First of all my question may not be relate to Kotlin,, Why

QueryRunner().query()

return

Long

, is it depending on what Handler is using? For example my code is like this

val query = "SELECT COUNT(*) FROM goods_user_rel WHERE _goods_id = ?"
val count = QueryRunner().query(connection, query, ScalarHandler<Long>(), goodsId)

The first time i wrote

ScalarHandler<Int>()

and i got error something likes

java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer

Then i change

ScalarHandler<Int>()

to

ScalarHandler<Long>()

and it’s work but i have no idea why

Long

is return

I’m not really sure about QueryRunner, however coming from JPA, it is by specification that COUNT query must return data in LONG instead of INT. I believe it’s related in any way.