Package org.dspace.event

Interface Consumer

All Known Implementing Classes:
AuthorityConsumer, CheckerConsumer, DOIConsumer, EPersonConsumer, IIIFCacheEventConsumer, IndexEventConsumer, LDNMessageConsumer, OrcidQueueConsumer, QAEventsDeleteCascadeConsumer, 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 Details

    • 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