Package org.dspace.event

Interface Consumer

All Known Implementing Classes:

AuthorityConsumer, CheckerConsumer, DOIConsumer, EPersonConsumer, IIIFCacheEventConsumer, IndexEventConsumer, OrcidQueueConsumer, RDFConsumer, StatisticsLoggingConsumer, SubmissionConfigConsumer, TestConsumer, VersioningConsumer

public interface Consumer

Interface for content event consumers. Note that the consumer cannot tell if it is invoked synchronously or asynchronously; the consumer interface and sequence of calls is the same for both. Asynchronous consumers may see more consume() calls between the start and end of the event stream, if they are invoked asynchronously, once in a long time period, rather than synchronously after every Context.commit().

Method Summary

Modifier and Type	Method	Description
void	consume(Context ctx, Event event)	Consume an event.
void	end(Context ctx)	Signal that there are no more events queued in this event stream and event processing for the preceding consume calls should be finished up.
void	finish(Context ctx)	Finish - free any allocated resources.
void	initialize()	Allocate any resources required to operate.

Method Detail

initialize

void initialize()
         throws Exception

Allocate any resources required to operate. This may include initializing any pooled JMS resources. Called ONCE when created by the dispatcher pool. This should be used to set up expensive resources that will remain for the lifetime of the consumer.

Throws:

Exception - if error

consume

void consume(Context ctx,
             Event event)
      throws Exception

Consume an event. Events may be filtered by a dispatcher, hiding them from the consumer. This behavior is based on the dispatcher/consumer configuration. Should include logic to initialize any resources required for a batch of events.

This method must not commit the context. Committing causes re-dispatch of the event queue, which can result in infinite recursion leading to memory exhaustion as seen in {@link https://github.com/DSpace/DSpace/pull/8756}.

Parameters:

ctx - the current DSpace session

event - the content event

Throws:

Exception - if error

end

void end(Context ctx)
  throws Exception

Signal that there are no more events queued in this event stream and event processing for the preceding consume calls should be finished up.

Parameters:

ctx - the execution context object

Throws:

Exception - if error

finish

void finish(Context ctx)
     throws Exception

Finish - free any allocated resources. Called when consumer (via it's parent dispatcher) is going to be destroyed by the dispatcher pool.

Parameters:

ctx - the execution context object

Throws:

Exception - if error