hi there, I'm trying to use the kotlin-coroutines with Spring Boot, and everything seems to work nic...

# spring

[vilmos.nagy]

hi there,
I'm trying to use the kotlin-coroutines with Spring Boot, and everything seems to work nice util I add the @Transactional annotation to one of my spring service's method.
After the annotation is added some classCastException is thrown, see the details here: https://stackoverflow.com/questions/65331458/classcastexception-monoonerrorresume-cannot-be-cast-to-class-io-ebean-query

Is there a howto on how to use the kotlin-coroutines with spring transactions? thanks,

[sdeleuze]

Hi, which version of Spring Boot ? Are you using spring-boot-starter-web or spring-boot-starter-webflux ?

[vilmos.nagy]

• spring-boot: 2.4.0
• kotlin: 1.4.21
Aaaand I'm using the com.vaadin:vaadin-spring-boot-starter dependency, 'cause at the end the app is a Vaadin-based app.

[sdeleuze]

I think i fixed that in Boot 2.4.1

[vilmos.nagy]

I'm using this as an example to use the coroutines in Vaadin Routes: https://github.com/mvysny/vaadin-coroutines-demo/blob/master/src/main/kotlin/org/test/MainRoute.kt

[sdeleuze]

So please upgrade.

[vilmos.nagy]

give me a moment, and I'll try it 🙂

[sdeleuze]

But usually that means you try to use Coroutines/Reactive transaction with regular persistence which is not supported.

[sdeleuze]

So if you use Coroutines + @Transactional you should use Spring Data R2DBC or Spring Data Reactive NoSQL support with Coroutines extensions.

[vilmos.nagy]

oooookay.
even if the transaction is started in the coroutine and ended in the same coroutine as well?

[vilmos.nagy]

nice, it seems to work after the spring update.
let me turn on the verbose logging to double-check, but thanks for quick the help

[sdeleuze]

Even in that case yeah, if you are using Coroutines + transactions with non Reactive transaction manager I think transactions will simply not being used.

[sdeleuze]

Instead of the error you had before.

[vilmos.nagy]

okay, that's not so nice, and based on the verbose logging you're right.

[vilmos.nagy]

I'm trying to use the ORM called EBean - which I know, and IMHO 1 new thing is enough to learn in a pet project 🙂

is there a Reactive ORM in case I'll change my mind, and learn multiple new tools with this project?

[sdeleuze]

You should probably use it with Spring MVC and non suspending endpoints. Spring Data R2DBC is not a full fledge Reactive ORM but probably your best option.