Session Serializers

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    Serializers

    You can specify a custom serializer with:

    application.install(Sessions) {
    cookie<MySession>("SESSION") {
        serializer = MyCustomSerializer()
    }
}

    If you do not specify any serializer, it will use one with an internal optimized format.

    SessionSerializerReflection

    This is the default serializer, when no serializer is specified:

    cookie<MySession>("SESSION") {
    serializer = autoSerializerOf()
}

    GsonSessionSerializer

    Using JSON instead of the default serializer. Note that the payload will be bigger:

    cookie<MySession>("SESSION") {
    serializer = gsonSessionSerializer()
}

    This serializes requires the artifact io.ktor:ktor-gson:$ktor_version.

    Custom serializers

    The Sessions API provides a SessionSerializer interface, that looks like this:

    interface SessionSerializer {
    fun serialize(session: Any): String
    fun deserialize(text: String): Any
}

    This interface is for a generic serializer, and you can install it like this:

    cookie<MySession>("NAME") {
    serializer = MyCustomSerializer()
}

    So for example you can create a JSON session serializer using Gson:

    class GsonSessionSerializer(
    val type: java.lang.reflect.Type, val gson: Gson = Gson(), configure: Gson.() -> Unit = {}
) : SessionSerializer {
    init {
        configure(gson)
    }

    override fun serialize(session: Any): String = gson.toJson(session)
    override fun deserialize(text: String): Any = gson.fromJson(text, type)
}

    And configuring it:

    cookie<MySession>("NAME") {
    serializer = GsonSessionSerializer(MySession::class.java)
}