001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.spi;
018
019 import org.apache.camel.CamelContext;
020 import org.apache.camel.Exchange;
021
022 /**
023 * A specialized {@link org.apache.camel.spi.AggregationRepository} which also supports
024 * optimistic locking.
025 *
026 * If the underlying implementation cannot perform optimistic locking, it should
027 * not implement this interface.
028 *
029 * @see org.apache.camel.processor.aggregate.MemoryAggregationRepository
030 *
031 * @version
032 */
033 public interface OptimisticLockingAggregationRepository extends AggregationRepository {
034
035 /**
036 * {@link Exception} used by an {@code AggregationRepository} to indicate that an optimistic
037 * update error has occurred and that the operation should be retried by the caller.
038 * <p/>
039 */
040 class OptimisticLockingException extends RuntimeException {
041 private static final long serialVersionUID = 1L;
042 }
043
044 /**
045 * Add the given {@link org.apache.camel.Exchange} under the correlation key.
046 * <p/>
047 * Will perform optimistic locking to replace expected existing exchange with the new supplied exchange.
048 * <p/>
049 * If the {@code oldExchange} is null the underlying implementation is to assume this is the very first Exchange for the
050 * supplied correlation key. When the implementation comes to store to the Exchange if there is already an existing
051 * Exchange present for this correlation key the implementation should throw an OptimisticLockingException.
052 * <p/>
053 * If the {@code oldExchange} is not null the underlying implementation should use it to compare with the existing exchange
054 * when doing an atomic compare-and-set/swap operation.
055 * <p/>
056 * The implementation may achieve this by storing a version identifier in the Exchange as a parameter. Set before
057 * returning from {@link AggregationRepository#get(org.apache.camel.CamelContext, String)}} and retrieved from the
058 * exchange when passed to {@link AggregationRepository#add(org.apache.camel.CamelContext, String, org.apache.camel.Exchange)}.
059 * <p/>
060 * Note: The {@link org.apache.camel.processor.aggregate.MemoryAggregationRepository} is an exception to this recommendation.
061 * It uses the {@code oldExchange}'s Object identify to perform it's compare-and-set/swap operation, instead of a version
062 * parameter. This is not the recommended approach, and should be avoided.
063 * <p/>
064 * The {@link org.apache.camel.processor.aggregate.AggregateProcessor} will ensure that the exchange received from
065 * {@link OptimisticLockingAggregationRepository#get(org.apache.camel.CamelContext, String)} is passed as {@code oldExchange},
066 * and that the aggregated exchange received from the {@link org.apache.camel.processor.aggregate.AggregationStrategy}
067 * is passed as the {@code newExchange}.
068 *
069 * @param camelContext the current CamelContext
070 * @param key the correlation key
071 * @param oldExchange the old exchange that is expected to exist when replacing with the new exchange
072 * @param newExchange the new aggregated exchange, to replace old exchange
073 * @return the old exchange if any existed
074 * @throws OptimisticLockingException This should be thrown when the currently stored exchange differs from the supplied oldExchange.
075 */
076 Exchange add(CamelContext camelContext, String key, Exchange oldExchange, Exchange newExchange) throws OptimisticLockingException;
077
078 /**
079 * Removes the given Exchange when both the supplied key and Exchange are present in the repository. If the supplied Exchange
080 * does not match the Exchange actually stored against the key this method should throw an OptimisticLockingException
081 * to indicate that the value of the correlation key has changed from the expected value.
082 * <p/>
083 * @param camelContext the current CamelContext
084 * @param key the correlation key
085 * @param exchange the exchange to remove
086 * @throws OptimisticLockingException This should be thrown when the exchange has already been deleted, or otherwise modified.
087 */
088 void remove(CamelContext camelContext, String key, Exchange exchange) throws OptimisticLockingException;
089 }