在servlet和jsp中检查会话 [英] checking session in servlet and jsp

问题描述

在我的网络应用程序中我需要检查会话是否已经存在。

In my web application i neet to check session already exist or not.

我想在我的servlet和jsp中检查这个。

i want to check this in my servlet and in jsp also.

有没有办法检查这个。

谢谢

推荐答案

您可以使用 HttpServletRequest＃getSession（boolean create） ， create = false 。如果尚未创建，它将返回null。

You can test it with HttpServletRequest#getSession(boolean create) with create=false. It will return null if not created yet.

HttpSession session = request.getSession(false);
if (session == null) {
    // Session is not created.
} else {
    // Session is already created.
}

如果你确实想要创建会话，如果它不存在，然后抓住它并使用 HttpSession＃isNew（） ：

If you actually want to create the session anyway if it doesn't exist, then just grab it and test the freshness using HttpSession#isNew():

HttpSession session = request.getSession();
if (session.isNew()) {
    // Session is freshly created during this request.
} else {
    // Session was already created during a previous request.
}

这就是你在Servlet中的表现。在JSP中，您只能在JSTL和EL的帮助下测试新鲜度。你可以通过 PageContext＃getSession（） 然后只需在其上调用 isNew（）。

That was how you would do it in a Servlet. In a JSP you can only test the freshness with help of JSTL and EL. You can grab the session by PageContext#getSession() and then just call isNew() on it.

<c:if test="${pageContext.session.new}">
    <p>Session is freshly created during this request.</p>
</c:if>

或

<p>Session is ${pageContext.session.new ? 'freshly' : 'already'} created.</p>

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