JSP页面如何使用session获取信息? [英] How to use session in JSP pages to get information?

问题描述

我有一个用于编辑某些用户信息的 JSP 页面.当用户登录网站时，我将信息保留在会话中，然后在我的编辑页面中尝试以下操作:

I have a JSP page used for editing some user's info. When a user logins to the website, I keep the information in the session, then in my edit page I try the following:

<%! String username=session.getAttribute("username"); %>
<form action="editinfo" method="post">
    <table>
        <tr>
            <td>Username: </td><td> <input type="text" value="<%=username %>" /> </td>
        </tr>
    </table>
</form>

但它给出了错误，说会话无法解决.我该怎么办?

but it gives error saying session cannot be resolved. What can I do about it?

推荐答案

JSP implicit 对象如 session、request 等不可用在 JSP 声明中 <%!%> 标签.

JSP implicit objects likes session, request etc. are not available inside JSP declaration <%! %> tags.

你可以直接在你的表达式中使用它作为

You could use it directly in your expression as

<td>Username: </td>
<td><input type="text" value="<%= session.getAttribute("username") %>" /></td>

另外请注意，在 JSP 中使用 scriptlet 早已被弃用.强烈建议使用 EL(表达式语言)和 JSTL 标签.例如，在这里你可以使用 EL 作为

On other note, using scriptlets in JSP has been long deprecated. Use of EL (expression language) and JSTL tags is highly recommended. For example, here you could use EL as

<td>Username: </td>
<td><input type="text" value="${username}" /></td>

最好的部分是范围解析是自动完成的.所以，这里的用户名可以来自页面，或者请求，或者会话，或者应用em> 范围按该顺序.如果对于特定实例，由于名称冲突而需要覆盖它，则可以将范围明确指定为

The best part is that scope resolution is done automatically. So, here username could come from page, or request, or session, or application scopes in that order. If for a particular instance you need to override this because of a name collision you can explicitly specify the scope as

<td><input type="text" value="${requestScope.username}" /></td> or,
<td><input type="text" value="${sessionScope.username}" /></td> or,
<td><input type="text" value="${applicationScope.username}" /></td>

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