How can the dependencies between drop downs be managed? - jsf

Question

I am using JSF2.0. I have three drop downs :
masterDropDown.
childDropDownA
childDropDownB
The business rule that needs to be enforced is :
Whenever masterDropDown changes , I need to populate childDropDownA and childDropDownB.
The contents of childDropDownA and childDropDownB are same except that when the user selects something from childDropDownA, childDropDownB should have its old contents except the one selected by user in childDropDownA. The same rule applies when the user selects childDropDownB first.
What is the cleanest way to achieve this in JSF?

Answer 1

Plain JSF 2:
<h:form>
<h:selectOneMenu id="ddlMaster" value="#{bean.ddlMasterSelected}">
<f:listItems value="#{bean.ddlMasterData}" />
<f:ajax listener="#{bean.fillChildren}" render="ddlChildA ddlChildB" />
</h:selectOneMenu>
<h:selectOneMenu id="ddlChildA" value="#{bean.ddlChildASelected}">
<f:listItems value="#{bean.ddlChildAData}" />
<f:ajax listener="#{bean.refillChildB}" render="ddlChildB" />
</h:selectOneMenu>
<h:selectOneMenu id="ddlChildB" value="#{bean.ddlChildBSelected}">
<f:listItems value="#{bean.ddlChildBData}" />
<f:ajax listener="#{bean.refillChildA}" render="ddlChildA" />
</h:selectOneMenu>
</h:form>
Managed bean
#ManagedBean
#ViewScoped
public class Bean {
private Map<String, String> ddlMasterData;
private Map<String, String> ddlChildAData;
private Map<String, String> ddlChildBData;
private String ddlMasterSelected;
private String ddlChildASelected;
private String ddlChildBSelected;
#PostConstruct
public void init() {
//fill initial values for the drop down lists...
//this is a raw idea, you must refine it
DDLService ddlService = new DDLService();
ddlMasterData = ddlService.getDDLMasterData();
//empty data for children ddls
ddlChildAData = new LinkedHashMap<String, String>();
ddlChildBData = new LinkedHashMap<String, String>();
}
public void refillChildB(AjaxBehaviorEvent event) {
//filling the children ddls
DDLService ddlService = new DDLService();
ddlChildASelected = ddlService.getDDLChildData();
//same method to fill child data on ddlChildBSelected because is same data
ddlChildBSelected = ddlService.getDDLChildData();
}
public void fillChildren(AjaxBehaviorEvent event) {
//when the user selects something from childDropDownA
//childDropDownB should have its old contents
//I assume it must be cleared, you can change this behavior though
ddlChildBData = new LinkedHashMap<String, String>();
}
public void refillChildA(AjaxBehaviorEvent event) {
//The same rule applies when the user selects childDropDownB first
//I assume it must be cleared, you can change this behavior though
ddlChildAData = new LinkedHashMap<String, String>();
}
}