According to Servlet Specification 2.2, which is the latest, it is specified that "All the data from both the query string and the post body are aggregated into the parameter set. The order of this aggregation is that query string data takes precedence over post body parameter data."So what you are getting is quite valid and well supported by the specs.
In JSDK2.1, in case a parameter has multiple values, the specs require the getParameter() to return the first value of the array returned by getParameterValues().
Please match this explanation by the version of API's you are using.
Regards
Mahendra
