为了从 jakarta.servlet.http.HttpServletRequest 获取客户端的IP地址，你可以编写一个辅助方法来检查多个HTTP头信息以确定客户端的真实IP地址。考虑到可能存在的代理服务器或负载均衡器，直接使用 request.getRemoteAddr() 可能无法获取到真实的客户端IP。

下面是一个示例方法，用于从 HttpServletRequest 对象中提取客户端的IP地址：

import jakarta.servlet.http.HttpServletRequest;

public class IpAddressUtil {

    public static String getClientIp(HttpServletRequest request) {
        // Check for headers commonly used by proxies to forward the original IP address.
        String ip = request.getHeader("X-Forwarded-For");
        if (ip == null || ip.isEmpty() || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("Proxy-Client-IP");
        }
        if (ip == null || ip.isEmpty() || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("WL-Proxy-Client-IP");
        }
        if (ip == null || ip.isEmpty() || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_CLIENT_IP");
        }
        if (ip == null || ip.isEmpty() || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_X_FORWARDED_FOR");
        }
        if (ip == null || ip.isEmpty() || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getRemoteAddr();
        }

        // If the IP address is still unknown, return null or a default value.
        if ("0:0:0:0:0:0:0:1".equals(ip) || "127.0.0.1".equals(ip)) {
            // Localhost address, you might want to handle this specially.
            return "localhost";
        }

        // For cases where there are multiple IPs in the X-Forwarded-For header,
        // take the first one as the client's IP address.
        if (ip != null && ip.contains(",")) {
            ip = ip.split(",")[0].trim();
        }

        return ip;
    }
}

这段代码首先尝试通过常见的HTTP头部字段（如 X-Forwarded-For）获取IP地址，这些字段通常由代理服务器设置。如果这些头部不存在或包含未知值，则最终回退到使用 getRemoteAddr() 方法。

请注意，由于HTTP头部可以被客户端伪造，因此在安全敏感的应用中应该谨慎处理，并且可能需要对来自代理或负载均衡器的请求进行额外验证。如果你使用的是像Hutool这样的库，它们通常已经提供了类似的实用方法来简化这个过程。