Lagom Persistent Entity's command or event class changed

[Roman]

In case of changing entity's class there is an ability to override entityTypeName. But in case of changing command's or event's class, that don't have a such propery cause no extending PersistentEntity class. How to refactor code in such case?

For example, we have the following entity class:

public class UserEntity extends PersistentEntity<UserCommand, UserEvent, User> {
...
}

And now we'd like to move UserCommand and UserEvent classes to another package. When do that the error is traced:

[ERROR] from com.lightbend.lagom.internal.javadsl.persistence.PersistentEntityActor in ecs-user-service-akka.actor.default-dispatcher-18 - Persistence failure when replaying events for persistenceId [UserEntitybda2d45f-0b0c-3184-8342-a441eab3b19a]. Last known sequence number [0]
java.io.NotSerializableException: Cannot find manifest class [com.idbs.ecs.ur.api.UserAddedEvent] for serializer [com.lightbend.lagom.internal.jackson.JacksonJsonSerializer].
...

Is it possible to do properly in Lagom world?

[James Roper]

You need to define migrations when you change the class name or schema of events or state:

https://www.lagomframework.com/documentation/1.3.x/java/Serialization.html#Schema-Evolution

The same migrations will actually work for commands too (anything that's implementing Jsonable, since the migration support is handled in the Jackson serializer).

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James Roper
Software Engineer

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[Roman]

James,

Thanks for your replay, will get in mind! 

For now, we decided just to revert the changes.