why jsp:include parameters not visible

问题

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?

Caller:

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

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/>

Final output:

method 1: [null]

method 2: []

method 3: []

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" />

回答1:

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.

回答2:

Right. I have had a similar problem that for the last hour or so and I have found a solution for my case.

I had index.jsp and tried to include news.jspf in it with text from a jsp param in the index.jsp It didn't work. It just showed the news.jspf EL as normal text.

I changed the included file name extension from .jspf to .jsp and it fixed the problem.

I'm using Eclipse, which may or may not be a factor.

Good luck

回答3:

I've traced down the generated java source and it looks reasonable. Either one of two things are happening: org.apache.jasper.runtime.JspRuntimeLibrary.URLEncode is messing up the varible name, or the classloader used resolves to JspRuntimeLibrary to some other instance than the one driving the web app.

// caller.jsp ....
org.apache.jasper.runtime.JspRuntimeLibrary.include(request, response, 
  "callee.jsp" + (("callee.jsp").indexOf('?')>0? '&': '?') + 
  org.apache.jasper.runtime.JspRuntimeLibrary.URLEncode("justinVar",
  request.getCharacterEncoding())+ "=" +
  org.apache.jasper.runtime.JspRuntimeLibrary.URLEncode("primary", 
  request.getCharacterEncoding()), out, true
);

Looking inside Jasper's runtime, we find this gem. Its not clear that this is the problem, however the page being rendered is jsp:include from defaultParent.jsp, although jsp:params passed into the jsp:include from defaultParent don't seem to show up either.

  958           // FIXME - It is tempting to use request.getRequestDispatcher() to
  959           // resolve a relative path directly, but Catalina currently does not
  960           // take into account whether the caller is inside a RequestDispatcher
  961           // include or not.  Whether Catalina *should* take that into account
  962           // is a spec issue currently under review.  In the mean time,
  963           // replicate Jasper's previous behavior

回答4:

This work in my Liferay portlet

ParamUtil.getString(PortalUtil.getOriginalServletRequest(request), "justinVar")

回答5:

This issue can happen if the request is wrapped (i.e. HttpServletRequestWrapper), likely via a filter. See: jsp:param no longer sets parameters when original request is wrapped with a HttpServletRequestWrapper

来源：https://stackoverflow.com/questions/5780314/why-jspinclude-parameters-not-visible

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param