java 从HttpServletRequest中获取ip地址

可以通过以下代码从HttpServletRequest中获取IP地址：

String 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.getHeader("HTTP_CLIENT_IP");
}
if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
    ipAddress = request.getHeader("HTTP_X_FORWARDED_FOR");
}
if (ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {
    ipAddress = request.getRemoteAddr();
}

这段代码从多个头部获取IP地址，包括 `X-Forwarded-For`、`Proxy-Client-IP`、`WL-Proxy-Client-IP`、`HTTP_CLIENT_IP`、`HTTP_X_FORWARDED_FOR`，如果这些头部都没有获取到IP地址，则使用 `getRemoteAddr()` 方法获取IP地址。