java - Getting IP address of client

Question

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Answer 1

As @martin and this answer explained, it is complicated. There is no bullet-proof way of getting the client's ip address.

The best that you can do is to try to parse "X-Forwarded-For" and rely on request.getRemoteAddr();

public static String getClientIpAddress(HttpServletRequest request) {
    String xForwardedForHeader = request.getHeader("X-Forwarded-For");
    if (xForwardedForHeader == null) {
        return request.getRemoteAddr();
    } else {
        // As of https://en.wikipedia.org/wiki/X-Forwarded-For
        // The general format of the field is: X-Forwarded-For: client, proxy1, proxy2 ...
        // we only want the client
        return new StringTokenizer(xForwardedForHeader, ",").nextToken().trim();
    }
}