Each workspace can have published parameters associated with them. However, the Web Services API does not provide any means of determining the published parameters associated with a workspace. Therefore, you must hard-code the published parameter values and input types into your web application. However, if someone re-uploads their workspace and adds, removes or updates a published parameter, these changes will not be reflected in your application.
Fortunately, you can make your application dynamic by using the REST API. For an example application that requests the parameters associated with a workspace and builds a form dynamically, see: REST Service.
Further examples can be found in the REST playground: http://fmeserver.com/userweb/sharper/playground/index.html.