Serializable and serialVersionUid in Kotlin

To create the serialVersionUID for a class in Kotlin you have a few options all involving adding a member to the companion object of the class.

The most concise bytecode comes from a private const val which will become a private static variable on the containing class, in this case MySpecialCase:

class MySpecialCase : Serializable {
    companion object {
        private const val serialVersionUID: Long = 123
    }
}

You can also use these forms, each with a side effect of having getter/setter methods which are not necessary for serialization…

class MySpecialCase : Serializable {
    companion object {
        private val serialVersionUID: Long = 123
    }
}

This creates the static field but also creates a getter as well getSerialVersionUID on the companion object which is unnecessary.

class MySpecialCase : Serializable {
    companion object {
        @JvmStatic private val serialVersionUID: Long = 123
    }
}

This creates the static field but also creates a static getter as well getSerialVersionUID on the containing class MySpecialCase which is unnecessary.

But all work as a method of adding the serialVersionUID to a Serializable class.