I have to dinamically produce a list of tables. Each of these have a variable number of columns (with fixed rows).
To perform this I first put a <p:panelGrid>
inside an <ui:repeat>
: so I correctly produced a list of tables.
Then, to dinamically produce the columns, I tried put both an <ui:repeat>
or a <c:forEach>
inside the <p:panelGrid>
. In the result I obtain no rows.
I written a minimal example here. In the bean testBackingBean
, I have defined (and initialized) the variable ArrayList<ArrayList<String>> tables
. This is the xhtml that does not produce the expected results:
<ui:repeat var="table" value="#{testBackingBean.tables}">
<p:panelGrid>
<f:facet name="header">
<p:row>
<p:column >header of #{table}</p:column>
</p:row>
</f:facet>
<p:row>
<c:forEach var="row" items="${table}">
<p:column>#{row}</p:column>
</c:forEach>
</p:row>
</p:panelGrid>
</ui:repeat>
Noteworthy the header-row correctly converts #{table}
into string. The problem is that I see no rows of data.
Also, if I use the <table>
instead of the <p:panelGrid>
everything work as excpected.
Also, I tried different permutations of <c:forEach>
and <ui:repeat>
with no succes.
So, how can I dinamically produce more tables (using prime-faces) and set a dinamical number of columns?
Thanks!
EDIT: I would like to use two <c:forEach>
, but even with one only <c:forEach>
I get an empty result. In fact if I try the following xhtml:
<c:forEach items="${testBackingBean.tables}" var="tabella">
current element: #{tabella}
</c:forEach>
then I get an empty result. (I know,this is a different question)
The transition from the XHTML source code to the generated HTML output is a two-step process.
First, during view build time, the XHTML source code is parsed and turned in a tree of Java UIComponent
instances representing the JSF UI component tree, as available by FacesContext#getViewRoot()
.
Then, during view render time, the JSF UI component tree produces HTML output and writes it to the HTTP resopnse, starting with UIViewRoot#encodeAll()
method.
Taghandlers like all JSTL <c:xxx>
tags, several JSF <f:xxx>
tags and only a few Facelets <ui:xxx>
tags run during view build time. UI components like all JSF <h:xxx>
tags, several Facelets <ui:xxx>
tags and only a few JSF <f:xxx>
tags run during view render time.
The <c:forEach>
is a taghandler and the <ui:repeat>
is an UI component.
In other words, the UI components which are declared inside <c:forEach>
are recreated multiple times in the JSF component tree based on <c:forEach items>
during view build time which in turn individually produce each their own HTML output during view render time. The UI components which are declared inside <ui:repeat>
are created only once in the JSF component tree during view build time which in turn are reused multiple times based on <ui:repeat value>
to produce HTML output during view render time.
Your concrete problem is caused by the fact that <ui:repeat var="table">
is only available during view render time, not during view build time. The <c:forEach>
is basically retrieving a #{null}
as value when it's about to run during view build time.
You can solve this by replacing the outer <ui:repeat>
by <c:forEach>
. Although I wonder if you couldn't better use <ui:repeat><p:dataTable><p:columns>
instead.