abstract class Handler[Envelope] extends HandlerLifecycle

Implement this interface for the Envelope handler in the Projection. Some projections may have more specific handler types.

It can be stateful, with variables and mutable data structures. It is invoked by the Projection machinery one envelope at a time and visibility guarantees between the invocations are handled automatically, i.e. no volatile or other concurrency primitives are needed for managing the state.

Supported error handling strategies for when processing an Envelope fails can be defined in configuration or using the withRecoveryStrategy method of a Projection implementation.

Source
Handler.scala
Linear Supertypes
HandlerLifecycle, AnyRef, Any
Known Subclasses
ActorHandler, StatefulHandler
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Inherited
  1. Handler
  2. HandlerLifecycle
  3. AnyRef
  4. Any
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Visibility
  1. Public
  2. Protected

Instance Constructors

  1. new Handler()

Abstract Value Members

  1. abstract def process(envelope: Envelope): CompletionStage[Done]

    The process method is invoked for each Envelope.

    The process method is invoked for each Envelope. One envelope is processed at a time. The returned CompletionStage is to be completed when the processing of the envelope has finished. It will not be invoked with the next envelope until after the returned CompletionStage has been completed.

    Annotations
    @throws(classOf[Exception])

Concrete Value Members

  1. def start(): CompletionStage[Done]

    Invoked when the projection is starting, before first envelope is processed.

    Invoked when the projection is starting, before first envelope is processed. Can be overridden to implement initialization. It is also called when the Projection is restarted after a failure.

    Definition Classes
    Handler → HandlerLifecycle
  2. def stop(): CompletionStage[Done]

    Invoked when the projection has been stopped.

    Invoked when the projection has been stopped. Can be overridden to implement resource cleanup. It is also called when the Projection is restarted after a failure.

    Definition Classes
    Handler → HandlerLifecycle