Spring 框架中获取客户端真实 IP

在 Spring Web 项目中，如果服务经过 Nginx、网关或多层代理，直接读取 request.getRemoteAddr() 往往拿不到真正的客户端 IP。一般需要结合 HttpServletRequest 中的多个请求头来判断。

题外话：前端如果只是临时查看公网 IP，也可以调用现成接口，例如搜狐提供的 https://pv.sohu.com/cityjson?ie=utf-8。

下面是一段常见的 Java 获取客户端 IP 的代码：

/** 
 * @Description: 获取客户端IP地址   
 */  
private 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();   
        if(ip.equals("127.0.0.1")){     
            //根据网卡取本机配置的IP     
            InetAddress inet=null;     
            try {     
                inet = InetAddress.getLocalHost();     
            } catch (Exception e) {     
                e.printStackTrace();     
            }     
            ip= inet.getHostAddress();     
        }  
    }   
    // 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(ip != null && ip.length() > 15){    
        if(ip.indexOf(",")>0){     
            ip = ip.substring(0,ip.indexOf(","));     
        }     
    }     
    return ip;   
}

注意，此处获取的第一个HTTP header字段x-forwarded-for，可能被伪造，具体参见这篇文章：HTTP 请求头中的 X-Forwarded-For，X-Real-IP

对上述代码做改造，即可得到如下代码：

/** 
 * @Description: 获取客户端IP地址   
 */  
private String getIpAddr(HttpServletRequest request) {   
    String ip = request.getHeader("x-Real-IP");   
    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();   
        if(ip.equals("127.0.0.1")){     
            //根据网卡取本机配置的IP     
            InetAddress inet=null;     
            try {     
                inet = InetAddress.getLocalHost();     
            } catch (Exception e) {     
                e.printStackTrace();     
            }     
            ip= inet.getHostAddress();     
        }  
    }   
    // 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(ip != null && ip.length() > 15){    
        if(ip.indexOf(",")>0){     
            ip = ip.substring(0,ip.indexOf(","));     
        }     
    }     
    return ip;   
}

参考资料

• HTTP 请求头中的 X-Forwarded-For，X-Real-IP
• spring框架中获取访问端的ip地址