Play framework 2 : How to pass object between routes, views, and controller? - scala

Question

I'm trying to pass a book object from views to routes, and then send it to calculate in a controller. My code is following:
bookList.scala.html
#(books: java.lang.Iterable[Book])
#main("BookList"){
<div class="row">
#for(book <- books.iterator()){
<div class="col-sm-6 col-md-4">
<div class="thumbnail" style="height: 435px">
...
<p><a href="#routes.Application.buy(book)" class="btn btn-primary" role="button"
style="vertical-align:bottom">Order now!</a>
</div>
</div>
</div>
}
</div>
}
routes
...
GET /order controllers.Application.buy(book: models.Book)
...
However, It gave me an error : No QueryString binder found for type models.Book. Try to implement an implicit QueryStringBindable for this type.
I tried to change the routes as :
GET /order controllers.Application.buy(book)
It also returned an error :
type mismatch; found : String required: models.Book

Answer 1

That's not how Play routing works. The Play router parses variables from the URL or query string, and converts them to native types via the QueryBindable typeclass. You should have something more like this:
routes
GET /order/:bookid controllers.Application.buy(bookid: String)
And the action should be like:
Application.scala
def buy(bookid: String) = Action { request =>
// Look up book by id here.
Ok(views.html.thanks("you bought a book!"))
}
And the template like this:
bookList.scala.html
#for(book <- books.iterator()) {
...
<a href="#routes.Application.buy(book.id)" class="btn btn-primary"
}
Of course if your model's ID is other than String you need to modify the route's param type
Update -- alternative using form/POST
A form with a POST method is a better solution, or the user will buy another book each time they click the URL, and the id will be exposed. Check out the forms documentation. Your template would be like this:
#for(book <- books.iterator()) {
...
<form method="post">
<div>#book.name</div>
<input type="hidden" value="#book.id"/><button type="submit">buy</button>
</form>
}

Answer 2

You can't simple pass object (bean) as a url query parameter.
Default you can only define simple types as a parameter types. Please read carefully play's rounting documentation -> http://www.playframework.com/documentation/2.2.x/ScalaRouting especially Parameter types
But play framework has possibility to "learn" how to interpret specific url to bean.
You get info about this in error witch you posted. Responsible for this QueryStringBindable -> http://www.playframework.com/documentation/2.2.1/api/java/play/mvc/QueryStringBindable.html
In short like in documentation, when you define class like this:
class Book implements QueryStringBindable<Book> {
public String title;
public int numpages;
public Option<Pager> bind(String key, Map<String, String[]> data) {
if (data.contains(key + ".title" && data.contains(key + ".numpages") {
try {
title = data.get(key + ".title")[0];
numpages = Integer.parseInt(data.get(key + ".numpages")[0]);
return Some(this);
} catch (NumberFormatException e) {
return None();
}
} else {
return None();
}
}
public String unbind(String key) {
return key + ".title=" + title + "&" + key + ".numpages=" + numpages;
}
public String javascriptUnbind() {
return "function(k,v) {\n" +
" return encodeURIComponent(k+'.title')+'='+v.title+'&'+encodeURIComponent(k+'.numpages')+'='+v.numpages;\n" +
"}";
}
}
Then you can define route like:
GET /order controllers.Application.buy(p: Book)
You can then run in your browser e.g link:
localhost:9000/?p.title=SomeTitle&p.numpages=235
And in buy controller you will get p parameter as a Book class instance.
I did't test this code and this is in java. But you should get the idea.

Answer 3

You can define a custom PathBindable to automatically convert an id to a book object and pass it to buy method in controller. See PathBindable, another example
NOTE: I would define the PathBindable in same file as the Book model.

Answer 4

Simple example I used to parse in UUID's using PathBindable.
I'd rather not have to parse UUID's and ensure they're well formed in all controller/action code, so I use this at the router level. I used a UUIDP (P for param) to not pollute the UUID namespace.
Case Class and Parser
case class UUIDP(key: String, value: String, uuid: UUID)
object UUIDP {
implicit def pathBinder(implicit intBinder: PathBindable[String]) = new PathBindable[UUIDP] {
val uuidRegex = "([0-9A-Fa-f]{8}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{12})".r
override def bind(key: String, value: String): Either[String, UUIDP] = {
value match {
// sanity check, prevent errors, is this really a UUID?
case uuidRegex(c) => {
//error check too, binary value can be invalid
try { Right(UUIDP(key,value,UUID.fromString(value))) }
catch {
case ex : IllegalArgumentException => Left("Unparsable UUID")
}
}
case _ => Left("Invalid UUID Format")
}
}
// in case we need to remove this from the request
override def unbind(key: String, user: UUIDP): String = {
intBinder.unbind(key, user.value)
}
}
}
conf/routes
GET /items/:id #com.foo.MyController.getItem(id: UUIDP)
Controller
def getItem(sessionId: UUIDP) = Action(parse.text) { request =>
Ok(s"Fetching item [${sessionId.uuid}]")
}