Servlet Gets the client IP address

In the JSP, the method to obtain the IP address of the client is: Request.getremoteaddr (), which is valid in most cases. However, the real IP address of the client cannot be obtained through the reverse proxy software such as Apache,squid. If the reverse proxy software is used, the IP address obtained with the REQUEST.GETREMOTEADDR () method is: 127.0.0.1 or 192.168.1.110, not the real IP of the client.

After the agent, due to the addition of the middle tier between the client and the service, so the server can not directly get the client's IP, the server-side application can not directly forward the requested address to the client. However, the x-forwarded-for information is added to the HTTP header information of the forwarding request. Used to track the original client IP address and the server address of the original client request. When we visit index.jsp/, it is not that our browser actually accesses the index.jsp file on the server, but first the proxy server to access the index.jsp, the proxy server will return the results of the access to our browser, Because it is the proxy server to access the index.jsp, the IP index.jsp in the Request.getremoteaddr () method is actually the address of the proxy server, not the IP address of the client.

So we can get the real IP address of the client method one:

Public String Getremortip (HttpServletRequest request) {

if (Request.getheader ("x-forwarded-for") = = null) {

return request.getremoteaddr ();

}

Return Request.getheader ("X-forwarded-for");

}

To obtain the client's real IP address method two:

Public String getipaddr (HttpServletRequest request) {

String IP = request.getheader ("X-forwarded-for");

if (IP = = NULL | | ip.length () = = 0 | | "Unknown". Equalsignorecase (IP)) {

ip = Request.getheader ("Proxy-client-ip");

}

if (IP = = NULL | | ip.length () = = 0 | | "Unknown". Equalsignorecase (IP)) {

ip = Request.getheader ("Wl-proxy-client-ip");

}

if (IP = = NULL | | ip.length () = = 0 | | "Unknown". Equalsignorecase (IP)) {

ip = request.getremoteaddr ();

}

return IP;

}

However, if through the multi-level reverse proxy, x-forwarded-for value and more than one, but a string of IP values, exactly which is the real client IP?

The answer is to take the first non-unknown valid IP string in x-forwarded-for. Such as:

x-forwarded-for:192.168.1.110, 192.168.1.120, 192.168.1.130, 192.168.1.100

User Real IP: 192.168.1.110

Servlet gets client IP address