It would be really nice to be able to have a result like:
Where actionMessages is the result of getActionMessages() from a ValidationAware action, and has more than one message.
And have that generate a url like: http://myco.com/doit.action?actionMessages=Message+1&actionMessages=Message+2
Rather than convert the result into the toString of the collection which then can't be interpreted by struts on the other end as a collection.
Looking at ServletRedirectResult.doExecute(), it does use urlHelper.buildParametersString() which is array/iterable aware, so the trick would be to allow the parsing of the parameter value to be a String or Iterable<String> (and have the ParsedValueEvaluator run against the contents).
We'd probably only want to support this functionality for the ServletActionRedirectResult even though it would have to be implemented at the ServletRedirectResult layer.