To add a locale to Jasperserver you need to open the applicationContext-security.xml file. This is located in the WEB-INF folder.
To test your web service, you can use Smock. Smock compares your request with the response by XML files. You just need a response.xml file with your response and a request.xml file with your request.
How to convert a Date to an XMLGregorianCalendar
GregorianCalendar c = new GregorianCalendar();
XMLGregorianCalendar xmlDate = DatatypeFactory.newInstance().newXMLGregorianCalendar(c);