如何在Facelets页面中访问会话属性

问题描述

我已经使用JSF和PrimeFaces实现了一个登录表单。
我在PrimeFaces展示网站上使用了。

I have implemented a login form using JSF and PrimeFaces.I used this example in the PrimeFaces showcase website.

我有一个Facelets页面来显示dataTable。现在我需要将上面的登录表单与此表页面集成。所以我在LoginBean.java中添加了几行来处理会话属性。

I have a Facelets page to show a dataTable. Now I need to integrate the above login form with this table page. So I added few lines in to LoginBean.java to handle session attribute.

     if (username.equals(getUsername_db()) && password.equals(getPassword_db())) {//valid user and paward
        loggedIn = true;
        msg = new FacesMessage(FacesMessage.SEVERITY_INFO, "Welcome", getUsername_db());
        //new lines
        FacesContext context2 = FacesContext.getCurrentInstance();
        HttpSession session = (HttpSession) context2.getExternalContext().getSession(true);
        session.setAttribute("user", username);
        //end of new lines
        ...

我需要隐藏如果用户未登录，则来自dataTable的列。
现在我的问题是，如何在我的Facelets页面中访问会话属性？

I need to hide a column from the dataTable, if the user is not logged in.Now my problem is, how can I access session attribute inside my Facelets page?

推荐答案

您已将登录用户存储为名为user的会话属性。

You've stored the logged-in user as a session attribute with the name "user".

所以它在EL中可用作为如下：

So it's in EL available as follows:

#{user}

您可以在EL中使用空关键字来检查它是否存在（即是否已登录）和您可以使用JSF组件的呈现的属性来指示是否生成HTML输出。

You can just use the empty keyword in EL to check if it's present or not (i.e. if it's logged-in or not) and you can use JSF component's rendered attribute to instruct whether to generate HTML output or not.

<h:panelGroup rendered="#{not empty user}">
    <p>Welcome #{user}, you have been logged in!</p>
</h:panelGroup>

在隐藏表列的特定情况下，只需按如下方式使用它：

In your specific case of hiding a table column, just use it as follows:

<p:column rendered="#{not empty user}">
    ...
</p:column>

存储会话属性的更好方法是使用 ExternalContext＃getSessionMap（） 。这样你的代码就没有臭 javax.servlet。* imports。

A nicer way to store a session attribute is using ExternalContext#getSessionMap(). This way your code is free of smelly javax.servlet.* imports.

FacesContext.getCurrentInstance().getExternalContext().getSessionMap().put("user", username);

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无关到具体问题，为什么进行以下检查？

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Unrelated to the concrete problem, why the following check?

if (username.equals(getUsername_db()) && password.equals(getPassword_db())) {

为什么不进行 SELECT ... FROM用户WHERE用户名=？ SQL中的AND password =？？或者你不相信它返回右行的数据库？

Why don't you just do a SELECT ... FROM user WHERE username=? AND password=? in SQL? Or don't you trust the DB that it returns the right row?

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