/* * $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. */ package org.osgi.framework; /** * A reference to a service. * *

* The Framework returns ServiceReference objects from the * BundleContext.getServiceReference and * BundleContext.getServiceReferences methods. *

* A ServiceReference object may be shared between bundles and * can be used to examine the properties of the service and to get the service * object. *

* Every service registered in the Framework has a unique * ServiceRegistration object and may have multiple, distinct * ServiceReference objects referring to it. * ServiceReference objects associated with a * ServiceRegistration object have the same hashCode * and are considered equal (more specifically, their equals() * method will return true when compared). *

* If the same service object is registered multiple times, * ServiceReference objects associated with different * ServiceRegistration objects are not equal. * * @see BundleContext#getServiceReference * @see BundleContext#getServiceReferences * @see BundleContext#getService * @ThreadSafe * @version $Revision: 1.20 $ */ public interface ServiceReference extends Comparable { /** * Returns the property value to which the specified property key is mapped * in the properties Dictionary object of the service * referenced by this ServiceReference object. * *

* Property keys are case-insensitive. * *

* This method must continue to return property values after the service has * been unregistered. This is so references to unregistered services (for * example, ServiceReference objects stored in the log) can * still be interrogated. * * @param key The property key. * @return The property value to which the key is mapped; null * if there is no property named after the key. */ public Object getProperty(String key); /** * Returns an array of the keys in the properties Dictionary * object of the service referenced by this ServiceReference * object. * *

* This method will continue to return the keys after the service has been * unregistered. This is so references to unregistered services (for * example, ServiceReference objects stored in the log) can * still be interrogated. * *

* This method is case-preserving ; this means that every key in the * returned array must have the same case as the corresponding key in the * properties Dictionary 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 * ServiceReference object. * *

* This method must return null 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 * ServiceReference object; null 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 * ServiceReference 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 ServiceReference object is greater than * zero; null 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 * ServiceReference and the specified bundle use the same * source for the package of the specified class name. *

* This method performs the following checks: *

    *
  1. Get the package name from the specified class name.
    2. *
  2. For the bundle that registered the service referenced by this * ServiceReference (registrant bundle); find the source for * the package. If no source is found then return true if the * registrant bundle is equal to the specified bundle; otherwise return * false.
    3. *
  3. If the package source of the registrant bundle is equal to the * package source of the specified bundle then return true; * otherwise return false.
    4. *
* * @param bundle The Bundle object to check. * @param className The class name to check. * @return true if the bundle which registered the service * referenced by this ServiceReference and the * specified bundle use the same source for the package of the * specified class name. Otherwise false is returned. * * @since 1.3 */ public boolean isAssignableTo(Bundle bundle, String className); /** * Compares this ServiceReference with the specified * ServiceReference for order. * *

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