Play Framework 2 Bind form from request

I am new to Play2 (I've already developed a project using Play1) and I have problems with form binding from request. The documentation about forms is really light. Here is the code of my controller : ``` private final static Form<Estimation> estimationForm = form(Estimation.class); /** * Get an estimation by form * @return */ public static Result estimation() { return ok(views.html.rate.estimation.render( estimationForm, City.findAll() )); } /** * Display estimation results * @return */ public static Result results() { if (request().method().equals("POST")) { Form<Estimation> form = estimationForm.bindFromRequest(); if (form.hasErrors()) { System.out.println(form.errorsAsJson().toString()); return ok(views.html.rate.estimation.render( form City.findAll() )); } else { System.out.println(form.get()); return ok(views.html.rate.results.render( )); } } else { return estimation(); } } ``` I display cities in a select as this : ``` <select id="city" name="city"> <option value="1">Paris, France</option> <option value="2">Lyon, France</option> <option value="3">Marseille, France</option> <option value="4">Barcelona, Spain</option> <option value="5">Berlin, Germany</option> </select> ``` When I submit the form, I have the following error : {"city":["Invalid value"]} So here is my question : The binder seems to work well with simple fields (for example a String property in my model), but what about @ManyToOne relationships ? Thank you.