获取访问客户端ip

private boolean isValidIp(String ip){
         return !(StringUtils.isEmpty(ip) || "unknown".equalsIgnoreCase(ip));
     }
 
     private String getIp(HttpServletRequest request){
         //一些代理
           String ip = request.getHeader("X-Forwarded-For");  
         if (isValidIp(ip)) { 
             return ip;
         }
         //一般是经过apache http服务器的请求才会有，用apache http做代理时一般会加上Proxy-Client-IP请求头
         ip = request.getHeader("Proxy-Client-IP");          
         if (isValidIp(ip)) { 
             return ip;
         }
         //WL-Proxy-Client-IP是apache的weblogic插件加上的头
         ip = request.getHeader("WL-Proxy-Client-IP");          
         if (isValidIp(ip)) {   
             return ip;
         }
         //有些代理服务器会加上此请求头
         ip = request.getHeader("HTTP_CLIENT_IP");        
         if (isValidIp(ip)) {  
             return ip;
         }
         ip = request.getHeader("HTTP_X_FORWARDED_FOR");         
         if (isValidIp(ip)) {
             return ip;
         }
         //nginx代理一般会加上此请求头
         ip = request.getHeader("X-Real-IP"); 
         if (isValidIp(ip)) {
             return ip;
         }        
         //这个ip虽然不一定是来自客户端的ip，但是不能被伪造，上面其他方式获取的ip却有可能被伪造！！！
         ip = request.getRemoteAddr();    
         return ip;
     }