Why can't I mix HTTPContext with QUERY or PATH parameters in an EK9 service method?

← Web Services · Ref: Q1330

When an EK9 service method binds the full request via :=: CONTEXT, the HTTPContext parameter must be the ONLY parameter. HTTPContext already exposes the complete request - query string, path segments, headers, body - so adding individual :=: QUERY or :=: PATH bindings alongside it is redundant and ambiguous, raising E07792.

You have two valid choices:
1. Use HTTPContext ALONE and extract everything you need from it inside the method body via its request accessors.
2. Use only individual qualified parameters (:=: PATH, :=: QUERY, :=: HEADER, :=: CONTENT) and do NOT take an HTTPContext at all.

See Q202 for parameter binding and Q945 for parameter qualifiers.

Example

defines module qa.webdeep.service.httpcontext

  defines constant

    JSON_TYPE <- "application/json"

  defines service

    <?-
      Search service demonstrating the correct use of HTTPContext.
      The method binds the full request via :=: CONTEXT and uses ONLY
      that single parameter. Any query or path values are read from the
      context inside the method body - never via a second :=: QUERY/PATH
      binding, which would raise E07792.
    -?>
    SearchService :/search open

      search() as GET for :/results
        -> ctx as HTTPContext :=: CONTEXT
        <- response as HTTPResponse: (reqId: ctx.requestId()) with trait HTTPResponse
          override content()
            <- rtn as String: `{"requestId": "${reqId}"}`
          override status() as pure
            <- rtn as Integer: 200
          override contentType() as pure
            <- rtn as String: JSON_TYPE
          override cacheControl() as pure
            <- rtn as String: "no-cache"
          override contentLanguage() as pure
            <- rtn as String: "en"
          default operator ?

  defines application

    SearchApp
      register SearchService()

  defines program

    HttpContextDemo()
      stdout <- Stdout()
      stdout.println("HTTPContext must be the ONLY service-method parameter.")
      stdout.println("Read query and path values from the context inside the body,")
      stdout.println("never via a second :=: QUERY or :=: PATH binding (E07792).")

Common mistakes

E07792 — HTTPContext (:=: CONTEXT) already provides the entire request, so adding a second :=: QUERY binding alongside it is redundant and ambiguous, triggering E07792. See ek9 -h E07792 for details.

Incorrect:

        ->
          ctx as HTTPContext :=: CONTEXT
          term as String :=: QUERY "q"

Correct:

        -> ctx as HTTPContext :=: CONTEXT

Other ways to ask this

What triggers E07792 HTTPContext mixed with other params?
Why must HTTPContext be the only parameter in a service method?
How do I access query and path values when using HTTPContext in EK9?

Coming from another language?

Java Spring: you may freely combine HttpServletRequest with @RequestParam/@PathVariable in the same handler - no compiler objection, even though the request object already contains those values. JAX-RS allows @Context HttpServletRequest beside @QueryParam. EK9 instead makes the redundancy a compile-time error (E07792): the all-encompassing HTTPContext and individual bindings are mutually exclusive, so a method has exactly one, unambiguous binding strategy.

Keywords: CONTEXT, PATH, QUERY, service, E07792, HTTPContext, binding, web, parameter