code: protected String getRequestHost() {
          String forwarded = header("X-Forwarded-Host");
          if (StringUtil.blank(forwarded)) {
              return host();
          }
          String[] forwards = forwarded.split(",");
          return forwards[0].trim();
      }
docs: This method returns a host name of a web server if this container is fronted by one, such that
  it sets a header <code>X-Forwarded-Host</code> on the request and forwards it to the Java container.
  If such header is not present, than the {@link #host()} method is used.
  
  @return host name of web server if <code>X-Forwarded-Host</code> header is found, otherwise local host name.