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s

sreich

06/21/2022, 8:30 PM
are there recommendations for moving from Java to Kotlin for hibernate? in particular, i'm trying to get the best null safety i can get... There is this https://medium.com/swlh/defining-jpa-hibernate-entities-in-kotlin-1ff8ee470805 but...my issue is, if i set nullable=false...that should be a @nonnull object, because i know it's an impossibility for it to happen in my scenarios. How can I get that though? do I need to use lateinit here?
m

Mikhail

06/21/2022, 11:56 PM
You can take a look at how i do it: https://github.com/linda-project/linda/blob/main/src/main/kotlin/dev/d1s/linda/entity/shortLink/ShortLink.kt I use constructors in most cases
👍 1
I wouldn't recommend using
lateinit
on JPA entities
s

Szymon Jeziorski

06/22/2022, 12:00 PM
The medium article you provided does not consider existing kotlin jpa plugin which in my opinion is the critical go-to when working with Kotlin and JPA (start.spring.io includes it by default when you link Spring Data dependency) - with it you could write your classes as you would normally do it in Kotlin, preserving null-safety, immutability etc. and the plugin will take care of generating complaint bytecode. Sample article about it: https://www.baeldung.com/kotlin/jpa
👍 1
s

sreich

06/22/2022, 12:55 PM
@Szymon Jeziorski yep that sounds nice to me. So, they have to use the ctor init to do this, right? not exactly pretty if you've got a 20 column entity with annotations everywhere and mappings
but there are worse things.
@Mikhail i'm surprised you don't just use lombok. Implementing your own hashcode/equals/string all the time is so much duplication versus @ToString @Equals
m

Mikhail

06/22/2022, 12:58 PM
I don't use lombok in my kotlin projects
Simply because there are problems with it
s

sreich

06/22/2022, 12:59 PM
seems that there is kapt or the lombok plugin. but i'm unfamiliar with what kinda problems there might be
s

Szymon Jeziorski

06/22/2022, 1:11 PM
@sreich I'm not sure if I understand you correctly, but you yourself don't have to write a no-arg constructor for entities, and the one generated by the plugin is only to be called via reflection. You can read about it here: https://kotlinlang.org/docs/no-arg-plugin.html If you meant that having a single large constructor is a must (which can be ugly for entities with many fields) then it isn't - from the code perspective, you can work with entities as with other classes and use factory methods, secondary constructors, custom builders or whatever suits you. And as a side note, I also don't use Lombok for Kotlin projects. For model classes I usually use data classes that provide equals, hashCode, and toString out of the box and for JPA entities I usually have a single MappedSuperclass having equals and hashCode implementation. I hardly ever need custom toString for JPA Entities. All in all, I couldn't work with Java without Lombok but don't need when working with Kotlin
t

Thomas

07/04/2022, 4:53 PM
A late notice: you may also check bootify.io for a Spring Boot app with database model, also not using dataclasses because it's creating problems