javascript - How do I pass a Java Map<Long, Integer> into scala-play?

Question

In my play framework project I have a confirmed functional Java map of the form Java that is passed to a html page home.scala.html

The map variable is passed in as other (working) variables are, at the top of the page:

@(workingVar1: String, workingVar2: Int, mapVar: Map[Long, Integer])

But developer tools in google chrome highlights this part of the javascript (embedded in home.scala.html's head):

var myMap = @mapVar;

With the error Uncaught SyntaxError: Unexpected token =

So none of the javascript works. What is the correct way to pass this map in?

Answer 1

You can use Java/Scala variables in Twirl Scala templates and both are executed on the server side. Now on server side Twirl engine translates Java object to something (which probably isn't what you want) and in this form is passed to client, and then this JavaScript is executed.

You want to make sure that client will receive valid JavaScript code. To assign proper value, you will have to mix some JSON libraries, which will help you assign value in a proper way.

Eg. on the controller side:

...
Map<Long, Integer> map = new HashMap<>();
map.put(1L, 2);
map.put(3L, 3);
String yourMap = Json.stringify(Json.toJson(map));

Now you want to pass yourMap to view, and then you will assign to myMap using @Html as we want it as raw content fragment:

@(workingVar1: String, workingVar2: Int, mapVar: String)
var myMap = @Html(mapVar);

Try and let me know if it helped.