JavaServlet中获取客户端IP与MAC地址的方法

在开发Web应用时，有时需要获取客户端的IP地址以及MAC地址来增强系统的安全性和功能性。本文将通过一个简单的Java Servlet实例来展示如何实现这一功能。

package com.example.servlets;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ClientInfoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String clientIp = getClientIpAddress(request);
        String clientMac = getMACAddress(clientIp);
        System.out.println("Client IP: " + clientIp);
        System.out.println("Client MAC: " + clientMac);

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("");
        out.println("");
        out.println("  ");
        out.println("  ");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the POST method");
        out.println("  ");
        out.println("");
        out.flush();
        out.close();
    }

    private String getClientIpAddress(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();
        }
        return ip;
    }

    private String getMACAddress(String ip) {
        String str = "";
        String macAddress = "";
        try {
            Process p = Runtime.getRuntime().exec("nbtstat -A " + ip);
            InputStreamReader ir = new InputStreamReader(p.getInputStream());
            LineNumberReader input = new LineNumberReader(ir);
            for (int i = 1; i <100; i++) {
                str = input.readLine();
                if (str != null) {
                    if (str.indexOf("MAC Address") > 1) {
                        macAddress = str.substring(str.indexOf("MAC Address") + 14, str.length());
                        break;
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace(System.out);
        }
        return macAddress;
    }
}

以上代码展示了如何在Java Servlet中获取客户端的IP地址和MAC地址。首先，通过请求头信息尝试获取客户端的真实IP地址，如果这些头信息不存在或无效，则使用HttpServletRequest的getRemoteAddr方法作为备选方案。对于MAC地址的获取，通过执行命令行工具nbtstat来查询指定IP地址对应的MAC地址，并从命令输出中解析出MAC地址。

需要注意的是，这种方法依赖于操作系统的命令行工具，可能在不同的操作系统上表现不同。此外，获取客户端MAC地址通常仅限于局域网环境，在广域网环境下可能无法实现，因为大多数网络设备会隐藏或更改客户端的真实MAC地址以保护用户隐私。