protected Response handleRequest(HttpHeaders headers, String body, UriInfo uriInfo,
                                   Request.Type requestType, ResourceInstance resource) {

    return handleRequest(headers, body, uriInfo, requestType, null, resource);
  }
Requests are funneled through this method so that common logic can be executed.
Creates a request instance and invokes it's process method.  Uses the default
media type.

@param headers      http headers
@param body         http body
@param uriInfo      uri information
@param requestType  http request type
@param resource     resource instance that is being acted on

@return the response of the operation in serialized form
ambari-server/src/main/java/org/apache/ambari/server/api/services/BaseService.java