servlet request getHeader("x-forwarded-for") 获取真实IP

在JSP里，获取客户端的IP地址的方法是：request.getRemoteAddr()，这种方法在大部分情况下都是有效的。但是在通过了 Apache，Nagix等反向代理软件就不能获取到客户端的真实IP地址了。如果使用了反向代理软件，用 request.getRemoteAddr()方法获取的IP地址是：127.0.0.1或 192.168.1.110，而并不是客户端的真实IP。

      经过代理以后，由于在客户端和服务之间增加了中间层，因此服务器无法直接拿到客户端的 IP，服务器端应用也无法直接通过转发请求的地址返回给客户端。但是在转发请求的HTTP头信息中，增加了X-FORWARDED-FOR信息。用以跟踪原有的客户端 IP地址和原来客户端请求的服务器地址。

      举例来说，当我们访问口碑网首页hangzhou.jsp时，其实并不是我们浏览器真正访问到了服务器上的hangzhou.jsp 文件，而是先由代理服务器Nagix去访问hagnzhou.jsp ，代理服务器再将访问到的结果返回给我们的浏览器，因为是代理服务器去访问hangzhou.jsp的，所以hangzhou.jsp中通过 request.getRemoteAddr()的方法获取的IP实际上是代理服务器的地址，并不是客户端的IP地址。

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获得客户端真实IP地址的方法一：

public String getRemortIP(HttpServletRequest request) {
　　      if (request.getHeader("x-forwarded-for") == null) {
　　            return request.getRemoteAddr();
　　      }
　　      return request.getHeader("x-forwarded-for");
　　}

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获得客户端真实IP地址的方法二

public String getIpAddr(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.getRemoteAddr();
　　      }
　　      return ip;
　　}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

 /**
     * 获取请求主机IP地址,如果通过代理进来，则透过防火墙获取真实IP地址;
     *
     * @param request
     * @return
     * @throws IOException
     */
    public final static String getIpAddr(HttpServletRequest request){
        // 获取请求主机IP地址,如果通过代理进来，则透过防火墙获取真实IP地址

        String ip = request.getHeader("X-Forwarded-For");
        if (log.isInfoEnabled()) {
            log.info("getIpAddress(HttpServletRequest) - X-Forwarded-For - String ip=" + ip);
        }
        try{
            if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                    ip = request.getHeader("Proxy-Client-IP");
                    if (log.isInfoEnabled()) {
                        log.info("getIpAddress(HttpServletRequest) - Proxy-Client-IP - String ip=" + ip);
                    }
                }
                if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                    ip = request.getHeader("WL-Proxy-Client-IP");
                    if (log.isInfoEnabled()) {
                        log.info("getIpAddress(HttpServletRequest) - WL-Proxy-Client-IP - String ip=" + ip);
                    }
                }
                if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                    ip = request.getHeader("HTTP_CLIENT_IP");
                    if (log.isInfoEnabled()) {
                        log.info("getIpAddress(HttpServletRequest) - HTTP_CLIENT_IP - String ip=" + ip);
                    }
                }
                if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                    ip = request.getHeader("HTTP_X_FORWARDED_FOR");
                    if (log.isInfoEnabled()) {
                        log.info("getIpAddress(HttpServletRequest) - HTTP_X_FORWARDED_FOR - String ip=" + ip);
                    }
                }
                if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
                    ip = request.getRemoteAddr();
                    if (log.isInfoEnabled()) {
                        log.info("getIpAddress(HttpServletRequest) - getRemoteAddr - String ip=" + ip);
                    }
                }
            } else if (ip.length() > 15) {
                String[] ips = ip.split(",");
                for (int index = 0; index < ips.length; index++) {
                    String strIp = (String) ips[index];
                    if (!("unknown".equalsIgnoreCase(strIp))) {
                        ip = strIp;
                        break;
                    }
                }
            }
        }catch (Exception e){
            log.info("get ip error!");
        }

        return ip;
    }