Package org.axonframework.eventsourcing.eventstore

Class AbstractEventStore

java.lang.Object
org.axonframework.eventhandling.AbstractEventBus
org.axonframework.eventsourcing.eventstore.AbstractEventStore
All Implemented Interfaces:
DomainEventSequenceAware, EventBus, EventStore, MessageDispatchInterceptorSupport<EventMessage<?>>, StreamableMessageSource<TrackedEventMessage<?>>, SubscribableMessageSource<EventMessage<?>>
Direct Known Subclasses:
AxonServerEventStore, EmbeddedEventStore, EmbeddedEventStore
public abstract class AbstractEventStore extends AbstractEventBus implements EventStore
Abstract implementation of an EventStore that uses a EventStorageEngine to store and load events.
Since:
3.0
Author:
Rene de Waele

  • Constructor Details

  • Method Details

    • prepareCommit

      protected void prepareCommit(List<? extends EventMessage<?>> events)
      Description copied from class: AbstractEventBus
      Process given events while the Unit of Work root is preparing for commit. The default implementation signals the registered MessageMonitor that the given events are ingested and passes the events to each registered event processor.
      Overrides:
      prepareCommit in class AbstractEventBus
      Parameters:
      events - Events to be published by this Event Bus

    • readEvents

      public DomainEventStream readEvents(@Nonnull String aggregateIdentifier)
      Open an event stream containing all domain events belonging to the given aggregateIdentifier.

      The returned stream is finite, ending with the last known event of the aggregate. If the event store holds no events of the given aggregate an empty stream is returned.

      This implementation returns a DomainEventStream starting with the last stored snapshot of the aggregate followed by subsequent domain events.

      Specified by:
      readEvents in interface EventStore
      Parameters:
      aggregateIdentifier - the identifier of the aggregate whose events to fetch
      Returns:
      a stream of all currently stored events of the aggregate

    • handleSnapshotReadingError

      protected Optional<DomainEventMessage<?>> handleSnapshotReadingError(String aggregateIdentifier, Throwable e)
      Invoked when an error (Exception or LinkageError) occurs while attempting to read a snapshot event. This method can be overridden to change the default behavior, which is to log the exception (warn level) and ignore the snapshot.

      Overriding implementations may choose to return normally, or raise an exception. Exceptions raised from this method are propagated to the caller of the readEvents(String) or readEvents(String, long) methods.

      Returning an empty Optional will force the initialization of the aggregate to happen based on the entire event stream of that aggregate.

      Parameters:
      aggregateIdentifier - The identifier of the aggregate for which an snapshot failed to load
      e - The exception or error that occurred while loading or deserializing the snapshot
      Returns:
      An optional DomainEventMessage to use as the snapshot for this aggregate
      Throws:
      RuntimeException - any runtimeException to fail loading the

    • stagedDomainEventMessages

      protected Stream<? extends DomainEventMessage<?>> stagedDomainEventMessages(String aggregateIdentifier)
      Returns a Stream of all DomainEventMessages that have been staged for publication by an Aggregate with given aggregateIdentifier.
      Parameters:
      aggregateIdentifier - The identifier of the aggregate to get staged events for
      Returns:
      a Stream of DomainEventMessage of the identified aggregate

    • readEvents

      public DomainEventStream readEvents(@Nonnull String aggregateIdentifier, long firstSequenceNumber)
      Description copied from interface: EventStore
      Open an event stream containing all domain events belonging to the given aggregateIdentifier.

      The returned stream is finite, ending with the last known event of the aggregate. If the event store holds no events of the given aggregate an empty stream is returned.

      The default implementation invokes EventStore.readEvents(String) and then filters out events with a sequence number smaller than firstSequenceNumber.

      Specified by:
      readEvents in interface EventStore
      Parameters:
      aggregateIdentifier - the identifier of the aggregate whose events to fetch
      firstSequenceNumber - the expected sequence number of the first event in the returned stream
      Returns:
      a stream of all currently stored events of the aggregate

    • storeSnapshot

      public void storeSnapshot(@Nonnull DomainEventMessage<?> snapshot)
      Description copied from interface: EventStore
      Stores the given (temporary) snapshot event. This snapshot replaces the segment of the event stream identified by the snapshot's Aggregate Identifier up to (and including) the event with the snapshot's sequence number.

      These snapshots will only affect the DomainEventStream returned by the EventStore.readEvents(String) method. They do not change the events returned by StreamableMessageSource.openStream(TrackingToken) or those received by using SubscribableMessageSource.subscribe(java.util.function.Consumer).

      Note that snapshots are considered a temporary replacement for Events, and are used as performance optimization. Event Store implementations may choose to ignore or delete snapshots.

      Specified by:
      storeSnapshot in interface EventStore
      Parameters:
      snapshot - The snapshot to replace part of the DomainEventStream.

    • storageEngine

      protected EventStorageEngine storageEngine()
      Returns the EventStorageEngine used by the event store.
      Returns:
      The event storage engine used by this event store

    • lastSequenceNumberFor

      public Optional<Long> lastSequenceNumberFor(String aggregateIdentifier)
      Description copied from interface: DomainEventSequenceAware
      Returns the last known sequence number of an Event for the given aggregateIdentifier.

      It is preferred to retrieve the last known sequence number from the Domain Event Stream when sourcing an Aggregate from events. However, this method provides an alternative in cases no events have been read. For example when using state storage.

      Specified by:
      lastSequenceNumberFor in interface DomainEventSequenceAware
      Specified by:
      lastSequenceNumberFor in interface EventStore
      Parameters:
      aggregateIdentifier - the identifier of the aggregate to find the highest sequence for
      Returns:
      an optional containing the highest sequence number found, or an empty optional is no events are found for this aggregate

    • createTailToken

      public TrackingToken createTailToken()
      Description copied from interface: StreamableMessageSource
      Creates the token at the beginning of an event stream. The beginning of an event stream in this context means the token of very first event in the stream.

      The default behavior for this method is to return null, which always represents the tail position of a stream. However, implementations are encouraged to return an instance that explicitly represents the tail of the stream.

      Specified by:
      createTailToken in interface StreamableMessageSource<TrackedEventMessage<?>>
      Returns:
      the token at the beginning of an event stream

    • createHeadToken

      public TrackingToken createHeadToken()
      Description copied from interface: StreamableMessageSource
      Creates the token at the end of an event stream. The end of an event stream in this context means the token of very last event in the stream.
      Specified by:
      createHeadToken in interface StreamableMessageSource<TrackedEventMessage<?>>
      Returns:
      the token at the end of an event stream

    • createTokenAt

      public TrackingToken createTokenAt(Instant dateTime)
      Description copied from interface: StreamableMessageSource
      Creates a token that tracks all events after given dateTime. If there is an event exactly at the given dateTime, it will be tracked too.
      Specified by:
      createTokenAt in interface StreamableMessageSource<TrackedEventMessage<?>>
      Parameters:
      dateTime - The date and time for determining criteria how the tracking token should be created. A tracking token should point at very first event before this date and time.
      Returns:
      a tracking token at the given dateTime, if there aren't events matching this criteria null is returned