Java Get User IP

How does Java get the client IP?
Here are a few of the methods I've summed up:

/** * Get client IP address (can penetrate proxy) * * @param request * @return  * *     Public StaticStringgetremoteaddr(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.getheader ("Http_client_ip"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("Http_x_forwarded_for"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = request.getremoteaddr (); }returnip }Private Static FinalString[] Headers_to_try = {"X-forwarded-for","Proxy-client-ip","Wl-proxy-client-ip","Http_x_forwarded_for","http_x_forwarded","Http_x_cluster_client_ip","Http_client_ip","Http_forwarded_for","http_forwarded","Http_via","REMOTE_ADDR","X-real-ip"};/*** * Get client IP address (can penetrate proxy) * @param request * @return  * *     Public StaticStringgetclientipaddress(HttpServletRequest request) { for(String header:headers_to_try) {String IP = request.getheader (header);if(IP! =NULL&& ip.length ()! =0&&!"Unknown". Equalsignorecase (IP)) {returnip }        }returnRequest.getremoteaddr (); }/*** * Get client IP address (can penetrate proxy) * @param request * @return  * *     Public StaticStringgetclientipaddr(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.getheader ("Http_x_forwarded_for"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("http_x_forwarded"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("Http_x_cluster_client_ip"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("Http_client_ip"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("Http_forwarded_for"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("http_forwarded"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("Http_via"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = Request.getheader ("REMOTE_ADDR"); }if(IP = =NULL|| Ip.length () = =0||"Unknown". Equalsignorecase (IP)) {IP = request.getremoteaddr (); }returnip } Public StaticStringgetipaddr(HttpServletRequest request) {String IP = request.getheader ("X-real-ip");if(NULL! = IP &&!"". Equals (Ip.trim ()) &&!"Unknown". Equalsignorecase (IP)) {returnip } IP = Request.getheader ("X-forwarded-for");if(NULL! = IP &&!"". Equals (Ip.trim ()) &&!"Unknown". Equalsignorecase (IP)) {//Get first IP from proxy IP            intindex = Ip.indexof (', ');if(Index! =-1) {returnIp.substring (0, index); }Else{returnip }        }returnRequest.getremoteaddr (); }

I am using the Spring MVC Framework, which tests the controller code as follows:

Packagecom. Web. Controller;Import Java. Util. HashMap;Import Java. Util. Map;Import Javax. servlet. HTTP. HttpServletRequest;import org. Springframework. Stereotype. Controller;import org. Springframework. Web. Bind. Annotation. Requestmapping;import org. Springframework. Web. Bind. Annotation. Responsebody;Importcom. Common. Util. Systemhwutil;Importcom. Common. Util. Webservletutil;Importcom. String. Widgets. Util. Valuewidget;Importcom. Util. Jsonputil;/*** * For testing cross-domain * @author huangweii * May 29, 2015 * *@Controller @requestmapping ("/cors") public class Corscontroller {@ResponseBody @RequestMapping (value ="/simple", Produces=systemhwutil. RESPONSE_CONTENTTYPE_JSON_UTF) public String corsjsonsimple (HttpServletRequest request,string callback) {string content;Map map=new HashMap ();Map. Put("username","Good");Map. Put("Age"," the");Map. Put("Address","Beijing");Content=jsonputil. Getjsonp(Map, callback);System. out. println("GETIPADDR:"+webservletutil. Getipaddr(request));System. out. println("GETREMOTEADDR:"+webservletutil. Getremoteaddr(request));System. out. println("GETCLIENTIPADDR:"+webservletutil. Getclientipaddr(request));System. out. println("getclientipaddress:"+webservletutil. Getclientipaddress(request));return content;}}

Test results:

Java Get User IP