检查正则表达式是否与可选组匹配

Question

I'm trying to match an HTTP request line and to fetch the requested item. I have the following regular expression:

Pattern regex = Pattern.compile("GET /(\\w+\\.\\w+)? HTTP/1.1");

If you check it, you will notice an optional group (\\\\w+\\\\.\\\\w+)? . When I send a file, like for example GET /index.html HTTP/1.1 it works correctly and matcher.groupCount() returns 1 . The problem is when I send something like GET / HTTP/1.1 . I don't know how to check if the group has been matched, since matcher.groupCount() returns 1 as well. I suspect that the groupCount() function returns the number of groups in the regex regardless of their existence in the parsed String.

Thanks

Answer 1

You don't need to use optional group here actually. This regex will work better for you:

Pattern regex = Pattern.compile("GET (/\\S+) HTTP/1\.1");

ie match & capture everything from first / until you hit a space as the REQUEST URI .

Remember a web request can contain query parameters also with ? , & etc and \\\\w+\\\\.\\\\w+ is not a good regex to match them all.