private String getHttpMethodFrom(HttpServletRequest httpRequest) {
        String method = httpRequest.getHeader(HTTP_METHOD_OVERRIDE_HEADER);

        if (method == null) {
            method = httpRequest.getMethod();
        }
        return method;
    }
Constructor

@param routeMatcher      The route matcher
@param staticFiles       The static files configuration object
@param externalContainer Tells the filter that Spark is run in an external web container.
                         If true, chain.doFilter will be invoked if request is not consumed by Spark.
@param hasOtherHandlers  If true, do nothing if request is not consumed by Spark in order to let others handlers process the request.
src/main/java/spark/http/matching/MatcherFilter.java