为什么jsp:include参数不可见 [英] why jsp:include parameters not visible

问题描述

关于访问jsp:param值，我有一个完全相同的基本问题 a>作为此海报；遵循他的榜样对我完全不起作用.通过

I have exactly the same basic question about accessing jsp:param values as this poster; following his example exactly does not work for me. The parameters passed in via jsp:include don't seem to show up in the included file. Is there something peculiar about my setup?

来电者:

<div>
    <jsp:include page="../../../common/callee.jsp">
        <jsp:param name="justinVar" value="primary" />
    </jsp:include>      
</div>

callee.jsp:

callee.jsp:

<i>method 1: [</i><b><%= request.getParameter("justinVar") %></b><i>]</i>
<p/>
<i>method 2: [</i><b>${param.justinVar}</b><i>]</i>
<p/>
<i>method 3: [</i><b>${justinVar}</b><i>]</i>
<p/>

最终输出:

method 1: [null]

method 2: []

method 3: [] 

更新: 以下解决方法可以起作用，这似乎是错误的，但也许它起作用的事实揭示了一些不起作用的地方.

Update: The following workaround does work, it seems wrong, but perhaps the fact that it works reveals something that is not working.

<c:set var="justinVar" value="justinVARisHere" scope="request" />
<jsp:include page="../../../common/callee.jsp" />

推荐答案

要确定问题所在，请尝试通过在EL中打印${param}或在Java代码中打印HttpServletRequest#getParameterMap()来调试/探索整个地图.它必须提供有关真正地图包含的内容的见识.

To nail down the problem, try to debug/explore the entire map by printing ${param} in EL or HttpServletRequest#getParameterMap() in Java code. It must give insights about what the map really contains.

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