Java获取用户访问IP地址

Java中获取访问用户的真实IP地址，可通过HttpServletRequest的getRemoteAddr方法，如果用户使用了多级代理，可能就拿不到；
此时可通过请求头中的X-Forwarded-For获取，X-Forwarded-For是一串IP值，取X-Forwarded-For中第一个非unknown的有效IP字符串。

获取客户端IP地址工具类IpUtils：

import javax.servlet.http.HttpServletRequest;
import org.apache.commons.lang.StringUtils;
import javax.servlet.http.HttpServletRequest;

public class IpUtils {

    private static final String LOCAL_HOST = "127.0.0.1";
    private static final String X_FORWARDED_FOR = "x-forwarded-for";
    private static final String UNKNOWN = "unknown";

    /**
     * 获取用户ip地址
     *
     * @return
     */
    public static String getIpAddress(HttpServletRequest request) {
        if (request == null) {
                return "";
            }
            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.getHeader("X-Real-IP");
            }
            // 如果没有代理，则获取真实ip
            if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {
                ip = request.getRemoteAddr();
            }
            // 获取到多个ip时取第一个作为客户端真实ip
            if (StringUtils.isNotBlank(ip) && ip.contains(",") && ip.trim().length() > 1) {
                ip = ip.split(",")[0];
            }
            if ("0:0:0:0:0:0:0:1".equals(ip)) {
                ip = LOCAL_HOST;
            }
            return ip;
        }
    }

}

如果使用Nginx做反向代理，则还需要添加如下配置：

location / {
    proxy_pass http://127.0.0.1:8899;
    # 添加如下4行
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header REMOTE-HOST $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}