java - 我可以这样实现 HttpSessionListener 吗？

Question

我正在尝试在 Java servlet 中跟踪有效的用户 ID，我可以通过这种方式实现 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 session 结束时通知监听器？我正在尝试一起绕过“/WEB-INF.web.xml”，这可行吗？或者说有道理吗？

Answer 1

这不会绕过/WEB-INF/web.xml。此外，您最终将得到该类的 2 个实例，而不是 1 个执行这两个功能。我建议你把这个 vector 放在ServletContext中并有 2 个独立的类。

在 servlet 中，您可以通过 getServletContext() 访问它。在监听器中，您将执行以下操作:

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