Spring:获取真实IP地址

使用Nginx等反向代理软件， 则不能通过request.getRemoteAddr()获取IP地址

如果使用了多级反向代理的话，X-Forwarded-For的值并不止一个，而是一串IP地址，X-Forwarded-For中第一个非unknown的有效IP字符串，则为真实IP地址

public class IpUtil {
    private final static String UNKNOWN = "unknown";
    private final static int MAX_LENGTH = 15;


    public static String getIpAddr() {
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
        String ip = null;
        try {
            ip = request.getHeader("x-forwarded-for");
            if (StrUtil.isEmpty(ip) || UNKNOWN.equalsIgnoreCase(ip)) {
                ip = request.getHeader("Proxy-Client-IP");
            }
            if (StrUtil.isEmpty(ip) || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {
                ip = request.getHeader("WL-Proxy-Client-IP");
            }
            if (StrUtil.isEmpty(ip) || UNKNOWN.equalsIgnoreCase(ip)) {
                ip = request.getHeader("HTTP_CLIENT_IP");
            }
            if (StrUtil.isEmpty(ip) || UNKNOWN.equalsIgnoreCase(ip)) {
                ip = request.getHeader("HTTP_X_FORWARDED_FOR");
            }
            if (StrUtil.isEmpty(ip) || UNKNOWN.equalsIgnoreCase(ip)) {
                ip = request.getRemoteAddr();
            }
        } catch (Exception e) {
            log.error("IPUtils ERROR ", e);
        }
        // 使用代理，则获取第一个IP地址
        if (!StrUtil.isEmpty(ip) && ip.length() > MAX_LENGTH) {
            if (ip.indexOf(StrUtil.COMMA) > 0) {
                ip = ip.substring(0, ip.indexOf(StrUtil.COMMA));
            }
        }
        return ip;
    }
}