Redirect to referer after a POST Request - scala

Question

I have a web application in Play. The web application consists of several pages. In every page there is a small flag that enables the user to change the language (locale) from german to english and back.
I handle this with a redirect to referer:
def referer(implicit request: Request[AnyContent]) =
request.headers.get(REFERER).getOrElse(mainUrl)
def locale(l: String) = Authenticated { user =>
implicit request =>
Redirect(referer).withCookies(Cookie(LANG, if (l == "de" || l == "en") l else "de"))
}
It is working fine. Well, at least for GET requests.
I have a specific page where the user has to input data in a form. This form is then POSTed to the server. Were errors found, the form is displayed again with the error messages, as usual. Now, if the user wants to change the language (by clicking on the flag), the redirect to referer does not work, because it tries to use a GET request, and Play complains that a GET route does not exist for this method (which is true).
I am solving this by caching the form and defining another method where the form is taken from the cache:
# User data is POSTed to the server
POST /create/insert controllers.MyCreate.insert()
# After a redirect the cached form is displayed again
GET /create/insert controllers.MyCreate.insertGet()
It works, but I don't like this solution. It does not seem normal to have to create another entry in the routes and another method just to adress this problem. I would need to add this hack for every POST route in my application!
Is there a more elegant solution to this?

Answer 1

You could change it into something like this (untested):
def changeLang(lang:String, returnUri:String) = Action {
Redirect(returnUri)
.withCookies(Cookie(LANG, if (lang == "de" || lang == "en") lang else "de"))
}
In you template you would output the route to changeLang in the link, you can get the uri via the request
#routes.Application.changeLang("en", request.uri).url
I suggest you make request implicit in your action and define it as implicit in your template so you don't need to pass it on to each template.
// in the controller
def myUrl = Action { implicit request =>
Ok(views.html.myTemplate("something"))
}
// in the template
#(title:String)(implicit request:play.api.mvc.RequestHeader)
Edit
As for the POST requests, it common (for these types of framework) to have POST requests simple handle stuff and then redirect to another page. The usual flow is like this:
Form submits to a handler
Handler does something with the form information
Handler redirects to a page
An example:
// Hooked up to a GET route
def edit(id:Long) = Action {
// render the view with a form that displays the element with given id
// if the flash scope contains validation information, use that in display
}
// Hooked up to a POST route
def editHandler = Action {
// validate the form
// if validation succeeds
// persist the object
// redirect to edit
// else
// put the form information into the flash scope
// put any validation messages into the flash scope
// redirect to edit
}
If you do not want to use this flow you need to have both a GET and POST route anyway. The user might do a page reload on the resulting page.