Log TraceNo for each request in web application using Log4j

I have a class named TraceNoGenerator that works like a Sequence in an Oracle Database; I want to use this class to assign a trace number for each request that comes to my web application to log in a log file. When my application received an error, this trace number will display on a web page so that I can easily find the bug开发者_如何学Go using this trace number in the log file.

How can I do this in Log4j?