gistfile1.java

public final class HTTPUtils {

   private static final String HEADER_X_FORWARDED_FOR = "X-FORWARDED-FOR";

   public static String remoteAddr(HttpServletRequest request) {

       String remoteAddr = request.getRemoteAddr();
       String x;

       if ((x = request.getHeader(HEADER_X_FORWARDED_FOR)) != null) {

           remoteAddr = x;
           int idx = remoteAddr.indexOf(',');
           if (idx > -1) {
               remoteAddr = remoteAddr.substring(0, idx);
           }
       }
       return remoteAddr;
   }
}

//Example borrowed from Johann Burkard blog