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/*
* Copyright (c) OSGi Alliance (2008, 2009). 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.apache.tuscany.sca.osgi.remoteserviceadmin;
/**
* A white board service that represents a listener for endpoints.
*
* An Endpoint Listener represents a participant in the distributed model that
* is interested in Endpoint Descriptions.
*
* This white board service can be used in many different scenarios. However, the
* primary use case is to allow a remote manager to be informed of End Point
* Descriptions available in the network and inform the network about available
* End Point Descriptions.
*
* Both the network bundle and the manager bundle register an Endpoint
* Listener service. The manager informs the network bundle about End Points
* that it creates. The network bundles then uses a protocol like
* SLP to announce these local end-points to the network.
*
* If the network bundle discovers a new Endpoint through its discovery
* protocol, then it sends an End Point Description to all the End Point
* Listener services that are registered (except its own) that have specified an
* interest in that endpoint.
*
* Endpoint Listener services can express their <i>scope</i> with the service
* property {@link #ENDPOINT_LISTENER_SCOPE}. This service property is a list
* of filters. An Endpoint Description should only be given to a Endpoint
* Listener when there is at least one filter that matches the Endpoint
* Description properties. given to it.
*
* This filter model is quite flexible. For example, a discovery bundle is only
* interested in locally originating Endpoint Descriptions. The following filter
* ensure that it only sees local endpoints.
*
* <pre>
* (org.osgi.framework.uuid=72dc5fd9-5f8f-4f8f-9821-9ebb433a5b72)
* </pre>
*
* In the same vein, a manager that is only interested in remote Endpoint
* Descriptions can use a filter like:
*
* <pre>
* (!(org.osgi.framework.uuid=72dc5fd9-5f8f-4f8f-9821-9ebb433a5b72))
* </pre>
*
* Where in both cases, the given UUID is the UUID of the local framework that
* can be found in the Framework properties.
*
* The Endpoint Listener's scope maps very well to the service hooks. A
* manager can just register all filters found from the Listener Hook as its
* scope. This will automatically provide it with all known endpoints that match
* the given scope, without having to inspect the filter string.
*
* In general, when an Endpoint Description is discovered, it should be
* dispatched to all registered Endpoint Listener services. If a new Endpoint
* Listener is registered, it should be informed about all currently known
* Endpoints that match its scope. If a getter of the Endpoint Listener service
* is unregistered, then all its registered Endpoint Description objects must be
* removed.
*
* The Endpoint Listener models a <i>best effort</i> approach. Participating
* bundles should do their utmost to keep the listeners up to date, but
* implementers should realize that many endpoints come through unreliable
* discovery processes.
*
*
* @ThreadSafe
*/
public interface EndpointListener {
/**
* Specifies the interest of this listener with filters. This listener is
* only interested in Endpoint Descriptions where its properties match the
* given filter. The type of this property must be <code>String+</code>.
*/
String ENDPOINT_LISTENER_SCOPE = "endpoint.listener.scope";
/**
* Register an endpoint with this listener.
*
* If the endpoint matches one of the filters registered with the
* {@link #ENDPOINT_LISTENER_SCOPE} service property then this filter should
* be given as the <code>matchedFilter</code> parameter.
*
* When this service is first registered or it is modified, it should
* receive all known endpoints matching the filter.
*
* @param endpoint
* The Endpoint Description to be published
* @param matchedFilter
* The filter from the {@link #ENDPOINT_LISTENER_SCOPE} that
* matched the endpoint, must not be <code>null</code>.
*/
void endpointAdded(EndpointDescription endpoint, String matchedFilter);
/**
* Remove the registration of an endpoint.
*
* If an endpoint that was registered with the {@link #endpointAdded(EndpointDescription, String)}
* method is no longer available then this method should be called. This
* will remove the endpoint from the listener.
*
* It is not necessary to remove endpoints when the service is unregistered
* or modified in such a way that not all endpoints match the interest
* filter anymore.
*
* @param endpoint
* The Endpoint Description that is no longer valid.
* @param matchedFilter
* The filter from the {@link #ENDPOINT_LISTENER_SCOPE} that
* matched the endpoint, must not be <code>null</code>.
*/
void endpointRemoved(EndpointDescription endpoint, String matchedFilter);
}
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