t

akka.persistence.journal

EventAdapter

trait EventAdapter extends WriteEventAdapter with ReadEventAdapter

An EventAdapter is both a WriteEventAdapter and a 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):

  • adding metadata, a.k.a. "tagging" - by wrapping objects into tagged counterparts
  • manually converting to the Journals storage format, such as JSON, BSON or any specialised binary format
  • adapting incoming events in any way before persisting them by the journal
Source
EventAdapter.scala
Linear Supertypes
ReadEventAdapter, WriteEventAdapter, AnyRef, Any
Known Subclasses
IdentityEventAdapter
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Inherited
  1. EventAdapter
  2. ReadEventAdapter
  3. WriteEventAdapter
  4. AnyRef
  5. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
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Abstract Value Members

  1. abstract def fromJournal(event: Any, manifest: String): EventSeq

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

    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 akka.persistence.PersistentActor. Use the specialised akka.persistence.journal.EventSeq#single method to emit exactly one event, or akka.persistence.journal.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.

    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

    Definition Classes
    ReadEventAdapter
  2. abstract def manifest(event: Any): String

    Return the manifest (type hint) that will be provided in the fromJournal method.

    Return the manifest (type hint) that will be provided in the fromJournal method. Use "" if manifest is not needed.

    Definition Classes
    WriteEventAdapter
  3. abstract def toJournal(event: Any): Any

    Convert domain event to journal event type.

    Convert domain event to journal event type.

    Some journal may require a specific type to be returned to them, for example if a primary key has to be associated with each event then a journal may require adapters to return com.example.myjournal.EventWithPrimaryKey(event, key).

    The toJournal adaptation must be an 1-to-1 transformation. It is not allowed to drop incoming events during the toJournal adaptation.

    event

    the application-side domain event to be adapted to the journal model

    returns

    the adapted event object, possibly the same object if no adaptation was performed

    Definition Classes
    WriteEventAdapter