Hello! I'm having some issues when trying to add c...

# spring

[Leonardo Borges]

Hello! I'm having some issues when trying to add custom headers to a HttpServletResponse within a suspend function.
The approach we are using now is not good, so we would like to find a proper solution:

@GetMapping("/users")
suspend fun getUsers(//...parameters, response: HttpServletResponse): List<UsersResource> {
    val users = userService.searchBy(//parameters)
    response.addPaginationHeaders(users.size)
    return users
}

For instance, addPaginationHeaders will be changed only for example purposes, as below:

internal fun HttpServletResponse.addPaginationHeaders(size: Int) {
    val uri = ServletUriComponentBuilder.fromCurrentRequest().toUriString()
    setHeaders("X-Count", size)
    //...other params
}

So, suspend function doesn't work (throws java.lang.IllegalStateException: No current ServletRequestAttributes).
Instead, we have to place the function body within a runBlocking to make it work.

suspend fun getUsers(\\...parameters, response: HttpServletResponse) = runBlocking {
    //same code as above
}

Has anyone experienced this issue? Is there any solution besides runBlocking?

[sdeleuze]

Interesting, let me have a look.

[efemoney]

It seems like the servlet context isnt getting propagated from one thread to the other after the suspend function userService.searchBy returns

[efemoney]

I havent looked at how spring is calling the suspend handler functions but it seems the solution would be to add the servlet context (and any other thread based contexts spring relies on eg MDC, ReactorContext[which is set automatically afaik] etc) as `ThreadContextElement`s to the coroutine, so that they are copied through all of the threads that coroutine runs on

[sdeleuze]

Yeah likely this kind of issue

[sdeleuze]

I want to try with Mono to see if that's Coroutines specific or not.

[sdeleuze]

I am not able to reproduce the issue.

[Leonardo Borges]

is this the right approach to propagate the context to he coroutine? https://blog.jdriven.com/2021/07/propagating-the-spring-securitycontext-to-your-kotlin-coroutines/

[Leonardo Borges]

since it has a ContextHolder, sounds easier to manage states. but could not find anything looked like to servlet context