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/*
* Copyright (c) OSGi Alliance (2011, 2012). 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.hooks.resolver;
import java.util.Collection;
import org.osgi.framework.Bundle;
import org.osgi.framework.wiring.BundleRevision;
import org.osgi.framework.wiring.FrameworkWiring;
/**
* OSGi Framework Resolver Hook Factory Service.
*
* <p>
* Bundles registering this service will be called by the framework during a
* bundle resolver process to obtain a {@link ResolverHook resolver hook}
* instance which will be used for the duration of a resolve process.
*
* @ThreadSafe
* @see ResolverHook
* @version $Id: e0a2f3ad081c31bbb682fa366c15a3080bf6da2b $
*/
public interface ResolverHookFactory {
/**
* This method is called by the framework each time a resolve process begins
* to obtain a {@link ResolverHook resolver hook} instance. This resolver
* hook instance will be used for the duration of the resolve process. At
* the end of the resolve process the method {@link ResolverHook#end()} must
* be called by the framework and the framework must not hold any references
* of the resolver hook instance.
* <p>
* The triggers represent the collection of bundles which triggered the
* resolve process. This collection may be empty if the triggers cannot be
* determined by the framework. In most cases the triggers can easily be
* determined. Calling certain methods on {@link Bundle bundle} when a
* bundle is in the {@link Bundle#INSTALLED INSTALLED} state will cause the
* framework to begin a resolve process in order to resolve the bundle. The
* following methods will start a resolve process in this case:
* <ul>
* <li>{@link Bundle#start() start}</li>
* <li>{@link Bundle#loadClass(String) loadClass}</li>
* <li>{@link Bundle#findEntries(String, String, boolean) findEntries}</li>
* <li>{@link Bundle#getResource(String) getResource}</li>
* <li>{@link Bundle#getResources(String) getResources}</li>
* </ul>
* In such cases the collection will contain the single bundle which the
* framework is trying to resolve. Other cases will cause multiple bundles
* to be included in the trigger bundles collection. When
* {@link FrameworkWiring#resolveBundles(Collection) resolveBundles} is
* called the collection of triggers must include all the current bundle
* revisions for bundles passed to resolveBundles which are in the
* {@link Bundle#INSTALLED INSTALLED} state.
* <p>
* When
* {@link FrameworkWiring#refreshBundles(Collection, org.osgi.framework.FrameworkListener...)}
* is called the collection of triggers is determined with the following
* steps:
* <ul>
* <li>If the collection of bundles passed is null then
* {@link FrameworkWiring#getRemovalPendingBundles()} is called to get the
* initial collection of bundles.</li>
* <li>The equivalent of calling
* {@link FrameworkWiring#getDependencyClosure(Collection)} is called with
* the initial collection of bundles to get the dependency closure
* collection of the bundles being refreshed.</li>
* <li>Remove any non-active bundles from the dependency closure collection.
* </li>
* <li>For each bundle remaining in the dependency closure collection get
* the current bundle revision and add it to the collection of triggers.</li>
* </ul>
* <p>
* As described above, a resolve process is typically initiated as a result
* of calling API that causes the framework to attempt to resolve one or
* more bundles. The framework is free to start a resolve process at any
* time for reasons other than calls to framework API. For example, a
* resolve process may be used by the framework for diagnostic purposes and
* result in no bundles actually becoming resolved at the end of the
* process. Resolver hook implementations must be prepared for resolve
* processes that are initiated for other reasons besides calls to framework
* API.
*
* @param triggers an unmodifiable collection of bundles which triggered the
* resolve process. This collection may be empty if the collection of
* trigger bundles cannot be determined.
* @return a resolver hook instance to be used for the duration of the
* resolve process. A {@code null} value may be returned which
* indicates this resolver hook factory abstains from the resolve
* process.
*/
ResolverHook begin(Collection<BundleRevision> triggers);
}
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