Package org.apache.camel.spi

Interface OptimisticLockingAggregationRepository

All Superinterfaces:

AggregationRepository

public interface OptimisticLockingAggregationRepository
extends AggregationRepository

A specialized AggregationRepository which also supports optimistic locking. If the underlying implementation cannot perform optimistic locking, it should not implement this interface.

See Also:

org.apache.camel.processor.aggregate.MemoryAggregationRepository

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	OptimisticLockingAggregationRepository.OptimisticLockingException	Exception used by an AggregationRepository to indicate that an optimistic update error has occurred and that the operation should be retried by the caller.

Method Summary

Modifier and Type	Method	Description
Exchange	add(CamelContext camelContext, String key, Exchange oldExchange, Exchange newExchange)	Add the given Exchange under the correlation key.
void	remove(CamelContext camelContext, String key, Exchange exchange)	Removes the given Exchange when both the supplied key and Exchange are present in the repository.

Methods inherited from interface org.apache.camel.spi.AggregationRepository

add, confirm, get, getKeys

Method Detail

add

Exchange add(CamelContext camelContext,
             String key,
             Exchange oldExchange,
             Exchange newExchange)
      throws OptimisticLockingAggregationRepository.OptimisticLockingException

Add the given Exchange under the correlation key.

Will perform optimistic locking to replace expected existing exchange with the new supplied exchange.

If the oldExchange is null the underlying implementation is to assume this is the very first Exchange for the supplied correlation key. When the implementation comes to store to the Exchange if there is already an existing Exchange present for this correlation key the implementation should throw an OptimisticLockingException.

If the oldExchange is not null the underlying implementation should use it to compare with the existing exchange when doing an atomic compare-and-set/swap operation.

The implementation may achieve this by storing a version identifier in the Exchange as a parameter. Set before returning from AggregationRepository.get(org.apache.camel.CamelContext, String)} and retrieved from the exchange when passed to AggregationRepository.add(org.apache.camel.CamelContext, String, org.apache.camel.Exchange).

Note: The org.apache.camel.processor.aggregate.MemoryAggregationRepository is an exception to this recommendation. It uses the oldExchange's Object identify to perform it's compare-and-set/swap operation, instead of a version parameter. This is not the recommended approach, and should be avoided.

The org.apache.camel.processor.aggregate.AggregateProcessor will ensure that the exchange received from AggregationRepository.get(org.apache.camel.CamelContext, String) is passed as oldExchange, and that the aggregated exchange received from the org.apache.camel.processor.aggregate.AggregationStrategy is passed as the newExchange.

Parameters:

camelContext - the current CamelContext

key - the correlation key

oldExchange - the old exchange that is expected to exist when replacing with the new exchange

newExchange - the new aggregated exchange, to replace old exchange

Returns:

the old exchange if any existed

Throws:

OptimisticLockingAggregationRepository.OptimisticLockingException - This should be thrown when the currently stored exchange differs from the supplied oldExchange.

remove

void remove(CamelContext camelContext,
            String key,
            Exchange exchange)
     throws OptimisticLockingAggregationRepository.OptimisticLockingException

Removes the given Exchange when both the supplied key and Exchange are present in the repository. If the supplied Exchange does not match the Exchange actually stored against the key this method should throw an OptimisticLockingException to indicate that the value of the correlation key has changed from the expected value.

Specified by:

remove in interface AggregationRepository

Parameters:

camelContext - the current CamelContext

key - the correlation key

exchange - the exchange to remove

Throws:

OptimisticLockingAggregationRepository.OptimisticLockingException - This should be thrown when the exchange has already been deleted, or otherwise modified.