Subcut with GlobalSettings and Filters in the Play Framework

Quick post on an issue with Filters when using the Subcut template from activator.  If you use the Subcut template from TypeSafe Activator, and decide you want to use Filters on your Global object, you will likely run into this issue:

java.lang.ClassCastException: Global cannot be cast to play.GlobalSettings

or you will see that you can't call super.doFilter(next) as suggested in the documentation.

This is because there are two GlobalSettings classes in Play, one which is a Java class, and the other that is the Scala trait.  In most scala applications you will be extending a Scala trait. The Subcut template uses the Java class, and that's because the Subcut template relies on your Global being an instance, rather than a companion object, and the Scala GlobalSettings trait only works on an object, not an instance.

You can fix this problem by extending from both of these classes:

class Global extends GlobalSettings with play.api.GlobalSettings {

  override def doFilter(next: EssentialAction): EssentialAction = {
    Filters(super.doFilter(next), LoggingFilter)
  }

Thank goodness for traits!