| /******************************************************************************* |
| * Copyright (c) 2003, 2013 IBM Corporation and others. |
| * |
| * This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License 2.0 |
| * which accompanies this distribution, and is available at |
| * https://www.eclipse.org/legal/epl-2.0/ |
| * |
| * SPDX-License-Identifier: EPL-2.0 |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| |
| package org.eclipse.osgi.internal.serviceregistry; |
| |
| import org.eclipse.osgi.internal.framework.BundleContextImpl; |
| import org.eclipse.osgi.internal.messages.Msg; |
| import org.osgi.framework.ServiceException; |
| |
| /** |
| * This class represents the use of a service by a bundle. One is created for each |
| * service acquired by a bundle. |
| * |
| * <p> |
| * This class manages a singleton service. |
| * |
| * @ThreadSafe |
| */ |
| public class ServiceUse<S> { |
| /** ServiceDescription of the registered service */ |
| final ServiceRegistrationImpl<S> registration; |
| |
| /** bundle's use count for this service */ |
| /* @GuardedBy("this") */ |
| private int useCount; |
| |
| /** |
| * Constructs a service use encapsulating the service object. |
| * |
| * @param context bundle getting the service |
| * @param registration ServiceRegistration of the service |
| */ |
| ServiceUse(BundleContextImpl context, ServiceRegistrationImpl<S> registration) { |
| this.useCount = 0; |
| this.registration = registration; |
| } |
| |
| /** |
| * Get a service's service object and increment the use count. |
| * |
| * @return The service object. |
| */ |
| /* @GuardedBy("this") */ |
| S getService() { |
| assert Thread.holdsLock(this); |
| incrementUse(); |
| return registration.getServiceObject(); |
| } |
| |
| /** |
| * Unget a service's service object. |
| * |
| * <p> |
| * Decrements the use count if the service was being used. |
| * |
| * @return true if the service was ungotten; otherwise false. |
| */ |
| /* @GuardedBy("this") */ |
| boolean ungetService() { |
| assert Thread.holdsLock(this); |
| if (!inUse()) { |
| return false; |
| } |
| decrementUse(); |
| return true; |
| } |
| |
| /** |
| * Return the service object for this service use. |
| * |
| * @return The service object. |
| */ |
| /* @GuardedBy("this") */ |
| S getCachedService() { |
| return registration.getServiceObject(); |
| } |
| |
| /** |
| * Get a new service object for the service. |
| * |
| * <p> |
| * By default, this returns the result of {@link #getService()}. |
| * |
| * @return The service object. |
| */ |
| /* @GuardedBy("this") */ |
| S newServiceObject() { |
| return getService(); |
| } |
| |
| /** |
| * Release a service object for the service. |
| * |
| * <p> |
| * By default, this returns the result of {@link #ungetService()}. |
| * |
| * @param service The service object to release. |
| * @return true if the service was released; otherwise false. |
| * @throws IllegalArgumentException If the specified service was not |
| * provided by this object. |
| */ |
| /* @GuardedBy("this") */ |
| boolean releaseServiceObject(final S service) { |
| if ((service == null) || (service != getCachedService())) { |
| throw new IllegalArgumentException(Msg.SERVICE_OBJECTS_UNGET_ARGUMENT_EXCEPTION); |
| } |
| return ungetService(); |
| } |
| |
| /** |
| * Release all uses of the service and reset the use count to zero. |
| */ |
| /* @GuardedBy("this") */ |
| void release() { |
| assert Thread.holdsLock(this); |
| resetUse(); |
| } |
| |
| /** |
| * Is this service use using any services? |
| * |
| * @return true if no services are being used and this service use can be discarded. |
| */ |
| /* @GuardedBy("this") */ |
| boolean isEmpty() { |
| assert Thread.holdsLock(this); |
| return !inUse(); |
| } |
| |
| /** |
| * Is the use count non zero? |
| * |
| * @return true if the use count is greater than zero. |
| */ |
| /* @GuardedBy("this") */ |
| boolean inUse() { |
| return useCount > 0; |
| } |
| |
| /** |
| * Incrementing the use count. |
| */ |
| /* @GuardedBy("this") */ |
| void incrementUse() { |
| if (useCount == Integer.MAX_VALUE) { |
| throw new ServiceException(Msg.SERVICE_USE_OVERFLOW); |
| } |
| useCount++; |
| } |
| |
| /** |
| * Decrementing the use count. |
| */ |
| /* @GuardedBy("this") */ |
| void decrementUse() { |
| assert inUse(); |
| useCount--; |
| } |
| |
| /** |
| * Reset the use count to zero. |
| */ |
| /* @GuardedBy("this") */ |
| void resetUse() { |
| useCount = 0; |
| } |
| } |