show an example model for Map in swagger for java endpoint

Question

I have

@POST
@Path("/path-to-call")
@Timed
@ActionRequired("my path-to-call")
@ApiOperation("description of call")
@Produces(MediaType.APPLICATION_JSON)
public Response processmyCall(Map<String, String> requestBody) throws Exception{

but swagger shows with {} as the model.

how do i tell it to show

{"val":"<data>","val":"<data>"}