redirectToNoTrailingSlashIfPresent

Signature

def redirectToNoTrailingSlashIfPresent(redirectionType: StatusCodes.Redirection): Directive0

Description

If the requested path does end with a trailing / character, redirects to the same path without that trailing slash..

Redirects the HTTP Client to the same resource yet without the trailing /, in case the request contained it. When redirecting an HttpResponse with the given redirect response code (i.e. MovedPermanently or TemporaryRedirect etc.) as well as a simple HTML page containing a “click me to follow redirect” link to be used in case the client can not, or refuses to for security reasons, automatically follow redirects.

Please note that the inner paths MUST NOT end with an explicit trailing slash (e.g. "things"./) for the re-directed-to route to match.

A good read on the subject of how to deal with trailing slashes is available on Google Webmaster Central - To Slash or not to Slash.

See also redirectToTrailingSlashIfMissing which achieves the opposite - redirecting paths in case they do not have a trailing slash.

Example

Scala
import akka.http.scaladsl.model.StatusCodes

val route =
  redirectToNoTrailingSlashIfPresent(StatusCodes.MovedPermanently) {
    concat(
      path("foo") {
        // We require to not have a trailing slash in the path
        complete("OK")
      },
      path("bad"./) {
        // MISTAKE!
        // Since inside a `redirectToNoTrailingSlashIfPresent` directive
        // the matched path here will never contain a trailing slash,
        // thus this path will never match.
        //
        // It should be `path("bad")` instead.
        ???
      }
    )
  }

// tests:
// Redirected:
Get("/foo/") ~> route ~> check {
  status shouldEqual StatusCodes.MovedPermanently

  // results in nice human readable message,
  // in case the redirect can't be followed automatically:
  responseAs[String] shouldEqual {
    "This and all future requests should be directed to " +
      "<a href=\"http://example.com/foo\">this URI</a>."
  }
}

// Properly handled:
Get("/foo") ~> route ~> check {
  status shouldEqual StatusCodes.OK
  responseAs[String] shouldEqual "OK"
}

// MISTAKE! will never match - reason explained in routes
Get("/bad") ~> route ~> check {
  handled shouldEqual false
}
Java
import static akka.http.javadsl.server.Directives.complete;
import static akka.http.javadsl.server.Directives.path;
import static akka.http.javadsl.server.Directives.redirectToNoTrailingSlashIfPresent;
final Route route =
    redirectToNoTrailingSlashIfPresent(
        StatusCodes.MOVED_PERMANENTLY, () ->
        concat(
            path("foo", () -> complete("OK")),
            path(segment("bad").slash(), () ->
                // MISTAKE!
                // Since inside a `redirectToNoTrailingSlashIfPresent` directive
                // the matched path here will never contain a trailing slash,
                // thus this path will never match.
                //
                // It should be `path("bad")` instead.
                 complete(StatusCodes.NOT_IMPLEMENTED)
            )
        )
    );
// tests:
testRoute(route).run(HttpRequest.GET("/foo/"))
    .assertStatusCode(StatusCodes.MOVED_PERMANENTLY)
    .assertEntity("This and all future requests should be directed to " +
      "<a href=\"http://example.com/foo\">this URI</a>.");

testRoute(route).run(HttpRequest.GET("/foo"))
    .assertStatusCode(StatusCodes.OK)
    .assertEntity("OK");

testRoute(route).run(HttpRequest.GET("/bad"))
    .assertStatusCode(StatusCodes.NOT_FOUND);
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