如何使用 EL 在 JSP 中获取 request/session/servletcontext 属性? [英] How to obtain request / session / servletcontext attribute in JSP using EL?

问题描述

我知道这并不难，但我运气不好.

I know this isn't hard, but I'm not having any luck.

我想让 fooList 从一个 JSP 中的 Servlet 可用.所以在 Servlet 中我有:

I want to make fooList from a Servlet available in a JSP. So in the Servlet I have:

request.setAttribute("list", fooList);
RequestDispatcher dispatcher = 
  getServletContext().getRequestDispatcher("/myJsp.jsp");
dispatcher.forward(request, response);

然后在 JSP 中，我想要:

Then in the JSP, I want:

<c:forEach var="post" items="${SOME_EL_HERE}">
    <!-- stuff -->
</c:forEach>

其中 SOME_EL_HERE 是检索我在 request 上设置的属性的表达式.

Where SOME_EL_HERE is an expression that retrieves the attribute that I have set on the request.

有什么想法吗?我的偏好是不通过添加框架使简单的任务复杂化，但我愿意改变策略.

Any thoughts? My preference is to not complicate a simple task by adding a framework, but I'm open to changes in strategy.

推荐答案

这只是您在此处设置的属性 name:

It's just the attribute name as you've set yourself here:

request.setAttribute("list", fooList);

就是这样 "list":

${list}

这对 session.setAttribute("name", value) 和 application.setAttribute("name", value) 的工作方式相同.该值在 EL 中仅通过 ${name} 可用.

This works the same way for session.setAttribute("name", value) and application.setAttribute("name", value). The value is in EL available by just ${name}.

更多细节:EL 默认使用 PageContext#findAttribute() 随后扫描页面、请求、会话和应用程序范围，寻找匹配给定属性名称的第一个非空属性值.

More detail: EL uses by default PageContext#findAttribute() which scans in subsequently the page, request, session and application scopes for the firstnext non-null attribute value matching the given attribute name.

如果你想为你在不同范围内有多个同名属性的情况明确指定范围，那么通常的方法是使用 ${pageScope}, ${requestScope}、${sessionScope} 或 ${applicationScope}.例如

If you'd like to explicitly specify the scope for the case that you've multiple attributes with the same name in different scopes, then normal approach is to use ${pageScope}, ${requestScope}, ${sessionScope} or ${applicationScope}. E.g.

${requestScope.list}

另见:

• Java EE 5 中的统一表达式语言教程

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