README.md

beer-store-service-kotlin-javalin-ktorm-liquibase

Sample service using kotlin on backend and other fancy things.

• Javalin as service controller
• Ktorm as ORM and query builder
• HikariCP for database pooling and connection
• Liquibase for database migrations

Project requires Java 11 or newer to run

How do I run this

It uses gradle as build tool, so:

gradle run

will build the project and run it.

You also can open the project on Intellij Ultimate, everything will feel like home :-)

Trivia

Liquibase and HikariCP aren't kotlin-native libraries. However, one of biggest kotlin advantages is to be able to use everything java ecosystem has to offer.

Unlike other fancy migration tools, Liquibase does not offer a tool to create migrate templates. I covered it in this article about what liquibase can do.

jackson and ktorm had a fight

jackson had a difficult time serializing ktorm proxies when I used the recommended strategy for object-relational mapping. I've left Media mapping as an example of what ktorm recommends.

However, javalin endpoint keeps throwing exceptions and no research produced a solution. This configuration must be made in order to make jackson understand how to deal with ktorm proxies.

Except when I used the alternative mapping method offered by ktorm:

package beer.store.models

import org.ktorm.dsl.QueryRowSet

import org.ktorm.schema.*

import java.time.LocalDateTime

// https://www.ktorm.org/en/entities-and-column-binding.html
// https://www.ktorm.org/en/define-entities-as-any-kind-of-classes.html
data class Beer(
    var idBeer: Int?,
    var creationDateBeer: LocalDateTime?,
    var titleBeer: String?,
    var descriptionBeer: String?,
    var idMedia: Int?,
)

object Beers : BaseTable<Beer>("beer") {
    var idBeer = int("idbeer").primaryKey()
    var creationDateBeer = datetime("creationdatebeer")
    var titleBeer = varchar("titlebeer")
    var descriptionBeer = varchar("descriptionbeer")
    var idMedia = int("idmedia")

    override fun doCreateEntity(
        row: QueryRowSet,
        withReferences: Boolean
    ) = Beer(
        idBeer = row[idBeer],
        creationDateBeer = row[creationDateBeer],
        titleBeer = row[titleBeer],
        descriptionBeer = row[descriptionBeer],
        idMedia = row[idMedia]
    )
}

Mapping got way more verbose, but it doesn't use dynamic proxies anymore and then jackson started to work again.

So far the least pleasant ORM framework is ktorm.

Would I use this in production

Kotlin/Javalin/Liquibase? Sure!