core/camel-api/src/main/java/org/apache/camel/AggregationStrategy.java - camel - Git at Google

 /*
  * 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.
  */
 package org.apache.camel;

 import org.slf4j.LoggerFactory;

 /**
  * A strategy for aggregating two exchanges together into a single exchange.
  * <p/>
  * On the first invocation of the {@link #aggregate(org.apache.camel.Exchange, org.apache.camel.Exchange) aggregate}
  * method the <tt>oldExchange</tt> parameter is <tt>null</tt>. The reason is that we have not aggregated anything yet.
  * So its only the <tt>newExchange</tt> that has a value. Usually you just return the <tt>newExchange</tt> in this
  * situation. But you still have the power to decide what to do, for example you can do some alternation on the exchange
  * or remove some headers. And a more common use case is for instance to count some values from the body payload. That
  * could be to sum up a total amount etc.
  * <p/>
  * Note that <tt>oldExchange</tt> may be <tt>null</tt> more than once when this strategy is throwing a {@link java.lang.RuntimeException}
  * and <tt>parallelProcessing</tt> is used. You can work around this behavior using the <tt>stopOnAggregateException</tt> option.
  * <p/>
  * It is possible that <tt>newExchange</tt> is <tt>null</tt> which could happen if there was no data possible
  * to acquire. Such as when using a <tt>PollEnricher</tt> to poll from a JMS queue which
  * is empty and a timeout was set.
  * <p/>
  * Important: In the aggregate method, do not create a new exchange instance to return,
  * instead return either the old or new exchange from the input parameters; favor returning the old exchange whenever possible.
  * <p/>
  * Possible implementations include performing some kind of combining or delta processing, such as adding line items
  * together into an invoice or just using the newest exchange and removing old exchanges such as for state tracking or
  * market data prices; where old values are of little use.
  * <p/>
  * If an implementation also implements {@link org.apache.camel.Service} then any <a href="http://camel.apache.org/eip">EIP</a>
  * that allowing configuring a {@link AggregationStrategy} will invoke the {@link org.apache.camel.Service#start()}
  * and {@link org.apache.camel.Service#stop()} to control the lifecycle aligned with the EIP itself.
  * <p/>
  * If an implementation also implements {@link org.apache.camel.CamelContextAware} then any <a href="http://camel.apache.org/eip">EIP</a>
  * that allowing configuring a {@link AggregationStrategy} will inject the {@link org.apache.camel.CamelContext} prior
  * to using the aggregation strategy.
  */
 public interface AggregationStrategy {

     /**
      * Aggregates an old and new exchange together to create a single combined exchange
      * <p/>
      * Important: In the aggregate method, do not create a new exchange instance to return,
      * instead return either the old or new exchange from the input parameters; favor returning the old exchange whenever possible.
      *
      * @param oldExchange the oldest exchange (is <tt>null</tt> on first aggregation as we only have the new exchange)
      * @param newExchange the newest exchange (can be <tt>null</tt> if there was no data possible to acquire)
      * @return a combined composite of the two exchanges, return either the old or new exchange from the input parameters;
      * favor returning the old exchange whenever possible)
      */
     Exchange aggregate(Exchange oldExchange, Exchange newExchange);

     /**
      * Aggregates an old and new exchange together to create a single combined exchange.
      * <p/>
      * Important: In the aggregate method, do not create a new exchange instance to return,
      * instead return either the old or new exchange from the input parameters; favor returning the old exchange whenever possible.
      * <p/>
      * Important: Only Multicast and Recipient List EIP supports this method with access to the input exchange. All other EIPs
      * does not and uses the {@link #aggregate(Exchange, Exchange)} method instead.
      *
      * @param oldExchange    the oldest exchange (is <tt>null</tt> on first aggregation as we only have the new exchange)
      * @param newExchange    the newest exchange (can be <tt>null</tt> if there was no data possible to acquire)
      * @param inputExchange  the input exchange (input to the EIP)
      * @return a combined composite of the two exchanges, return either the old or new exchange from the input parameters;
      * favor returning the old exchange whenever possible)
      */
     default Exchange aggregate(Exchange oldExchange, Exchange newExchange, Exchange inputExchange) {
         return aggregate(oldExchange, newExchange);
     }

     /**
      * Indicates if this aggregation strategy uses pre-completion mode.
      * @return <tt>true</tt> if this strategy uses pre-completion mode, or <tt>false</tt> otherwise.
      */
     default boolean canPreComplete() {
         return false;
     }

     /**
      * Determines if the aggregation should complete the current group, and start a new group, or the aggregation
      * should continue using the current group. This callback will only be called if {@link #canPreComplete()}
      * returns <tt>true</tt>.
      *
      * @param oldExchange the oldest exchange (is <tt>null</tt> on first aggregation as we only have the new exchange)
      * @param newExchange the newest exchange (can be <tt>null</tt> if there was no data possible to acquire)
      * @return <tt>true</tt> to complete current group and start a new group, or <tt>false</tt> to keep using current
      */
     default boolean preComplete(Exchange oldExchange, Exchange newExchange) {
         return false;
     }

