Primefaces dependent selectOneMenu and required="true"

Question

In my application I have three dropdown menu (p:selectOneMenu), say A, B, C. Among them two are dependent, say B and C. By changing the value of B I am dynamically loading values to C. Also there is a textbox. The value of the textbox is generating by ajax when the on-change event is firing from these three dropdowns.

Here is the xhtml:

<p:selectOneMenu id="customerMenu" value="#{adminController.activityDTO.customerId}" required="true" label="Customer Name" style="width: 200px">
    <f:selectItem itemLabel="Select One" itemValue="" />
    <f:selectItems value="#{adminController.customers}" var="customer" itemLabel="#{customer.customerName}" itemValue="#{customer.customerId}" />
    <p:ajax listener="#{adminController.generateActivityName}" update="activityId" />                       
</p:selectOneMenu>

<p:selectOneMenu id="activityTypeMenu" value="#{adminController.activityDTO.activityParentType}" required="true" label="Activity Type"
    style="width: 200px">
    <f:selectItem itemLabel="Select One" itemValue="" />
    <f:selectItems value="#{adminController.activityTypes}" var="activityType" itemLabel="#{activityType.parent}" itemValue="#{activityType.parent}" />
    <p:ajax listener="#{adminController.updateDependentActivity}" update="activitySubType" />
</p:selectOneMenu>

<p:selectOneMenu id="activitySubTypeMenu" value="#{adminController.activityDTO.activitySubType}" required="true" label="Activity Sub Type"
    style="width: 200px">
    <f:selectItem itemLabel="Select One" itemValue="" />
    <f:selectItems value="#{adminController.activitySubTypes}" var="activityType" itemLabel="#{activityType.name}" itemValue="#{activityType.id}" />
    <p:ajax listener="#{adminController.generateActivityId}" update="activityId" />
</p:selectOneMenu>

<p:inputText id="activityId" autocomplete="off" readonly="true" value="#{adminController.activityDTO.activityId}"
    label="#{adbBundle['admin.addActivityPanel.addActivityTable.activityId']}" required="true" />

The activityTypeMenu and activitySubTypeMenu are dependent, by the selected value of the activityTypeMenu I am populating the activitySubTypeMenu.

Now the problems that I am facing is:

• Say I have select "External" and "Internal" in activityTypeMenu and default "Select One". If I choose "External" from activityTypeMenu the activitySubTypeMenu will have "Project" and "Service". But then if I choose the default "Select One" the activitySubTypeMenu is still holding the previously dynamically populated values. This is because the required="true" attribute resisting to fire the backend method from which I am loading the dynamic value.
• I have tried to set the itemValue of <f:selectItem itemLabel="Select One" itemValue="" /> to #{null} and then the backend method is firing on selecting the "Select one" option and I can set an empty list to activitySubTypes and this way the activitySubTypeMenu get empty. But in that case the required="true" is getting meaningless. I mean, I also have save button and on clicking that button without selecting any option (that is selecting "Select one") from activityTypeMenu and activitySubTypeMenu not throwing ValidatorException and the components are not getting styled by the error css class of Primefaces.
• Also if I don't set the itemValue of <f:selectItem itemLabel="Select One" itemValue="" /> to #{null} then on-changing to selected value to default option("Select one") does not clearing out the activityId p:inputText. If I use #{null} then I can get the backend method firing from which I can set the value of the textbox to empty.

How ca i solve this issues and get desired result. What I want are:

• If the option is set to "Select one" then the dependent menu will be empty and that of the textbox.
• I want to use the required="true" attribute.

Answer 1

You can use EL in the required attribute. You can let the desired expression evaluate true only when a particular submit button is pressed, or when a particular component value is submitted (and thus by its client ID present in the request parameter map #{param}).

The following kickoff example should do what you need.

<p:selectOneMenu binding="#{menu1}" ... required="#{not empty param[submit.clientId]}">
    ...                       
</p:selectOneMenu>
<p:selectOneMenu ... required="#{not empty param[menu1.clientId]}">
    ...                       
</p:selectOneMenu>
<p:commandButton binding="#{submit}" ... />

This way, the 1st menu is only required when the form's main submit button is pressed (and thus not when event listeners are fired) and the 2nd menu is only required when the 1st menu has a value.