java web 通過request獲取客戶端IP

 /** 
  * 獲取使用者真實IP地址，不使用request.getRemoteAddr();的原因是有可能使用者使用了代理軟體方式避免真實IP地址, 
  * 
  * 可是，如果通過了多級反向代理的話，X-Forwarded-For的值並不止一個，而是一串IP值，究竟哪個才是真正的使用者端的真實IP呢？ 
  * 答案是取X-Forwarded-For中第一個非unknown的有效IP字串。 
  * 
  * 如：X-Forwarded-For：192.168.1.110, 192.168.1.120, 192.168.1.130, 
  * 192.168.1.100 
  * 
  * 使用者真實IP為： 192.168.1.110 
  * 
  * @param request 
  * @return 
  */ 
 public static String getIpAddress(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(); 
   } 
   return ip; 
 }