Showing how to use Swagger annotations to mark a parameter as required.

swagger-annotations.java

@PUT
  @Path("/{id}")
  @Produces(value = {"application/json", "application/xml"})
  @ApiOperation(value = "Update/Modify ToDo entity specified by 'id'", produces = "application/json, application/xml", 
                response = ToDo.class, consumes = "application/xml, application/json")
  @ApiResponses({
    @ApiResponse(code = SC_INTERNAL_SERVER_ERROR, message = "SERVER ERROR"),
    @ApiResponse(code = SC_BAD_REQUEST, message = "Invalid ID value")
  })
  public ToDo updateToDo(@ApiParam( value = "The unique ID of the ToDo entity", name = "id", required = true) @PathParam("id") Long id, 
                                    ToDo item) {
    ToDo todo = dao.updateToDo(item);
    if (todo==null) {
      throw new WebApplicationException(String.format("Unable to update item with id '%d'", id), BAD_REQUEST);
    }
    return todo;
  }