How to set header to return an excel file as reponse and download with specified name without creating temporary .xls file at server

Question

I am using below code for the same.

@POST
@Path("getExelStreamDocDB")
@Produces("application/vnd.ms-excel")
public Response getExelStreamDocDB(String req);

Implementation of above service containing below piece of code.

byte[] encoded = Base64.getEncoder().encode(bytes);
ResponseBuilder responseBuilder = Response.ok((Object) encoded);
responseBuilder.header("Content-Disposition", "attachment; filename=\"Provider.xls\"");

I am using Apache POI to create XLS file . Please help.