A modern programming language that makes developers happier.

kotlinlang

I don't know if this channel is actively used, but let's try.

I'm facing an issue where Kotlin JPA classes are behaving unexpected and different than the Java likes.

It has to do with proxies and @Id columns of associations

E.g. when having a `Country` association `Continent` like:

```
@Entity
class Country(
        @Id
        var id: String,
        var alpha2Code: String,
        var alpha3Code: String,
        var name: String,
        @ManyToOne(fetch = FetchType.LAZY)
        @JoinColumn(name = "continent_id")
        var continent: Continent
)
```

```
val country = countryRepository.findById("netherlands").get()
assertEquals("europe", country.continent.id)
```

now, this call to `country.continent.id` should not cause the continent to be fetched, but with above Kotlin it is (causing additional query).

the Java equivalent (or what comes close to it) is not doing the additional continent query.

See also SO discussion: <https://stackoverflow.com/questions/53466913/how-to-avoid-initializing-a-hibernate-proxy-when-only-the-entity-id-is-needed>

and a sample project (with Kotlin and Java) I created: <https://github.com/marceloverdijk/hibernate-proxy-id>

Does somebody know this could be related to the Kotlin generated bytecode and/or the Kotlin JPA compiler plugin?

Note I have created <https://youtrack.jetbrains.net/issue/KT-28525> for this.

anyone know how to do this? <https://stackoverflow.com/q/55226704/206466>

Are most people using non-data classes, and var instead of vals for their Entities?

I can’t speak for most people but I’m using data classes, and val, no problems so far (well after generating the default constructors)

I am as well, though after seeing the guidelines in these links I'm concerned about the issues with hashCode/equals in particular <https://spring.io/guides/tutorials/spring-boot-kotlin/> <https://twitter.com/sdeleuze/status/1096423498325651459> <https://kotlinexpertise.com/hibernate-with-kotlin-spring-boot/>

:thinking_face: I posted a question in <#C0B8ZTWE4|spring> regarding delegates to build entities; maybe I should've posted it here?

Hey y’all.
Anyone know if you can use `value class` as an `@Id` field?
First our integration test was complaining that the class wasn’t Serializable (on save), after we fixed that we got an error on retrieval saying something about an Invalid Type.

OOC - is there any easy way to combine Flyway and JPA to manage generated migrations

Figured this out btw - lmk if anyone needs assistance on thsis