akka/akka-core

Persistence with Jackson trying to cast all Map keys to String

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#28,566 opened on Feb 4, 2020

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 (6 comments) (2 reactions) (0 assignees)Scala (3,547 forks)batch import
1 - triagedhelp wantedt:docst:serialization

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Description

scalaVersion "2.13.1" akkaVersion = "2.6.1"

akka {
  actor {
    serializers {
      jackson-json = "akka.serialization.jackson.JacksonJsonSerializer"
      jackson-cbor = "akka.serialization.jackson.JacksonCborSerializer"
    }
    serialization-bindings {
      "xxx.CborSerializable" = jackson-cbor
    }
  }
}

trait CborSerializable

final case class State(data:Map[Long,List[String]]) extends CborSerializable

// persist something with typed persistent actor.  eg. 42 -> List() 
// after snapshot recovery 

state.data.get(42) // should be Some, but it is None

state.data.find(_._1 == 42) // throws ex

Exception is

class java.lang.String cannot be cast to class java.lang.Long (java.lang.String and java.lang.Long are in module java.base of loader 'bootstrap') java.lang.ClassCastException: class java.lang.String cannot be cast to class java.lang.Long (java.lang.String and java.lang.Long are in module java.base of loader 'bootstrap')

Contributor guide

Research direction
Investigate how Jackson serializes Map keys in the Akka serialization context. The issue indicates that Long keys are being deserialized as Strings, causing ClassCastException. Check if a type annotation or custom key serializer is missing for the Map key type.
Tech stack
scala
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
ScalaAkkaJackson
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60