查找从给定客户端IP创建的活动会话数 [英] Find number of active sessions created from a given client IP

问题描述

有没有办法确定从给定客户端IP地址创建的活动会话数？

Is there a way to determine the number of active sessions created from a given client IP address?

推荐答案

标准Servlet API不提供相关设施。最好的办法是维护 自己映射< HttpSession，String> （其中 String 是IP地址）并检查每个 ServletRequest 如果 HttpSession＃isNew（） 并将其添加到 Map 以及 ServletRequest＃getRemoteAddr（） 。然后，您可以使用 download.oracle.com/javase/6/docs/api/java/util/Map.html#values%28%29\"rel =noreferrer> Map＃values（） 。您只需要确保在地图中删除​​ HttpSession .oracle.com / javaee / 5 / api / javax / servlet / http / HttpSessionListener.html＃sessionDestroyed％28javax.servlet.http.HttpSessionEvent％29rel =noreferrer> HttpSessionListener #sessionDestroyed（） 。

The standard Servlet API doesn't offer facilities for that. Best what you can do is to maintain a Map<HttpSession, String> yourself (where the String is the IP address) with and check on every ServletRequest if the HttpSession#isNew() and add it to the Map along with ServletRequest#getRemoteAddr(). Then you can get the amount of IP addresses with an active session using Collections#frequency() on Map#values(). You only need to ensure that you remove the HttpSession from the Map during HttpSessionListener#sessionDestroyed().

这一切都可以在一个监听器中实现 ServletContextListener ， HttpSessionListener 和 ServletRequestListener 。

This all can be done in a single Listener implementing the ServletContextListener, HttpSessionListener and ServletRequestListener.

这是一个启动示例：

public class SessionCounter implements ServletContextListener, HttpSessionListener, ServletRequestListener {

    private static final String ATTRIBUTE_NAME = "com.example.SessionCounter";
    private Map<HttpSession, String> sessions = new ConcurrentHashMap<HttpSession, String>();

    @Override
    public void contextInitialized(ServletContextEvent event) {
        event.getServletContext().setAttribute(ATTRIBUTE_NAME, this);
    }

    @Override
    public void requestInitialized(ServletRequestEvent event) {
        HttpServletRequest request = (HttpServletRequest) event.getServletRequest();
        HttpSession session = request.getSession();
        if (session.isNew()) {
            sessions.put(session, request.getRemoteAddr());
        }
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent event) {
        sessions.remove(event.getSession());
    }

    @Override
    public void sessionCreated(HttpSessionEvent event) {
        // NOOP. Useless since we can't obtain IP here.
    }

    @Override
    public void requestDestroyed(ServletRequestEvent event) {
        // NOOP. No logic needed.
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        // NOOP. No logic needed. Maybe some future cleanup?
    }

    public static SessionCounter getInstance(ServletContext context) {
        return (SessionCounter) context.getAttribute(ATTRIBUTE_NAME);
    }

    public int getCount(String remoteAddr) {
        return Collections.frequency(sessions.values(), remoteAddr);
    }

}

在<$ c $中定义c> web.xml 如下所示：

<listener>
    <listener-class>com.example.SessionCounter</listener-class>
</listener>

您可以在以下任何servlet中使用它：

You can use it in any servlet like follows:

SessionCounter counter = SessionCounter.getInstance(getServletContext());
int count = counter.getCount("127.0.0.1");

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