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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.

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/*
 * Copyright (c) OSGi Alliance (2000, 2019). 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;

import java.util.Dictionary;

import org.osgi.annotation.versioning.ProviderType;

/**
 * A reference to a service.
 * 
 * 

 * The Framework returns {@code ServiceReference} objects from the
 * {@code BundleContext.getServiceReference} and
 * {@code BundleContext.getServiceReferences} methods.
 * 

 * A {@code 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
 * {@code ServiceRegistration} object and may have multiple, distinct
 * {@code ServiceReference} objects referring to it. {@code ServiceReference}
 * objects associated with a {@code ServiceRegistration} object have the same
 * {@code hashCode} and are considered equal (more specifically, their
 * {@code equals()} method will return {@code true} when compared).
 * 

 * If the same service object is registered multiple times,
 * {@code ServiceReference} objects associated with different
 * {@code ServiceRegistration} objects are not equal.
 * 
 * @param  Type of Service.
 * @see BundleContext#getServiceReference(Class)
 * @see BundleContext#getServiceReference(String)
 * @see BundleContext#getServiceReferences(Class, String)
 * @see BundleContext#getServiceReferences(String, String)
 * @see BundleContext#getService(ServiceReference)
 * @see BundleContext#getServiceObjects(ServiceReference)
 * @ThreadSafe
 * @author $Id: adb91d7f0922417180e901dc6ec447f467b34921 $
 */
@ProviderType
public interface ServiceReference
		extends Comparable, BundleReference {
	/**
	 * Returns the property value to which the specified property key is mapped
	 * in the properties {@code Dictionary} object of the service referenced by
	 * this {@code 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, {@code 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; {@code null} 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} object
	 * of the service referenced by this {@code 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, {@code 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 {@code Dictionary} that was passed to the
	 * {@link BundleContext#registerService(String[],Object,Dictionary)} or
	 * {@link ServiceRegistration#setProperties(Dictionary)} methods.
	 * 
	 * @return An array of property keys.
	 */
	public String[] getPropertyKeys();

	/**
	 * Returns the bundle that registered the service referenced by this
	 * {@code ServiceReference} object.
	 * 
	 * 

	 * This method must return {@code 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
	 *         {@code ServiceReference} object; {@code null} if that service has
	 *         already been unregistered.
	 * @see BundleContext#registerService(String[],Object,Dictionary)
	 */
	@Override
	public Bundle getBundle();

	/**
	 * Returns the bundles that are using the service referenced by this
	 * {@code 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 {@code ServiceReference} object is greater than zero;
	 *         {@code 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
	 * {@code ServiceReference} and the specified bundle use the same source for
	 * the package of the specified class name.
	 * 

	 * This method performs the following checks:
	 * 
    
	 * 
  1. If the specified bundle is equal to the bundle that registered the
	 * service referenced by this {@code ServiceReference} (registrant bundle)
	 * return {@code true}.
    2. 
	 * 
  2. Get the package name from the specified class name.
    3. 
	 * 
  3. For the specified bundle; find the source for the package. If no
	 * source is found then return {@code true} (use of reflection is assumed by
	 * the specified bundle).
    4. 
	 * 
  4. For the registrant bundle; find the source for the package. If the
	 * package source is found then return {@code true} if the package source
	 * equals the package source of the specified bundle; otherwise return
	 * {@code false}.
    5. 
	 * 
  5. If no package source is found for the registrant bundle then
	 * determine the package source based on the service object. If the service
	 * object is a {@code ServiceFactory} and the factory implementation is not
	 * from the registrant bundle return {@code true}; otherwise attempt to find
	 * the package source based on the service object class. If the package
	 * source is found and is equal to package source of the specified bundle
	 * return {@code true}; otherwise return {@code false}.
    6. 
	 * 

	 * 
	 * @param bundle The {@code Bundle} object to check.
	 * @param className The class name to check.
	 * @return {@code true} if the bundle which registered the service
	 *         referenced by this {@code ServiceReference} and the specified
	 *         bundle use the same source for the package of the specified class
	 *         name. Otherwise {@code false} is returned.
	 * @throws IllegalArgumentException If the specified {@code Bundle} was not
	 *             created by the same framework instance as this
	 *             {@code ServiceReference}.
	 * @since 1.3
	 */
	public boolean isAssignableTo(Bundle bundle, String className);

	/**
	 * Compares this {@code ServiceReference} with the specified
	 * {@code ServiceReference} for order.
	 * 
	 * 

	 * If this {@code ServiceReference} and the specified
	 * {@code ServiceReference} have the same {@link Constants#SERVICE_ID
	 * service id} they are equal. This {@code ServiceReference} is less than
	 * the specified {@code ServiceReference} 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} and
	 * the specified {@code ServiceReference} have the same
	 * {@link Constants#SERVICE_RANKING service ranking}, this
	 * {@code ServiceReference} is less than the specified
	 * {@code ServiceReference} 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} to be compared.
	 * @return Returns a negative integer, zero, or a positive integer if this
	 *         {@code ServiceReference} is less than, equal to, or greater than
	 *         the specified {@code ServiceReference}.
	 * @throws IllegalArgumentException If the specified
	 *         {@code ServiceReference} was not created by the same framework
	 *         instance as this {@code ServiceReference}.
	 * @since 1.4
	 */
	@Override
	public int compareTo(Object reference);

	/**
	 * Returns a copy of the properties of the service referenced by this
	 * {@code ServiceReference} object.
	 * 

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

	 * The returned {@code Dictionary} object:
	 * 
    
	 * 
  • Must map property values by using property keys in a
	 * case-insensitive manner.
    • 
	 * 
  • Must return property keys is a case-preserving manner. This
	 * means that the keys must have the same case as the corresponding key in
	 * the properties {@code Dictionary} that was passed to the
	 * {@link BundleContext#registerService(String[],Object,Dictionary)} or
	 * {@link ServiceRegistration#setProperties(Dictionary)} methods.
    • 
	 * 
  • Is the property of the caller and can be modified by the caller but
	 * any changes are not reflected in the properties of the service.
	 * {@link ServiceRegistration#setProperties(Dictionary)} must be called to
	 * modify the properties of the service.
    • 
	 * 

	 * 
	 * @return A copy of the properties of the service referenced by this
	 *         {@code ServiceReference} object
	 * @since 1.9
	 */
	public Dictionary getProperties();

	/**
	 * Adapt this {@code ServiceReference} object to the specified type.
	 * 

	 * Adapting this {@code ServiceReference} object to the specified type may
	 * require certain checks, including security checks, to succeed. If a check
	 * does not succeed, then this {@code ServiceReference} object cannot be
	 * adapted and {@code null} is returned.
	 * 
	 * @param  The type to which this {@code ServiceReference} object is to
	 *            be adapted.
	 * @param type Class object for the type to which this
	 *            {@code ServiceReference} object is to be adapted.
	 * @return The object, of the specified type, to which this
	 *         {@code ServiceReference} object has been adapted or {@code null}
	 *         if this {@code ServiceReference} object cannot be adapted to the
	 *         specified type.
	 * @throws SecurityException If the caller does not have the appropriate
	 *             {@code AdaptPermission[type,this,ADAPT]}, and the Java
	 *             Runtime Environment supports permissions.
	 * @since 1.10
	 */
	 A adapt(Class type);
}
 















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