// custom http headers last so they can be overridden
StringToStringsMap headers = httpRequest.getRequestHeaders();
// clear headers specified in GUI, and re-add them, with property expansion
for (String headerName : headers.keySet()) {
String expandedHeaderName = PropertyExpander.expandProperties(submitContext, headerName);
httpMethod.removeHeaders(expandedHeaderName);
for (String headerValue : headers.get(headerName)) {
headerValue = PropertyExpander.expandProperties(submitContext, headerValue);
httpMethod.addHeader(expandedHeaderName, headerValue);