How can I use params in a before filter in Scalatra?

Question

I have a global filter that I would like to implement in my scalatra based API. For the sake of simplicity, I want ANY API call that has a variable foo with a value bar to throw a 403. I started this problem with an inheritance chain.

class NoFooBarRouter extends ScalatraServlet{
    before() {
        if(params.getOrElse("foo", "") == "bar") //params is empty here. 
            halt(403, "You are not allowed here")
        else
            pass()
    }  
}

class APIRouter extends NoFooBarRouter{
    get("/someurl/:foo") {
        "Hello world!"
    }        
}

This does not work. During the debug process, I noticed that the params variable is always empty regardless of whether there is a param or not. Is there a better approach or is there another method to extract the params from the before filter?

Answer 1

The params are not filled out during the before method. You can override the invoke method.

class NoFooBarRouter extends ScalatraServlet{
    override def invoke(matchedRoute: MatchedRoute): Option[Any] = {
        withRouteMultiParams(Some(matchedRoute)){
            val foo = params.getOrElse("foo", "")
            if(foo =="bar")
                halt(403, "You are not authorized for the requested client.")
            else
                NoFooBarRouter.super.invoke(matchedRoute)
        }
    }
}