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/*
* $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.
*
* <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 extends 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 boolean 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);
}
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