When using Kotlin in an Enterprise Environment ™, ...

# announcements

[Gyuhyeon]

When using Kotlin in an Enterprise Environment ™, I make a model for MyBatis like so:

class UserModel(
  val memberKey: Long? = null // val memberKey: Long doesn't work, because it won't create a noarg default constructor - MyBatis doesn't work without a default constructor. Therefore, we have to supply a default value to it.
)

However, memberKey being nullable creates headaches in the business logic because !! or .? has to follow around all the frickin time.

Some people could recommend something like this:

class UserModel(
  val memberKey: Long = 0L
)

But, this creates another pack of worms since omitting memberKey by accident in the business logic will result in inserting a user with literally 0L memberKey, which leads us to validating != 0 manually in @Service or wherever appropriate.

What I would've done if Long wasn't a primitive is

class UserModel{
  lateinit var memberKey: Long
}

But alas, Kotlin, due to its infinite wisdom, has decided against supporting lateinit in primitives.

Any thoughts?

[Isaac Udy]

Does MyBatis support private constructors? If so, provide a secondary constructor that uses a default value of 0, and make that constructor private

[Isaac Udy]

Or, you could do the following:

data class MyClass(
    private val _id: Long = 0,
    ..., 
    ...
) { 
  val id: Long get() { 
     return if(_id == 0) throw RuntimeException() else id 
  } 
}

[James Richardson]

It's not kotlin related, but I am under the Impression that mybatis does not require a default constructor with the <constructor> tag or @Constructor annotation. May be wrong

[audriusk]

Maybe this would work in your case:

class UserModel {
    var memberKey: Long by notNull()
}

[Daniel]

Seems to be an architecture problem at first glance. The Problem shouldn't exist.

You have your MyBatis entities and then you use a converter to convert it to a model you use in your business logic.

This way you are free to worry about peculiarities of the persistence framework in your business code.

For example I hava a LevelRoomEntity
in my project which is the object saved by the room database and then I map/convert it to a Level which does not know anything about room

[Daniel]

So for MyBatis you can create a class with only a default constructor and public var fields if need be. This would be fine since it would never be used in business code

[Gyuhyeon]

Thanks for all the replies, I couldn't react promptly. As Daniel has pointed out, I do agree this is partly an architectural problem. To summarize, mybatis' peculiarity is forcing either a noarg constructor(have to provide default value to all fields) or a allarg constructor with everything neatly in order(not feasible in many cases) as far as I know. Separating entities with DTO does sound fair - it just hasn't been done in the codebase I'd been working on.
Any workaround to this does seem quite hacky.