Java 獲取客戶端信息：User-Agent 解析、作業系統、瀏覽器、IP 與 Servlet 核心屬性

Servlet 請求對象攜帶豐富的客戶端環境信息。本文系統匯總 HttpServletRequest 核心屬性獲取方法、User-Agent 解析策略、真實 IP 提取、跨語言對比 (ASP.NET/PHP/JS) 及生產環境注意事項。

核心屬性一鍵獲取工具類

public final class ClientInfoExtractor {
    public static ClientInfo extract(HttpServletRequest request) {
        ClientInfo info = new ClientInfo();
        
        // 1. User-Agent 原始字符串
        String ua = request.getHeader("User-Agent");
        info.setUserAgent(ua);
        
        // 2. 解析瀏覽器與作業系統 (簡易版，生產建議用 ua-parser)
        if (ua != null) {
            info.setBrowser(parseBrowser(ua));
            info.setOs(parseOs(ua));
        }
        
        // 3. Servlet 標準屬性
        info.setMethod(request.getMethod());
        info.setRequestURI(request.getRequestURI());
        info.setServletPath(request.getServletPath());
        info.setServerName(request.getServerName());
        info.setServerPort(request.getServerPort());
        info.setRemoteAddr(request.getRemoteAddr());      // 直接客戶端 IP (可能是代理)
        info.setRemoteHost(request.getRemoteHost());      // 客戶端主機名
        info.setProtocol(request.getProtocol());          // HTTP/1.1
        info.setScheme(request.getScheme());              // http/https
        info.setQueryString(request.getQueryString());
        info.setAuthType(request.getAuthType());
        info.setContentLength(request.getContentLengthLong());
        info.setContentType(request.getContentType());
        info.setCharacterEncoding(request.getCharacterEncoding());
        info.setSessionId(request.getRequestedSessionId());
        
        // 4. 所有 Header (調試用)
        Map headers = new HashMap<>();
        Enumeration names = request.getHeaderNames();
        while (names.hasMoreElements()) {
            String name = names.nextElement();
            headers.put(name, request.getHeader(name));
        }
        info.setHeaders(headers);
        
        return info;
    }
    
    // 簡易解析示例 (生產請用 ua-parser-js / Yauaa)
    private static String parseBrowser(String ua) {
        if (ua.contains("Edg/")) return "Edge";
        if (ua.contains("Chrome/")) return "Chrome";
        if (ua.contains("Firefox/")) return "Firefox";
        if (ua.contains("Safari/")) return "Safari";
        if (ua.contains("MSIE") || ua.contains("Trident")) return "IE";
        return "Unknown";
    }
    
    private static String parseOs(String ua) {
        if (ua.contains("Windows NT 10.0")) return "Windows 10/11";
        if (ua.contains("Windows NT 6.3")) return "Windows 8.1";
        if (ua.contains("Windows NT 6.1")) return "Windows 7";
        if (ua.contains("Mac OS X")) return "macOS";
        if (ua.contains("Linux")) return "Linux";
        if (ua.contains("Android")) return "Android";
        if (ua.contains("iPhone") || ua.contains("iPad")) return "iOS";
        return "Unknown";
    }
}

Servlet 核心屬性完整速查表

常見 Header 速查

跨語言獲取 User-Agent 對比

生產級 User-Agent 解析：引入專業庫

手寫正則不可維護，推薦：

• Java：Yauaa (Yet Another User Agent Analyzer) — 準確率高、更新快、支持設備類型/品牌/型號。
• JavaScript：ua-parser-js — 輕量、瀏覽器/Node 通用。
• Python：ua-parser — 官方庫。
• Go：useragent。

Yauaa 快速上手

    nl.basjes.parse.useragent
    yauaa
    7.3.0


// 使用
UserAgentAnalyzer analyzer = UserAgentAnalyzer.newBuilder().build();
UserAgent agent = analyzer.parse(request.getHeader("User-Agent"));
String browser = agent.getValue(UserAgent.BROWSER_NAME);      // Chrome
String version = agent.getValue(UserAgent.BROWSER_VERSION);   // 119.0.0.0
String os = agent.getValue(UserAgent.OPERATING_SYSTEM_NAME);  // Windows 10
String device = agent.getValue(UserAgent.DEVICE_CLASS);       // Desktop

真實 IP 提取最佳實踐 (重申)

public static String getRealIp(HttpServletRequest request) {
    String ip = request.getHeader("X-Forwarded-For");
    if (isValidIp(ip)) return ip.split(",")[0].trim();
    
    ip = request.getHeader("X-Real-IP");
    if (isValidIp(ip)) return ip;
    
    return request.getRemoteAddr();
}

private static boolean isValidIp(String ip) {
    return ip != null && !ip.isEmpty() && !"unknown".equalsIgnoreCase(ip);
}

前提：Nginx/網關必須正確配置透傳，且應用層**只信任**受信代理層設置的 Header。

JSP 調試頁面模板

<%@ page import="java.util.*,javax.servlet.http.*" %>
<%
    out.println("Protocol: " + request.getProtocol() + "
");
    out.println("Scheme: " + request.getScheme() + "
");
    out.println("Server: " + request.getServerName() + ":" + request.getServerPort() + "
");
    out.println("Remote: " + request.getRemoteAddr() + " / " + request.getRemoteHost() + "
");
    out.println("Method: " + request.getMethod() + "
");
    out.println("URI: " + request.getRequestURI() + "
");
    out.println("Query: " + request.getQueryString() + "
");
    out.println("UA: " + request.getHeader("User-Agent") + "
");
    out.println("Referer: " + request.getHeader("Referer") + "
");
    out.println("X-Forwarded-For: " + request.getHeader("X-Forwarded-For") + "
");
    out.println("All Headers:
");
    Enumeration e = request.getHeaderNames();
    while (e.hasMoreElements()) {
        String n = e.nextElement();
        out.println("  " + n + " = " + request.getHeader(n) + "
");
    }
%>

總結

1. 核心屬性用 HttpServletRequest 標準 API 獲取，Header 用 getHeader/getHeaders。
2. User-Agent 解析**必須**用專業庫 (Yauaa/ua-parser-js)，勿手寫正則。
3. 真實 IP 依賴反向代理正確透傳 `X-Forwarded-For`/`X-Real-IP`，應用層做兜底。
4. 跨語言獲取方式大同小異，均為從請求 Header 讀取。
5. 敏感信息 (Cookie、Authorization) 日誌脫敏，避免洩露。