Java获取客户端真实IP地址详解编程语言

import javax.servlet.http.HttpServletRequest;   
   
/**  
 * 获取对象的IP地址等信息 */   
public class IPUtil {   
   
    /**  
     * 获取用户真实IP地址，不使用request.getRemoteAddr();的原因是有可能用户使用了代理软件方式避免真实IP地址,  
     * 可是，如果通过了多级反向代理的话，X-Forwarded-For的值并不止一个，而是一串IP值，究竟哪个才是真正的用户端的真实IP呢？  
     * 答案是取X-Forwarded-For中第一个非unknown的有效IP字符串。  
     * 如：X-Forwarded-For：192.168.1.110, 192.168.1.120, 192.168.1.130,  
     * 192.168.1.100  
     * 用户真实IP为： 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;   
    }   
       
}