若用nginx做反向代理後，直接用String ip = request.getRemoteAddr();

獲取的將是nginx伺服器所在ip地址，不能獲取瀏覽器真實ip地址！

第一步：在nginx中新增如下配置：

    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header REMOTE-HOST $remote_addr;

    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

如下圖所示：

第二步：獲取真實ip地址

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();
}