Package akka.javasdk.annotations

Annotation Interface ProtoEventTypes

@Target(TYPE) @Retention(RUNTIME) @Documented public @interface ProtoEventTypes
Declares the concrete protobuf message classes used as events.

This annotation is only needed when using protobuf messages (GeneratedMessageV3 subclasses) as events. When using Java sealed interfaces for events, the event types are automatically discovered from the permitted subclasses.

Can be applied to:

  • Event Sourced Entities — declares the allowed event types. If the entity tries to persist an event type not listed, the operation fails. The applyEvent handler accepts GeneratedMessageV3 and uses pattern matching to handle each type.
  • Consumers — declares the protobuf event types the consumer handles. When a handler method accepts GeneratedMessageV3, the annotation tells the SDK which concrete types to of messages that are expected. If another type of message arrives to the consumer it will fail processing it. If the annotation is not present, the types are auto-resolved from the source entity's @ProtoEventTypes annotation if it is a local event sourced entity (using Consume.FromEventSourcedEntity.)
  • View TableUpdaters — same as consumers: declares the protobuf event types the updater handles. If omitted, types are auto-resolved from the source entity.

Example usage on an Event Sourced Entity: 


 @ComponentId("my-entity")
 @ProtoEventTypes({CustomerCreated.class, CustomerNameChanged.class})
 public class MyEntity extends EventSourcedEntity<MyState, GeneratedMessageV3> {
   // ...
 }

Example usage on a Consumer (explicit types): 


 @ComponentId("my-consumer")
 @Consume.FromEventSourcedEntity(MyEntity.class)
 @ProtoEventTypes({CustomerCreated.class, CustomerNameChanged.class})
 public class MyConsumer extends Consumer {
   public Effect onEvent(GeneratedMessageV3 event) { ... }
 }

When consuming from an entity that already has @ProtoEventTypes, the annotation on the consumer or view can be omitted and the types will be resolved from the source entity automatically.

  • Required Element Summary

    Required Elements
    Modifier and Type
    Required Element
    Description
    Class<? extends com.google.protobuf.GeneratedMessageV3>[]
    value
    The protobuf message classes used as event types.

  • Element Details

    • value

      Class<? extends com.google.protobuf.GeneratedMessageV3>[] value
      The protobuf message classes used as event types.
      Returns:
      array of protobuf message classes representing the event types