Add something to easily handle the mapping of Enum in database

Hello.

I wonder if it would be possible to add something to easily handle mapping of Enum type in database ? A mapper which map an Enum Kotlin field into a VARCHAR database field.

Maybe adding a specific SqlType for the enums ?

What do you think about that ?

[vincentlauvlwj]

We can add a SqlType implementation to handle enums:

fun <E : Any, C : Enum<C>> BaseTable<E>.enum(name: String, typeRef: TypeReference<C>): BaseTable<E>.ColumnRegistration<C> {
    return registerColumn(name, EnumSqlType(typeRef.referencedType as Class<C>))
}

class EnumSqlType<C : Enum<C>>(val enumClass: Class<C>) : SqlType<C>(Types.VARCHAR, "varchar") {
    private val valueOf = enumClass.getDeclaredMethod("valueOf", String::class.java)

    override fun doSetParameter(ps: PreparedStatement, index: Int, parameter: C) {
        ps.setString(index, parameter.name)
    }

    override fun doGetResult(rs: ResultSet, index: Int): C? {
        return rs.getString(index)?.takeIf { it.isNotBlank() }?.let { enumClass.cast(valueOf(null, it)) }
    }
}

Usage:

object Employees : Table<Nothing>("t_employee") {
    // ...
    val sex by enum("sex", typeRef<Sex>())
}

[vincentlauvlwj]

Ktorm 2.7 is released.