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A feature describes an OSGi system
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
/**
* Defines the interfaces of the JCR SPI (Service Provider Interface).
*
*
* The SPI cuts the JCR stack into two parts:
*
* - Above the SPI an implementation that wishes to expose the JCR API again
* needs to implement the transient item space, the session local namespace
* mapping and various conversions from the value representation in the SPI to
* the resolved values in the JCR API.
* - An implementation of the SPI interfaces has to deal with the persistent
* view of a JCR repository. This includes almost all aspects of the JSR 170
* specification, except the previously stated transient space and the session
* local namespace resolution to prefixes.
*
*
* Observation
* Because one of the goals of this SPI is to make it easier to implement a
* remoting layer using various existing protocols, the observation mechanism
* has been design with this goal in mind. Instead of a listener registration
* with a callback for each event bundle, the SPI uses a polling mechanism
* with a timeout: {@link org.apache.jackrabbit.spi.RepositoryService#getEvents
* RepositoryService.getEvents()}. With every call to this method the
* repository is advised to return the events that occurred since the last
* call. As a reference to the last retrieved
* {@link org.apache.jackrabbit.spi.EventBundle} the
* {@link org.apache.jackrabbit.spi.SessionInfo} contains a bundle identifier
* which is automatically updated on each call to
* RepositoryService.getEvents()
. While this design allows for
* a polling implementation on top of the SPI it is also well suited for a
* listener based observation implementation on top of the SPI. With only
* little thread synchronization overhead events can be acquired using a
* timeout
of {@link java.lang.Long#MAX_VALUE}.
*
* If an SPI implementation does not support observation, the method
* RepositoryService.getEvents()
will always throw an
* {@link javax.jcr.UnsupportedRepositoryOperationException}.
*/
@org.osgi.annotation.versioning.Version("3.0.0")
package org.apache.jackrabbit.spi;