference</code> and the specified
     * <code>ServiceReference</code> have the same
     * {@link Constants#SERVICE_ID service id} they are equal. This
     * <code>ServiceReference</code> is less than the specified
     * <code>ServiceReference</code> if it has a lower
     * {@link Constants#SERVICE_RANKING service ranking} and greater if it has a
     * higher service ranking. Otherwise, if this <code>ServiceReference</code>
     * and the specified <code>ServiceReference</code> have the same
     * {@link Constants#SERVICE_RANKING service ranking}, this
     * <code>ServiceReference</code> is less than the specified
     * <code>ServiceReference</code> if it has a higher
     * {@link Constants#SERVICE_ID service id} and greater if it has a lower
     * service id.
     * 
     * @param reference The <code>ServiceReference</code> to be compared.
     * @return Returns a negative integer, zero, or a positive integer if this
     *         <code>ServiceReference</code> is less than, equal to, or
     *         greater than the specified <code>ServiceReference</code>.
     * @since 1.4
     */
    public int compareTo(Object reference);
}