Question

我是servlets和jsp的新手。在我的程序中，流程如下：

loginpage.html - ＆gt; controller（servlet - 这里我创建了这样的会话）

HttpSession session = request.getSession(true);
session.setAttribute("uid", uname);
System.out.println("session:"+session.getAttribute("uid"));// shows the value of uid

- ＆GT; create_user.html - ＆GT; conroller（现在它将uid值显示为null） - ＆gt; view_customers.jsp（此处需要uid值，但 null ）。

如何避免会话属性变为空？提前谢谢！

Answer 1

如何避免会话属性变为空？

您可以使用session scope在HttpSessionAttributeListener中监控属性状态（添加/删除/替换）。

示例代码：

public class MySessionAttributeListener implements HttpSessionAttributeListener {

    public MySessionAttributeListener() {
    }

    public void attributeAdded(HttpSessionBindingEvent sessionBindingEvent) {

        // Get the session
        HttpSession session = sessionBindingEvent.getSession();

        // Log some information
        System.out.println("[SessionAttr] " + new java.util.Date()
                + " Attribute added, session " + session + ": " + sessionBindingEvent.getName()
                + "=" + sessionBindingEvent.getValue());
    }

    public void attributeRemoved(HttpSessionBindingEvent sessionBindingEvent) {

        // Get the session
        HttpSession session = sessionBindingEvent.getSession();

        // Log some information
        System.out.println("[SessionAttr] " + new java.util.Date()
                + " Attribute removed, session " + session + ": "
                + sessionBindingEvent.getName());
    }

    public void attributeReplaced(HttpSessionBindingEvent sessionBindingEvent) {

        // Get the session
        HttpSession session = sessionBindingEvent.getSession();

        // Log some information
        System.out.println("[SessionAttr] " + new java.util.Date()
                + " Attribute replaced, session " + session + ": "
                + sessionBindingEvent.getName() + "=" + sessionBindingEvent.getValue());
    }
}

web.xml :(在web.xml中添加以下行）

<listener>
    <listener-class>com.x.y.z.MySessionAttributeListener</listener-class>
</listener>

Servlets-Session属性变为NULL

1 个答案: