java 获取请求客户端的真实IP地址

转载自：http://leiyongping88.iteye.com/blog/1545930

用request.getRemoteAddr();
方法获取的IP地址是:127.0.0.1或192.168.0.66,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。

public static 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;
}

像移动网关一样，iisforward这个ISAPI过滤器也会对request对象进行再包装，附加一些WLS要用的头信息。这种情况下，直接用request.getRemoteAddr()是无法取到真正的客户IP的。
实际的iisforward附加头如下：
WL-Proxy-Client-IP=215.4.1.29
Proxy-Client-IP=215.4.1.29
X-Forwarded-For=215.4.1.29
WL-Proxy-Client-Keysize=
WL-Proxy-Client-Secretkeysize=
X-WebLogic-Request-ClusterInfo=true
X-WebLogic-KeepAliveSecs=30
X-WebLogic-Force-JVMID=-527489098
WL-Proxy-SSL=false

public static String getIpAddr(HttpServletRequest request) {
    String ipAddress = null;
    ipAddress = request.getHeader("x-forwarded-for");
    if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
        ipAddress = request.getHeader("Proxy-Client-IP");
    }
    if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
        ipAddress = request.getHeader("WL-Proxy-Client-IP");
     }
    if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
        ipAddress = request.getRemoteAddr();
        if(ipAddress.equals("127.0.0.1")){
            //根据网卡取本机配置的IP
            InetAddress inet=null;
            try {
                inet = InetAddress.getLocalHost();
            } catch (UnknownHostException e) {
                e.printStackTrace();
            }
            ipAddress= inet.getHostAddress();
        }

    }

    //对于通过多个代理的情况，第一个IP为客户端真实IP,多个IP按照','分割
    if(ipAddress!=null && ipAddress.length()>15){ //"***.***.***.***".length() = 15
        if(ipAddress.indexOf(",")>0){
            ipAddress = ipAddress.substring(0,ipAddress.indexOf(","));
        }
    }
    return ipAddress;
}