Add the ability to override how enums are mapped to the database.

Use case

I would like to able to map enums in Kotlin to integers in the database. The pre-existing databases that I am developing against (in SQL Server) have all the enum-like columns stored as integers often with a backing constraint table.

Describe the solution you’d like

I would like to be able to provide a custom DataType converter to map the enums but it does not work. The komapper-processor is currently hard-coded to prioitise mapping enums to strings.

https://github.com/komapper/komapper/blob/fdf89c272c272fa5b56ee8e18e1afb326b5ae4ee/komapper-processor/src/main/kotlin/org/komapper/processor/EntityFactory.kt#L62

Versions

• Komapper: 1.0.0-RC1
• Kotlin: 1.6.21
• JVM: JDK 14.0.1
• JDBC Driver or R2DBC Driver: com.microsoft.sqlserver:mssql-jdbc:10.2.0.jre11
• Database: SQL Server 2014
• OS: Windows 10

[donard-commedagh]

That’s a good idea, I’ve only just read up on value classes in the last week and haven’t used them anywhere yet. As a temporary fix, I can live without the exhaustive when(enum) and enum.values()

Thank you for the excellent work developing Komapper.

[nakamura-to]

By the way, you can use value class instead of enum class. For example, the following code works with Komapper 1.0.0-RC1:

@JvmInline
value class Color(val value: Int) {
    companion object {
        val BLUE = Color(0)
        val RED = Color(1)
        val YELLOW = Color(2)
    }
}

@KomapperEntity
data class Pencil(
    @KomapperId
    val id: Int,
    val color: Color
)