In JAVA, the server obtains the real IP address of the client

转自：http://www.cnblogs.com/xjh5201314/p/6591174.html
1 public static String getIpAddress(HttpServletRequest request){
2        
3         String ipAddress = request.getHeader("x-forwarded-for");
4        
5         if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
6             ipAddress = request.getHeader("Proxy-Client-IP");
7         }
8         if (ipAddress == null || ipAddress.length() == 0 || "unknow".equalsIgnoreCase(ipAddress)) {
9             ipAddress = request.getHeader("WL-Proxy-Client-IP");
10         }
11         if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
12 ipAddress = request.getRemoteAddr();
13            
14 if(ipAddress.equals("127.0.0.1") || ipAddress.equals("0:0:0:0:0:0:0:1")){
15 //Acquire the IP address of the local machine according to the network card
16 InetAddress inetAddress = null;
17 try {
18 inetAddress = InetAddress.getLocalHost();
19 } catch (UnknownHostException e) {
20 e.printStackTrace();
21 }
22 ipAddress = inetAddress .getHostAddress();
23 }
24 }
25        
26 //For the case of multiple proxies, the first IP is the real IP address of the client, and multiple IPs are divided according to ','
27 if(null != ipAddress && ipAddress.length() > 15){
28 //"***.***.***.***".length() = 15
29 if(ipAddress.indexOf( ",") > 0){
30 ipAddress = ipAddress.substring(0, ipAddress.indexOf(","));
31 }
32 }
33        
34 return ipAddress;
35 }
The if() statement at the bottom of the method is to prevent Using the tomcat server, when testing locally, the ip address obtained is 127.0.0.1.
Quoted from: Under the multi-level reverse proxy, Java obtains the real IP address of the requesting client and integrates multiple methods