is there any documentation on how to fully use coroutines+Spring (reactive)? What i do know is that ...

# spring

[thana]

is there any documentation on how to fully use coroutines+Spring (reactive)?
What i do know is that in principal everything should work. but when it comes to db transactions or spring security i feal unsure about how to handle the reactor Context, how it interacts with the corouting context and what i do have to do in order everything works or what does already work ootb.

[nicholasnet]

For database I would suggest to look at https://docs.spring.io/spring-data/r2dbc/docs/1.1.4.RELEASE/reference/html/#reference

[Joel]

@thana are you building a web server? Using WebFlux?

[Joel]

Database calls are often blocking (if not using r2dbc). Wrap any blocking code in withContext(<http://Dispatchers.IO|Dispatchers.IO>) to offload them to a thread pool specifically for this purpose. The only gotcha I have found in spring-security is that method authorization (i.e. @PreAuthorize, etc) are not compatible with suspending functions. But it's easy enough to wrap with a mono i.e. fun index() = mono { // now I am in a suspended context }.

[thana]

@Joel so you mean in spring security suspending are not supported yet but methods returning a reactive type are, so annotations work with them?

[Joel]

Yes. Have not had any issues using asynchronous code w/ spring-security. Just that nit when it comes to method security.

[Joel]

The recently released kotlin security DSL is really slick btw

[Gary]

See https://www.baeldung.com/spring-boot-kotlin-coroutines

[sdeleuze]

Not yet official guide but that's planned.

[sdeleuze]

For now you can check https://github.com/sdeleuze/spring-boot-coroutines-demo for the web part.

[sdeleuze]

For the persistence I would advise to use Spring Boot 2.4.x integratio of R2DBC or Spring Data Reactive NoSql bits with Coroutines extensions.

[sdeleuze]

If you need to use regular Spring Data API (not Coroutines based natively) or other solution like jOOQ that's probably that you should use Spring MVC not WebFlux.

[sdeleuze]

See related comment I posted on Reddithttps://www.reddit.com/r/java/comments/jw0jsx/java_springboot_webflux_quandary/gen7i34/?utm_source=reddit&utm_medium=web2x&context=3

[sdeleuze]

If you have more specific question please let me know.

[thana]

I think all the fear that came up in me stems from the fact, that for almost 20 years i was used to implicitly rely on the one-thread-per-requests-semantics which now falls apart and i realize how much i was relying on alle the magic happening in the background. realizing that i finally the feeling emerges to understand what was taken for granted all the time before

[sdeleuze]

Yeah i can understand that feeling. We have introduced Reactor context with Coroutines interop in order to continue to use security and transactions in that Reactive/Coroutines context.

[thana]

@sdeleuze yeah read that and i;m eager to understand 🙂