How to use c:forEach with p:dataTable and p:columnGroup? - jsf

Question

I want to use a special form of grouping 'dynamic' columns. This is however not supported as stated in my other question. Using c:forEach was suggested as a possible solution
Which is correct way to use c:forEach for defining table header and colums.
My code BEFORE:
<p:dataTable id="resultTable" var="result" value="#{myBean.searchResults}" scrollable="true">
<p:columns value="#{myBean.columns}" var="column" columnIndexVar="colIndex">
<f:facet name="header" >
<h:outputText value="#{column.header}"/>
</f:facet>
<h:outputText value="#{result[column.property]}"/>
</p:columns>
</p:dataTable>
and code AFTER transformation (didn't work - table is not displayed):
<p:dataTable id="resultTable" var="result" value="#{myBean.searchResults}" scrollable="true">
<p:columnGroup type="header">
<p:row>
<c:forEach items="#{myBean.columns}" var="column">
<p:column headerText="#{column.header}"/>
</c:forEach>
</p:row>
</p:columnGroup>
<c:forEach items="#{myBean.columns}" var="column" >
<p:column>
<h:outputText value="#{result[column.property]}"/>
</p:column>
</c:forEach>
</p:dataTable>
PrimeFaces version 3.4.1

Answer 1

The "by the book" way to create dynamic columns would be to use the "Dynamic Columns" feature of the data table.
Any way, I did something very similar to what you are trying to do in the past, using c:forEach. The only difference was that I was not using p:columnGroup at the same time.
So, code like
<p:dataTable id="resultTable" var="result" value="#{myBean.searchResults}" scrollable="true">
<c:forEach items="#{myBean.columns}" var="column" >
<p:column headerText="#{column.header}">
<h:outputText value="#{result[column.property]}"/>
</p:column>
</c:forEach>
</p:dataTable>
should really work. When you do this way, you add p:column objets in the component tree before the p:datatable analyze the tree. So, this does the trick.
Beware that this can lead to problems in edge, ajax cases. So, if you can, just stick to the built-in dynamic columns feature.