HttpSession - 如何获取session.setAttribute？ [英] HttpSession - how to get the session.setAttribute?

问题描述

我正在以这种方式创建HttpSession容器：

I'm creating HttpSession container this way:

@SessionScoped
@ManagedBean(name="userManager")
public class UserManager extends Tools
{
  /* [private variables] */
  ...
  public String login() 
  {
    /* [find user] */
    ...
    FacesContext context = FacesContext.getCurrentInstance();
    session = (HttpSession) context.getExternalContext().getSession(true);
    session.setAttribute("id", user.getID());
    session.setAttribute("username", user.getName());
    ...
    System.out.println("Session id: " + session.getId());

我有SessionListener，它应该给我关于创建会话的信息：

And I have SessionListener which should gives me info about session created:

@WebListener
public class SessionListener implements HttpSessionListener
{
  @Override
  public void sessionCreated(HttpSessionEvent event) {    
    HttpSession session = event.getSession();
    System.out.println("Session id: " + session.getId());
    System.out.println("New session: " + session.isNew());
    ...
  }
}

我怎样才能得到用户名属性？

How can I get the username attribute?

如果我正在尝试使用 System.out.println（用户名：+ session.getAttribute（username））它抛出 java.lang.NullPointerException ..

If I'm trying it using System.out.println("User name: " + session.getAttribute("username")) it throws java.lang.NullPointerException..

推荐答案

HttpSessionListener 接口用于监视在应用程序服务器上创建和销毁会话的时间。 HttpSessionEvent.getSession（）返回一个新创建或销毁的会话（取决于它是否被 sessionCreated /调用）分别 sessionDestroyed 。

The HttpSessionListener interface is used to monitor when sessions are created and destroyed on the application server. The HttpSessionEvent.getSession() returns you a session that is newly created or destroyed (depending if it's called by sessionCreated/sessionDestroyed respectively).

如果您想要现有会话，则必须从请求中获取会话。

If you want an existing session, you will have to get the session from the request.

HttpSession session = request.getSession(true).
String username = (String)session.getAttribute("username");

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