server routes & modules

A RouteSpec needs to be bound to a standard Finagle Service to receive requests, in order to create a ServerRoute. Since Finagle services are very lightweight, we can create a new instance of the Service for every request, and bind the RouteSpec to a factory method which receives the dynamic Path parameters and returns the Service. Other parameters can be retrieved directly in a type-safe manner from the HTTP request by using <--() or from() method on the parameter declaration.


The presence and format validity of ALL parameters which are attached to a RouteSpec is verified by Fintrospect before requests make it to this bound Service, so no validation code is required. The response returned to the client is:

  • Not Found 404: if there are any Path params which are missing or invalid (all are required)
  • Bad Request 400: if there are any Header, Query, or Body params are missing (required only) or invalid

simple example

val holidays = Query.required.*.localDate("datesTakenAsHoliday")
val includeManagement = Header.optional.boolean("includeManagement")

def findEmployeesOnHoliday(departmentId: Integer) =[Request, Response] {
  request =>
    val holidayDates: Seq[LocalDate] = holidays <-- request
    val includeManagementFlag: Option[Boolean] = includeManagement <-- request
    val response = Response(Ok)
    val baseMsg = s"Everyone from department $departmentId was at work on $holidayDates"
    response.contentString = baseMsg + (if (includeManagementFlag.getOrElse(false)) "" else ", even the management") Future(response)

val route = ServerRoute[Request, Response] = 
  .at(Method.Get) / "employee" / Path.integer("departmentId") bindTo findEmployeesOnHoliday


A Module is a collection of ServerRoute that share a common URL context, which is built up from the Root object. Add the routes and then convert into a standard Finagle Service object which is then attached in the normal way to an HTTP server.

def listEmployees(): Service[Request, Response] = => Future(Response()))

  RouteModule(Root / "employee")
    .withRoute(RouteSpec("lists all employees").at(Method.Get) bindTo listEmployees)

Modules with different root contexts can also be combined with one another and then converted to a Service:

RouteModule(Root / "a").andThen(RouteModule(Root / "b")).toService

self-describing Module APIs

A big feature of the Fintrospect library is the ability to generate API documentation at runtime. This can be activated by passing in a ModuleRenderer implementation when creating the RouteModule and when this is done, a new endpoint is created at the root of the module context (this location is overridable) which serves this documentation.

Bundled with Fintrospect are:

  • Swagger (1.1 and 2.0) JSON, including JSON Schema models
  • A simple JSON format
  • Sitemap XML format

Other implementations are pluggable by implementing the ModuleRenderer trait - see the example code for a simple XML implementation.

val service = RouteModule(Root / "employee", Swagger2dot0Json(ApiInfo("an employee discovery API", "3.0"))).toService
Http.serve(":8080", new HttpFilter(Cors.UnsafePermissivePolicy).andThen(service))

Note above the usage of the Finagle CorsPolicy filter, which will allow the services to be called from a Swagger UI - without it, the server will reject any cross-domain requests initiated inside a browser.


Module routes can secured by adding an implementation of the Security trait - this essentially provides a filter through which all requests will be passed. An ApiKey implementation is bundled with the library which return an 401 Unauthorized HTTP response code when a request does not pass authentication.

RouteModule(Root / "employee")
.securedBy(ApiKey(Header.required.string("api_key"), (key: String) => Future(key == "extremelySecretThing")))