假如用代理服务器，request.getRemoteAddr(); 只能得到代理服务器地址
以下方法是得到正确所有ip的方法
在jsp声明这个函数

<%!public String getIpAddr(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;     
}%>

嵌入jsp网页中，然后用

<%String ip=getIpAddr(request);%>

得到访问者ip
ip就是访问者的ip，你保存到数据库或者缓存中，就由你自己了