一、Java獲取服務器IP（轉自：https://www.cnblogs.com/george93/p/6306579.html）

//方法一，也是最簡單的一種。
    String SERVER_IP = InetAddress.getLocalHost().getHostAdress().toString();
//方法二：
/**
     * 獲取服務器IP地址
     * @return
     */
    @SuppressWarnings("unchecked")
    public static String  getServerIp(){
        String SERVER_IP 
 
= null;
        try {
            Enumeration netInterfaces = NetworkInterface.getNetworkInterfaces();
            InetAddress ip = null;
            while (netInterfaces.hasMoreElements()) {
                NetworkInterface ni = (NetworkInterface) netInterfaces.nextElement();
                ip = (InetAddress) ni.getInetAddresses().nextElement();
                SERVER_IP 
 
= ip.getHostAddress();
                if (!ip.isSiteLocalAddress() && !ip.isLoopbackAddress()
                        && ip.getHostAddress().indexOf(":") == -1) {
                    SERVER_IP = ip.getHostAddress();
                    break;
                } else {
                    ip 
 
= null;
                }
            }
        } catch (SocketException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    
        return SERVER_IP;
    }
}

二、Java獲取客戶端IP（轉自：http://www.cnblogs.com/ITtangtang/p/3927768.html）

　　其核心思想是通過HTTP的Servlet來獲取；

//第一種
/**
      * 從Request對象中獲得客戶端IP，處理了HTTP代理服務器和Nginx的反向代理截取了ip
      * @param request
      * @return ip
      */
    public static String getLocalIp(HttpServletRequest request) {
        String remoteAddr = request.getRemoteAddr();
        String forwarded = request.getHeader("X-Forwarded-For");
        String realIp = request.getHeader("X-Real-IP");

        String ip = null;
        if (realIp == null) {
            if (forwarded == null) {
                ip = remoteAddr;
            } else {
                ip = remoteAddr + "/" + forwarded.split(",")[0];
            }
        } else {
            if (realIp.equals(forwarded)) {
                ip = realIp;
            } else {
                if(forwarded != null){
                    forwarded = forwarded.split(",")[0];
                }
                ip = realIp + "/" + forwarded;
            }
        }
        return ip;
    }

//第二種
public static String getIp(HttpServletRequest request) {
        String remoteAddr = request.getRemoteAddr();
        String forwarded = request.getHeader("X-Forwarded-For");
        String realIp = request.getHeader("X-Real-IP");

        String ip = null;
        if (realIp == null) {
            if (forwarded == null) {
                ip = remoteAddr;
            } else {
                ip = remoteAddr + "/" + forwarded;
            }
        } else {
            if (realIp.equals(forwarded)) {
                ip = realIp;
            } else {
                ip = realIp + "/" + forwarded.replaceAll(", " + realIp, "");
            }
        }
        return ip;
    }

//第三種，也是最清晰合理的一種
public static String getIp2(HttpServletRequest request) {
           String ip = request.getHeader("X-Forwarded-For");
           if(StringUtils.isNotEmpty(ip) && !"unKnown".equalsIgnoreCase(ip)){
               //多次反向代理後會有多個ip值，第一個ip才是真實ip
               int index = ip.indexOf(",");
               if(index != -1){
                   return ip.substring(0,index);
               }else{
                   return ip;
               }
           }
           ip = request.getHeader("X-Real-IP");
           if(StringUtils.isNotEmpty(ip) && !"unKnown".equalsIgnoreCase(ip)){
               return ip;
           }
           return request.getRemoteAddr();
       }

java獲取客戶端IP和服務器IP