     /**
      * The aggregated {@link Exchange} has completed
      *
      * <b>Important: </b> This method must <b>not</b> throw any exceptions.
      *
      * @param exchange  the current aggregated exchange, or the original {@link org.apache.camel.Exchange} if no aggregation
      *                  has been done before the completion occurred
      */
     default void onCompletion(Exchange exchange) {
     }

     /**
      * A timeout occurred.
      * <p/>
      * <b>Important: </b> This method must <b>not</b> throw any exceptions.
      *
      * @param exchange  the current aggregated exchange, or the original {@link Exchange} if no aggregation
      *                  has been done before the timeout occurred
      * @param index     the index, may be <tt>-1</tt> if not possible to determine the index
      * @param total     the total, may be <tt>-1</tt> if not possible to determine the total
      * @param timeout   the timeout value in millis, may be <tt>-1</tt> if not possible to determine the timeout
      */
     default void timeout(Exchange exchange, int index, int total, long timeout) {
         // log a WARN we timed out since it will not be aggregated and the Exchange will be lost
         LoggerFactory.getLogger(getClass()).warn("Parallel processing timed out after {} millis for number {}. This task will be cancelled and will not be aggregated.", timeout, index);
     }

     /**
      * Callback when the aggregated {@link Exchange} fails to add
      * in the {@link org.apache.camel.spi.OptimisticLockingAggregationRepository} because of
      * an {@link org.apache.camel.spi.OptimisticLockingAggregationRepository.OptimisticLockingException}.
      * <p/>
      * Please note that when aggregating {@link Exchange}'s to be careful not to modify and return the {@code oldExchange}
      * from the {@link AggregationStrategy#aggregate(org.apache.camel.Exchange, org.apache.camel.Exchange)} method.
      * If you are using the default MemoryAggregationRepository this will mean you have modified the value of an object
      * already referenced/stored by the MemoryAggregationRepository. This makes it impossible for optimistic locking
      * to work correctly with the MemoryAggregationRepository.
      * <p/>
      * You should instead return either the new {@code newExchange} or a completely new instance of {@link Exchange}. This
      * is due to the nature of how the underlying {@link java.util.concurrent.ConcurrentHashMap} performs CAS operations
      * on the value identity.
      *
      * @see java.util.concurrent.ConcurrentHashMap
      */
     default void onOptimisticLockFailure(Exchange oldExchange, Exchange newExchange) {
         LoggerFactory.getLogger(getClass()).trace("onOptimisticLockFailure with AggregationStrategy: {}, oldExchange: {}, newExchange: {}", this, oldExchange, newExchange);
     }

 }
	/*
	* 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.
	*/
	package org.apache.camel;

	import org.slf4j.LoggerFactory;

	/**
	* A strategy for aggregating two exchanges together into a single exchange.
	* <p/>
	* On the first invocation of the {@link #aggregate(org.apache.camel.Exchange, org.apache.camel.Exchange) aggregate}
	* method the <tt>oldExchange</tt> parameter is <tt>null</tt>. The reason is that we have not aggregated anything yet.
	* So its only the <tt>newExchange</tt> that has a value. Usually you just return the <tt>newExchange</tt> in this
	* situation. But you still have the power to decide what to do, for example you can do some alternation on the exchange
	* or remove some headers. And a more common use case is for instance to count some values from the body payload. That
	* could be to sum up a total amount etc.
	* <p/>
	* Note that <tt>oldExchange</tt> may be <tt>null</tt> more than once when this strategy is throwing a {@link java.lang.RuntimeException}
	* and <tt>parallelProcessing</tt> is used. You can work around this behavior using the <tt>stopOnAggregateException</tt> option.
	* <p/>
	* It is possible that <tt>newExchange</tt> is <tt>null</tt> which could happen if there was no data possible
	* to acquire. Such as when using a <tt>PollEnricher</tt> to poll from a JMS queue which
	* is empty and a timeout was set.
	* <p/>
	* Important: In the aggregate method, do not create a new exchange instance to return,
	* instead return either the old or new exchange from the input parameters; favor returning the old exchange whenever possible.
	* <p/>
	* Possible implementations include performing some kind of combining or delta processing, such as adding line items
	* together into an invoice or just using the newest exchange and removing old exchanges such as for state tracking or
	* market data prices; where old values are of little use.
	* <p/>
	* If an implementation also implements {@link org.apache.camel.Service} then any <a href="http://camel.apache.org/eip">EIP</a>
	* that allowing configuring a {@link AggregationStrategy} will invoke the {@link org.apache.camel.Service#start()}
	* and {@link org.apache.camel.Service#stop()} to control the lifecycle aligned with the EIP itself.
	* <p/>
	* If an implementation also implements {@link org.apache.camel.CamelContextAware} then any <a href="http://camel.apache.org/eip">EIP</a>
	* that allowing configuring a {@link AggregationStrategy} will inject the {@link org.apache.camel.CamelContext} prior
	* to using the aggregation strategy.
	*/
	public interface AggregationStrategy {

