I have started being interested in browser fingerprints. As far as I understand: "The header order of each browser is fixed and cannot be changed in the browser settings." So,... to a start, I want to read the browser headers in the order in which they are sent by the browser.
I have tried with plain Java's "request.getHeaderNames()", but this does not provide the correct order. (see my more restricted question here)
So my question is: How do I read browser header sequence from a Tomcat web server?
The servlet API is independent of http-header order, and tomcat - as you have discovered - parses the headers and stores them in a map with no particular order.
If you're interested in the raw content of the request, you'd have to replace tomcat's parsing code - e.g. find where the headers are parsed and change that behavior. Once tomcat has done its parsing, I suspect that you can't rewind the input stream and read the raw headers again. You'd then need to either store them in a map that retains the order of headers, or save specific request attributes with the raw data, that your application can later work with.
In any case: If you use Tomcat for this task, you'd have to dig deep into its implementation.