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当处理来自客户端的请求时，尤其是在存在代理服务器的情况下，可能需要考虑多种HTTP请求头，以尽可能准确地获取用户的真实IP地址。以下是考虑了X-Forwarded-For、Proxy-Client-IP、WL-Proxy-Client-IP、HTTP_CLIENT_IP、HTTP_X_FORWARDED_FOR的请求头的代码：

import javax.servlet.http.HttpServletRequest;public class NetworkUtil {public static String getRealIpAddress(HttpServletRequest request) {String[] headerNames = {"X-Forwarded-For","Proxy-Client-IP","WL-Proxy-Client-IP","HTTP_CLIENT_IP","HTTP_X_FORWARDED_FOR"};String ipAddress = null;for (String header : headerNames) {ipAddress = request.getHeader(header);if (ipAddress != null && !ipAddress.isEmpty() && !"unknown".equalsIgnoreCase(ipAddress)) {break;}}if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getRemoteAddr();}// 其中X-Forwarded-For可能含有多个IP地址，第一个非unknown的有效IP字符串即为用户的真实IPif (ipAddress != null && ipAddress.length() > 15) { // "xxx.xxx.xxx.xxx".length() = 15if (ipAddress.indexOf(",") > 0) {ipAddress = ipAddress.substring(0, ipAddress.indexOf(",")).trim();}}return ipAddress;}
}