akka.persistence.journal

Interface ReadEventAdapter

All Known Subinterfaces:

EventAdapter

All Known Implementing Classes:

EventAdapters.CombinedReadEventAdapter, IdentityEventAdapter$, NoopReadEventAdapter, NoopWriteEventAdapter

public interface ReadEventAdapter

Facility to convert from and to specialised data models, as may be required by specialized persistence Journals.

Typical use cases include (but are not limited to):

• extracting events from "envelopes"
• manually converting to the Journals storage format, such as JSON, BSON or any specialised binary format
• adapting incoming events from a "data model" to the "domain model"

Method Summary

Modifier and Type	Method and Description
EventSeq	fromJournal(java.lang.Object event, java.lang.String manifest) Convert a event from its journal model to the applications domain model.

Method Detail

fromJournal

EventSeq fromJournal(java.lang.Object event,
                     java.lang.String manifest)

Convert a event from its journal model to the applications domain model.

One event may be adapter into multiple (or none) events which should be delivered to the PersistentActor. Use the specialised EventSeq.single(java.lang.Object) method to emit exactly one event, or EventSeq.empty() in case the adapter is not handling this event. Multiple EventAdapter instances are applied in order as defined in configuration and their emitted event seqs are concatenated and delivered in order to the PersistentActor.

Parameters:

event - event to be adapted before delivering to the PersistentActor

manifest - optionally provided manifest (type hint) in case the Adapter has stored one for this event, "" if none

Returns:

sequence containing the adapted events (possibly zero) which will be delivered to the PersistentActor