Any way to list request header names with JSF EL -- without backing bean? - jsf

Question

Is there any way to use JSF EL (Java EE 7) to list all the request's header names and corresponding values in a 2-column table, without introducing a backing bean? I can do it if I create a bean and access that from EL, so I do have a means to the end -- but the thing I'm trying to figure out is if it can be done entirely with "out of the box" EL. "That's not possible" would be a fine answer -- I'm still learning.
I thought something like this:
<table>
<ui:repeat value="#{request.getHeaderNames()}" var="hdr">
<tr>
<td>#{hdr}</td>
<td>#{headerValues[hdr]}</td>
</tr>
</ui:repeat>
</table>
But that gives a 1-row table, something like this:
org.apache.catalina.util.Enumerator#2dbf763b [Ljava.lang.String;#74eb32f3
I suspect that because request.getHeaderNames() is giving an enumerator instead of a list of some kind that ui:repeat wants, this approach won't work at all, and I need to do something fundamentally different.

Answer 1

You can just iterate over #{headerValues} itself. You only need either JSTL <c:forEach>,
<dl>
<c:forEach items="#{headerValues}" var="entry">
<dt>#{entry.key}</dt>
<c:forEach items="#{entry.value}" var="headerValue">
<dd>#{headerValue}</dd>
</c:forEach>
</c:forEach>
</dl>
or to make use of EL 2.2 feature to convert Map to Entry[] as follows, as <ui:repeat> doesn't support maps but only lists and arrays:
<dl>
<ui:repeat value="#{headerValues.entrySet().toArray()}" var="entry">
<dt>#{entry.key}</dt>
<ui:repeat value="#{entry.value}" var="headerValue">
<dd>#{headerValue}</dd>
</ui:repeat>
</ui:repeat>
</dl>
Note that each value of #{headerValues} represents a String[], so I've fixed that for you as well, with a proper data structure.