Question

I am using JSF 2.0 and PrimeFaces. I have a selectOneMenu and a selectManyCheckbox. I want to achieve this scenario:

When an user chooses:

• option1(PieChart), then the user is allowed to check max one checkbox
• option2(BarChart), then the user is allowed to check max two checkboxes

Here is my attempt so far, the view:

<h:selectOneMenu value="#{bean.chartType}">
    <f:selectItem itemValue="PieChart" itemLabel="PieChart" />
    <f:selectItem itemValue="BarChart" itemLabel="BarChart" />
    <p:ajax event="keyup" update="checkbox" listener="#{bean.checkboxHandler}" />
</h:selectOneMenu>

<h:selectManyCheckbox id="checkbox" value="#{bean.selectedItemscheckbox}">
    <f:selectItem itemValue="priority" itemLabel="By priority" />
    <f:selectItem itemValue="project" itemLabel="By project" />
    <f:selectItem itemValue="issuetype" itemLabel="By IssueType" />
    <f:selectItem itemValue="group" itemLabel="By group" />
</h:selectManyCheckbox>

(note: I am not sure if the <p:ajax event> is correct)

The bean:

public void checkboxHandler() {
    Iterator it1 = selectedItemscheckbox.iterator();
    if (chartType.equals("PieChart")) {
        while (it1.hasNext()) {
            if (selectedItemscheckbox.size() > 1) {
                // Here should be somthing that shows a message to the user.
            }
        }
    }
}

After tring BalusC’s solution,this error occured :

java.lang.InstantiationException: DAOKPI.TestAjax$MyCheckboxValidator
at java.lang.Class.newInstance0(Class.java:340)
at java.lang.Class.newInstance(Class.java:308)
at com.sun.faces.application.ApplicationImpl.newThing(ApplicationImpl.java:1699)
at com.sun.faces.application.ApplicationImpl.createValidator(ApplicationImpl.java:1557)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.createValidator(ValidatorTag     HandlerDelegateImpl.java:238)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyAttachedObject(Validato    rTagHandlerDelegateImpl.java:132)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.applyNested(ValidatorTagHand    lerDelegateImpl.java:205)
at com.sun.faces.facelets.tag.jsf.ValidatorTagHandlerDelegateImpl.apply(ValidatorTagHandlerDel    egateImpl.java:87)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandle     r.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDel    egateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:137)
at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:188)
at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:120)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at com.sun.faces.facelets.compiler.NamespaceHandler.apply(NamespaceHandler.java:93)
at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:98)
at com.sun.faces.facelets.compiler.EncodingHandler.apply(EncodingHandler.java:86)
at com.sun.faces.facelets.impl.DefaultFacelet.apply(DefaultFacelet.java:152)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.buildView(FaceletViewHandlingStrategy.java:769)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:100)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:410)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1534)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)
at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:326)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:227)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:170)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:822)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:719)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1013)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:662)

Update

Thank you problem solved 🙂

Answer 1

You need a custom Validator which throws a ValidatorException when the checkbox contains too many checked items. This Validator needs to be attached to the checkbox component and there should be a <h:message> or a <h:messages> component somewhere in the view which can display the validation error.

The ajax event is wrong. Inside a dropdown, you would like to hook on the change event instead. Inside a checkbox or radio button you would like to hook on click event instead. Both which are already the default when you leave the event attribute to default. Each component should in turn ajax-submit themselves and the other one and finally re-render the message component to reflect the validation error.

In order to figure the selected dropdown value inside the custom validator, the cleanest way would be to set the whole dropdown component as a custom attribute of the checkbox component. This can be achieved by binding the dropdown to the view by binding attribute and specify that as value of <f:attribute> inside the checkbox. The dropdown component and thus also its value can then be obtained inside the custom validator.

Summarized, the below kickoff example should work (note that I used <f:ajax> as <p:ajax> adds no extra advantages in this particular case and I admittedly can’t tell from top of head how and if that would work):

<h:selectOneMenu id="chartType" binding="#{chartType}" value="#{bean.chartType}">
    <f:selectItem itemValue="PieChart" itemLabel="PieChart" />
    <f:selectItem itemValue="BarChart" itemLabel="BarChart" />
    <f:ajax execute="chartType checkbox" render="checkboxmessage" />
</h:selectOneMenu>
<h:selectManyCheckbox id="checkbox" value="#{bean.selectedItemscheckbox}">
    <f:selectItem itemValue="priority" itemLabel="By priority" />
    <f:selectItem itemValue="project" itemLabel="By project" />
    <f:selectItem itemValue="issuetype" itemLabel="By IssueType" />
    <f:selectItem itemValue="group" itemLabel="By group" />
    <f:validator validatorId="myCheckboxValidator" />
    <f:attribute name="chartType" value="#{chartType}" />
    <f:ajax execute="chartType checkbox" render="checkboxmessage" />
</h:selectManyCheckbox>
<h:message id="checkboxmessage" for="checkbox" />

With

@FacesValidator("myCheckboxValidator")
public class MyCheckboxValidator implements Validator {

    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        UIInput chartTypeComponent = (UIInput) component.getAttributes().get("chartType");
        String chartType = (String) chartTypeComponent.getValue();
        List<String> selectedItemscheckbox = (List<String>) value;

        if ("PieChart".equals(chartType) && selectedItemscheckbox.size() > 1) {
            throw new ValidatorException(new FacesMessage("Max 1 item allowed"));
        }
        else if ("BarChart".equals(chartType) && selectedItemscheckbox.size() > 2) {
            throw new ValidatorException(new FacesMessage("Max 2 items allowed"));
        }
    }

}

Note that I assume the #{bean.selectedItemscheckbox} to be a List<String>. If it’s actually a String[], then you need to alter the validator code accordingly.