Angular 2+ - Handle JAVA Rest 401 response - json

Question

Angular service.ts:
getExcel() {
let link: string = (this.url);
return link;
}
component.ts:
public getExcel() {
//checks if string is empty, undefined or not null
if (this.langCode) {
return window.open(this.avrs.getExcel());
}
}
Java rest.java
#GET
#Path("/excel")
#Produces("application/vnd.ms-excel")
public Response getTransportCostsExcel(
#Context HttpServletRequest request,
) {
byte[] excelInBytes = excelGen.getExcel();
if(excelInBytes == null){
return Response.status(Response.Status.NOT_FOUND).entity("No data").build();
}
//Header details
String contentType = "application/vnd.ms-excel";
Response.ResponseBuilder responseBuilder = javax.ws.rs.core.Response.ok((Object) excelInBytes);
responseBuilder.type(contentType);
responseBuilder.header("Content-Disposition", "attachment; filename=" + fileName);
//Returns Excel
return responseBuilder.build();
}
When I try calling my api from postman i get "No data" and status is 401 not found. So the rest method works fine.
I get my excel file if data is found. But I can't seem to handle the 401 response. Angular opens a new window and says
site not avaliable: ERR_INVALID_RESPONSE
As you can see im not using http.get cause I want the user to start downloading the excel if the file is found.