How to implement org.hibernate.Session in Scala

Question

The "Session" interface has two methods that, in Scala due to type erasure, are reduced to having the same signature:

public ProcedureCall createStoredProcedureCall(String procedureName, Class... resultClasses)

public ProcedureCall createStoredProcedureCall(String procedureName, String... resultSetMappings)

Trying to implement them gives the error:

error: double definition: method createStoredProcedureCall:(procedureName: String, resultSetMappings: String*)org.hibernate.procedure.ProcedureCall and method createStoredProcedureCall:(procedureName: String, resultClasses: Class[_])org.hibernate.procedure.ProcedureCall at line 199 have same type after erasure: (procedureName: String, resultSetMappings: Seq)org.hibernate.procedure.ProcedureCall override def createStoredProcedureCall(procedureName: String, resultSetMappings: String): ProcedureCall = null ^

So how would I go about implementing this interface in a way that will both compile and work?

Answer 1

As serejja pointed out, you can write a shim in Java to do the translation for you:

Java:

package jibernate;

import org.hibernate.procedure.ProcedureCall;
import org.hibernate.SharedSessionContract;

public abstract class Yava implements SharedSessionContract {

  public ProcedureCall createStoredProcedureCallC(String n, Class... xs) {
    return createStoredProcedureCall(n, xs);
  }

  public ProcedureCall createStoredProcedureCallS(String n, String... xs) {
    return createStoredProcedureCall(n, xs);
  }

}

If you're using sbt, this can live in src/main/java/jibernate/Yava.java

Scala:

package whybernate

trait Mehssion extends jibernate.Yava {

  import org.hibernate.procedure.ProcedureCall

  def createStoredProcedureCall(n: String, h: Class[_], t: Class[_]*) =
    createStoredProcedureCallC(n, (h +: t):_*)

  def createStoredProcedureCall(n: String, h: String, t: String*) =
    createStoredProcedureCallS(n, (h +: t):_*)

}

You can call these functions in the same way, taking advantage of the fact that you're guaranteed to have at least one of the needed varargs.