我可以用这种方式实现HttpSessionListener吗？

Question

我想跟踪我的Java servlet中的有效用户ID，我可以用这种方式实现HttpSessionListener吗？

public class my_Servlet extends HttpServlet implements HttpSessionListener 
{ 
    String User_Id; 
    static Vector<String> Valid_User_Id_Vector=new Vector<String>(); 
    private static int activeSessions=0; 

    public void sessionCreated(HttpSessionEvent se) 
    { 
// associate User_Id with session Id; 
// add User_Id to Valid_User_Id_Vector 
    Out(" sessionCreated : "+se.getSession().getId()); 
    activeSessions++; 
    } 

    public void sessionDestroyed(HttpSessionEvent se) 
    { 
    if (activeSessions>0) 
    { 
// remove User_Id from Valid_User_Id_Vector by identifing it's session Id 
     Out(" sessionDestroyed : "+se.getSession().getId()); 
     activeSessions--; 
    } 
    } 

    public static int getActiveSessions() 
    { 
    return activeSessions; 
    } 

    public void init(ServletConfig config) throws ServletException 
    { 
    } 

    public void destroy() 
    { 

    } 

    protected void processRequest(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException 
    { 
    User_Id=request.getParameter("User_Id"); 
    } 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
    { 
    processRequest(request, response); 
    } 

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
    { 
    processRequest(request, response); 
    } 

    public String getServletInfo() 
    { 
    return "Short description"; 
    } 
} 

如何在会话结束时通知监听器？我试图绕过“/WEB-INF.web.xml”，是否可行？或者它有道理？

Answer 1

这不会绕过/WEB-INF/web.xml。此外，你最终会得到这个类的两个实例，而不是1个执行这两个函数。我建议你把这个Vector放在ServletContext里，并且有2个独立的类。

在servlet中，通过getServletContext()得到它。在监听器，你会做这样的事情：

public void sessionCreated(HttpSessionEvent se) { 
    Vector ids = (Vector) se.getSession().getServletContext().getAttribute("currentUserIds"); 
    //manipulate ids 
}