hi, folks! I have a question about `is` checks and...

# server

[August Lilleaas]

hi, folks! I have a question about is checks and delegation from a class to an object. Ktor has an extension function on ApplicationRequest that uses when(this) to check if the request is a ServletApplicationRequest. The problem is that the actual request object that I call the extension function on, is a RoutingApplicationRequest, which is a class that delegates to the original request object. Which in turn causes is ServletApplicationRequest to be false, as is only seems to check class inheritance hierarchies, and not delegation. Is there a way to work around this? Or is it an issue/bug that Ktor needs to handle differently to work as expected?

FYI, here’s the full extension function:

public val ApplicationRequest.javaSecurityPrincipal: Principal?
    get() = when (this) {
        is ServletApplicationRequest -> servletRequest.userPrincipal
        else -> null
    }

and here’s the class that the instance of the request object is a member of:

public class RoutingApplicationRequest(
    override val call: RoutingApplicationCall,
    override val pipeline: ApplicationReceivePipeline,
    request: ApplicationRequest
) : ApplicationRequest by request

[Emil Kantis]

A ServletApplicationRequest is a ApplicationRequest , but the inverse isn't necessarily true.

[Emil Kantis]

If your original request in RoutingApplicationRequest is always a ServletApplicationRequest you should model it as such and I think it should work then.

[August Lilleaas]

seems like this is an issue that needs to be fixed by ktor - there’s no way to access the original servlet request the way Ktor wraps it and delegates to it.

I filed an issue 🙂

https://youtrack.jetbrains.com/issue/KTOR-4784

[Emil Kantis]

You could probably solve it with a slight workaround:

public val RoutingApplicationRequest.routedJavaSecurityPrincipal: Principal?
    get() = when (this.request) {
        is ServletApplicationRequest -> (this.request as ServletApplicationRequest).javaSecurityPrincipal
        else -> null
    }