有没有办法确定从给定的客户端IP地址创建的活动会话的数量？
解决方法
标准的Servlet API不提供这样的设施.最好的办法是自己维护一个
Map<HttpSession,String>(其中String是IP地址),并在每个
ServletRequest上检查
HttpSession#isNew(),并将其与
ServletRequest#getRemoteAddr()一起添加到地图中.然后可以使用一个活动会话在
Map#values()使用
Collections#frequency().您只需确保在
HttpSessionListener#sessionDestroyed()期间从地图中删除HttpSession.
这一切都可以在实现ServletContextListener,HttpSessionListener和ServletRequestListener的单个监听器中完成.
这是一个开球示例：
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web.xml中定义如下：
<listener>
<listener-class>com.example.SessionCounter</listener-class>
</listener>
您可以在任何servlet中使用它,如下所示：
SessionCounter counter = SessionCounter.getInstance(getServletContext());
int count = counter.getCount("127.0.0.1");
