获得客户端的真实IP

public class IPUtil {
    public static String getIpAddr(HttpServletRequest request) {
        String ip = request.getHeader("X-Real-IP");
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
         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();
        }
        //防止多级代理时返回过个ip。
        if(ip != null && ip.indexOf(",") != -1){
            ip= ip.substring(0,ip.indexOf(","));
        }
        return ip;
    }
}