Cannot use Siena model objects with Query fields on Groovy templates

[dmoebius]

Consider the following model class:

@Table("units")
public class Unit extends Model {
  @Id public Long id;

  @Filter("unit")
  public Query<Entry> entries;
}

If you try to put an instance of this class into the params map and use it in a Groovy/HTML template:

public static void edit(Long unitId) {
  Unit unit = Unit.getByKey(unitId);
  notFoundIfNull(unit, "unit " + unitId);
  render(unit);
}

#{extends 'main.html' /}
#{set title:'Edit Unit ${unit.name}' /}
<h1>Edit Unit ${unit.name}</h1>

then Play fails to serialize ("unbind") the class because it runs into an infinite recursion when trying to serialize the Query field. Eventually it throws a StackOverflowException.

The reason is because Play serializes the Unit instance into a map of json keys like this:

unit.entries.obj = ...
unit.entries.obj.entries = ...
unit.entries.obj.entries.obj = ...
unit.entries.obj.entries.obj.entries = ...
unit.entries.obj.entries.obj.entries.obj = ...

... and so on forever.

A solution for the play-siena plugin might be to override the unBind() method in SienaPlugin to ignore Query fields altogether:

@Override
public Map<String, Object> unBind(Object src, String name) {
  if (siena.Query.class.isAssignableFrom(src.getClass())) {
    return new HashMap<String, Object>();
  }
  return null;
}

Please evaluate.