	/**
	* Aggregates an old and new exchange together to create a single combined exchange
	* <p/>
	* Important: In the aggregate method, do not create a new exchange instance to return,
	* instead return either the old or new exchange from the input parameters; favor returning the old exchange whenever possible.
	*
	* @param oldExchange the oldest exchange (is <tt>null</tt> on first aggregation as we only have the new exchange)
	* @param newExchange the newest exchange (can be <tt>null</tt> if there was no data possible to acquire)
	* @return a combined composite of the two exchanges, return either the old or new exchange from the input parameters;
	* favor returning the old exchange whenever possible)
	*/
	Exchange aggregate(Exchange oldExchange, Exchange newExchange);

	/**
	* Aggregates an old and new exchange together to create a single combined exchange.
	* <p/>
	* Important: In the aggregate method, do not create a new exchange instance to return,
	* instead return either the old or new exchange from the input parameters; favor returning the old exchange whenever possible.
	* <p/>
	* Important: Only Multicast and Recipient List EIP supports this method with access to the input exchange. All other EIPs
	* does not and uses the {@link #aggregate(Exchange, Exchange)} method instead.
	*
	* @param oldExchange the oldest exchange (is <tt>null</tt> on first aggregation as we only have the new exchange)
	* @param newExchange the newest exchange (can be <tt>null</tt> if there was no data possible to acquire)
	* @param inputExchange the input exchange (input to the EIP)
	* @return a combined composite of the two exchanges, return either the old or new exchange from the input parameters;
	* favor returning the old exchange whenever possible)
	*/
	default Exchange aggregate(Exchange oldExchange, Exchange newExchange, Exchange inputExchange) {
	return aggregate(oldExchange, newExchange);
	}

	/**
	* Indicates if this aggregation strategy uses pre-completion mode.
	* @return <tt>true</tt> if this strategy uses pre-completion mode, or <tt>false</tt> otherwise.
	*/
	default boolean canPreComplete() {
	return false;
	}

	/**
	* Determines if the aggregation should complete the current group, and start a new group, or the aggregation
	* should continue using the current group. This callback will only be called if {@link #canPreComplete()}
	* returns <tt>true</tt>.
	*
	* @param oldExchange the oldest exchange (is <tt>null</tt> on first aggregation as we only have the new exchange)
	* @param newExchange the newest exchange (can be <tt>null</tt> if there was no data possible to acquire)
	* @return <tt>true</tt> to complete current group and start a new group, or <tt>false</tt> to keep using current
	*/
	default boolean preComplete(Exchange oldExchange, Exchange newExchange) {
	return false;
	}

	/**
	* The aggregated {@link Exchange} has completed
	*
	* <b>Important: </b> This method must <b>not</b> throw any exceptions.
	*
	* @param exchange the current aggregated exchange, or the original {@link org.apache.camel.Exchange} if no aggregation
	* has been done before the completion occurred
	*/
	default void onCompletion(Exchange exchange) {
	}

	/**
	* A timeout occurred.
	* <p/>
	* <b>Important: </b> This method must <b>not</b> throw any exceptions.
	*
	* @param exchange the current aggregated exchange, or the original {@link Exchange} if no aggregation
	* has been done before the timeout occurred
	* @param index the index, may be <tt>-1</tt> if not possible to determine the index
	* @param total the total, may be <tt>-1</tt> if not possible to determine the total
	* @param timeout the timeout value in millis, may be <tt>-1</tt> if not possible to determine the timeout
	*/
	default void timeout(Exchange exchange, int index, int total, long timeout) {
	// log a WARN we timed out since it will not be aggregated and the Exchange will be lost
	LoggerFactory.getLogger(getClass()).warn("Parallel processing timed out after {} millis for number {}. This task will be cancelled and will not be aggregated.", timeout, index);
	}

	/**
	* Callback when the aggregated {@link Exchange} fails to add
	* in the {@link org.apache.camel.spi.OptimisticLockingAggregationRepository} because of
	* an {@link org.apache.camel.spi.OptimisticLockingAggregationRepository.OptimisticLockingException}.
	* <p/>
	* Please note that when aggregating {@link Exchange}'s to be careful not to modify and return the {@code oldExchange}
	* from the {@link AggregationStrategy#aggregate(org.apache.camel.Exchange, org.apache.camel.Exchange)} method.
	* If you are using the default MemoryAggregationRepository this will mean you have modified the value of an object
	* already referenced/stored by the MemoryAggregationRepository. This makes it impossible for optimistic locking
	* to work correctly with the MemoryAggregationRepository.
	* <p/>
	* You should instead return either the new {@code newExchange} or a completely new instance of {@link Exchange}. This
	* is due to the nature of how the underlying {@link java.util.concurrent.ConcurrentHashMap} performs CAS operations
	* on the value identity.
	*
	* @see java.util.concurrent.ConcurrentHashMap
	*/
	default void onOptimisticLockFailure(Exchange oldExchange, Exchange newExchange) {
	LoggerFactory.getLogger(getClass()).trace("onOptimisticLockFailure with AggregationStrategy: {}, oldExchange: {}, newExchange: {}", this, oldExchange, newExchange);
	}

	}