Setting datatable sortBy attribute dynamically from managed bean - jsf

Question

We wanted to have are datatables bookmarkable, so the state of the datatable is carried in URL (offset, limit, sortOrder, sortBy, etc). The problem is I need to get the actual sortBy value for the datatable from the managed bean and set it dynamically (not statically as in the implementation).
We extended the DataTable code so the dynamic value of sortBy can evaluate. The code below does the trick, when referencing the property using the bean name:
CustomDataTable.java
#Override
protected String resolveSortField() {
UIColumn column = this.getSortColumn();
String sortField = null;
ValueExpression sortVE = this.getValueExpression("sortBy");
if(column == null) {
sortField = resolveDynamicField(sortVE);
}
else {
if(column.isDynamic()) {
((DynamicColumn) column).applyStatelessModel();
sortField = resolveDynamicField(sortVE);
} else {
sortField = resolveStaticField(sortVE);
}
}
return sortField;
}
#Override
public String resolveDynamicField(ValueExpression expression) {
if(expression != null) {
String expressionString = expression.getExpressionString();
if (expressionString.startsWith("#{")) {
FacesContext context = getFacesContext();
ELContext eLContext = context.getELContext();
ValueExpression dynaVE = context.getApplication()
.getExpressionFactory().createValueExpression(eLContext, expressionString , String.class);
String result = (String) dynaVE.getValue(eLContext);
if (StringUtils.isNotEmpty(result)) {
return result;
} else {
return resolveStaticField(expression);
}
} else {
return expressionString.substring(expressionString.indexOf(".") + 1);
}
} else {
return null;
}
}
In template:
<p:dataTable value="#{concreteBean.dataModel}"
var="obj"
selection="#{concreteBean.selected}"
selectionMode="single"
sortBy="#{concreteBean.sortBy}"
sortOrder="#{concreteBean.sortOrder}"
first="#{concreteBean.first}"
rows="#{concreteBean.rows}"
rowKey="#{obj}">
...
However we needed to refactor the template because of duplications and now we include the datatable and giving it the managed bean through ui:param:
...
<ui:param name="bean" value="#{concreteBean}" />
<ui:include src="datatable.xhtml" />
...
...
<p:dataTable value="#{bean.dataModel}"
var="obj"
selection="#{bean.selected}"
selectionMode="single"
sortBy="#{bean.sortBy}"
sortOrder="#{bean.sortOrder}"
first="#{bean.first}"
rows="#{bean.rows}"
rowKey="#{obj}">
...
However the dynamic value in this case evaluates to empty string and not the property value of the referencing bean (getter for sortBy is not called at all).
Can anyone help to do some magic, so the value of sortBy attribute can be dynamically set from the property of the managed bean?

Answer 1

Turns out I can simply evaluate the sortBy attribute by calling DataTable.getSortBy(), which uses StateHelper the same way as the regular attributes do when evaluating the value.