JSF h:selectOneMenu is never set even when using f:ajax - jsf

Question

I want to implement a filtering facility in a JSF web application as follows: The users can add as many filters as they want. They can also delete them. So I am having a dataTable of filters. Each row consists of one h:selectOneMenu which has an ajax “change” event in order to make a second h:selectOneMenu visible in the same row. The options of the second h:selectOneMenu are calculated dynamically according to the selected option of the first.
The problem is that the value of second h:selectOneMenu is never set to the back-end object even if I added an ajax event. However the value of the first h:selectOneMenu is set.
I have the following fragment of code in an .xhtml page:
<h:form id="filterForm">
<h:dataTable id="filterTable" value="#{filterManager.filters}" var="filter">
<h:column>
<h:outputLabel value="#{msgs.filterBy}:" for="availableFilters" />
<h:selectOneMenu id="availableFilters" value="#{filter.filter}">
<f:selectItems value="#{filterManager.getProperties(typeSelector.typeSelected)}" />
<f:ajax event="change" render=":filterForm" />
</h:selectOneMenu>
</h:column>
<h:column>
<h:panelGroup id="filterValuesPanel" >
<h:outputLabel value="#{msgs.value}:" for="filterValues" rendered="#{!filter.filterEmpty}" />
<h:selectOneMenu value="#{filter.value}" id="filterValues" rendered="#{!filter.filterEmpty}" >
<f:selectItems value="#{filterManager.getPossibleAnswers(filter)}" />
<f:ajax event="change" render=":filterForm" />
</h:selectOneMenu>
</h:panelGroup>
</h:column>
<h:column>
<h:commandButton value="#{msgs.delete}" title="#{msgs.deleteFilter}">
<f:ajax event="click" listener="#{filterManager.removeFilter(filter)}" render=":filterForm" />
</h:commandButton>
</h:column>
</h:dataTable>
<h:commandButton value="#{msgs.addNewFilter}">
<f:ajax event="click" listener="#{filterManager.addNewFilter}" render=":filterForm" />
</h:commandButton>
</h:form>
I have a bean called “FilterManager” which has a ViewScoped. Important parts are shown below:
#ManagedBean
#ViewScoped
public class FilterManager implements Serializable {
private List<Filter> filters; // it has a getter
private int currentFilterId;
public void addNewFilter(AjaxBehaviorEvent event) {
this.currentFilterId++;
this.filters.add(Filter.getEmptyFilter(this.currentFilterId));
}
public void removeFilter(Filter filter) {
this.filters.remove(filter);
}
...
}
The Filter class is a normal class (not a bean) and is shown below:
public class Filter implements Serializable {
private int id;
private String filter;
private String value;
public String getFilter() {
return filter;
}
public void setFilter(String theFilter) {
if (theFilter != null && !theFilter.isEmpty())
this.filter = theFilter;
}
public String getValue() {
return value;
}
public void setValue(String theValue) {
this.value = theValue;
}
public boolean isFilterEmpty() {
return this.filter == null || this.filter.isEmpty();
}
...
}
Notice that TypeSelector is a SessionScoped bean which has a typeSelected property along with getter and setter.
The problem is: filter.filter is set correctly whereas filter.value is never set. I can't find the problem so I need your help please. Apologies for all this code but I needed to provide you with all the necessary details.
Thanks in advance!

Answer 1

Okay guys that was my fault. I had a bug in FilterManager.getPossibleAnswers(Filter filter) method. Basically, at the end of the method, I was setting filter.value to the first element of List unconditionally. Eg instead of writing
if (filter.getValue() == null || filter.getValue().isEmpty()) {
SelectItem first = answers.get(0);
filter.setValue((String) first.getValue());
}
I just wrote:
SelectItem first = answers.get(0);
filter.setValue((String) first.getValue());
Although filter.value was updating as normal, the value was changing back to default (first element in list) during re-rendering of dataTable component.