We are building a site using AEM, where we have lot of forms (login, change address, change email) that will POST their data to an external system using web service. We had achieved this by using "slingServlet", where we used to get values using “sling.getParameter(“ ”). With this approach we are fixed with the form components used inside the particular forms.
For example login form, we are using username and password parameter, but in future we decided to add “dob” field too. To achieve this we need to do the code changes again. By doing so I believed we are not leveraging the CMS concept. So the question is there any other way to achieve this without doing code changes.