presto-main/src/main/java/io/prestosql/server/HttpRequestSessionContext.java/HttpRequestSessionContext/parseProperty
class HttpRequestSessionContext:    private static Map<String, String> parseProperty(HttpServletRequest servletRequest, String headerName)
    {
        Map<String, String> properties = new HashMap<>();
        for (String header : splitSessionHeader(servletRequest.getHeaders(headerName))) {
            List<String> nameValue = Splitter.on('=').trimResults().splitToList(header);
            assertRequest(nameValue.size() == 2, "Invalid %s header", headerName);
            try {
                properties.put(nameValue.get(0), urlDecode(nameValue.get(1)));
            }
            catch (IllegalArgumentException e) {
                throw badRequest(format("Invalid %s header: %s", headerName, e));
            }
        }
        return properties;
    }