[FLINK-3039] Trigger KeyValueState cannot be Scala Int

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 0.10.0
• Fix Version/s: 1.0.0
• Component/s: API / DataStream, Runtime / State Backends
• Assignee: Unassigned
• Reporter: Fabian Hueske
• Created: 18/Nov/15 16:39
• Updated: 30/Jan/17 14:48
• Resolved: 30/Jan/17 14:48

Description

It is not possible to use a Scala Int as a KeyValueState in a Trigger function because TriggerContext.getKeyValueState requires that the state is Serializable.

override def onElement(e: (Int, Short), t: Long, w: TimeWindow, ctx: TriggerContext): TriggerResult = {
      val cnt = ctx.getKeyValueState[Int]("cnt", 0)
      ...
}

will fail with

Error:(116, 44) type arguments [Int] do not conform to method getKeyValueState's type parameter bounds [S <: java.io.Serializable]
      val cnt = ctx.getKeyValueState[Int]("cnt", 0)
                                           ^

If I change Int to Integer, the code compiles.