error in calling a valueChangeListener method on "listener" attribute on for event="valueChange"

Question

I am using following specs:

JSF 2.0, Netbeans 7.1.2 with JDK 1.6 and Glassfish 3.1.2

Below is my index.xhtml code:

<h:form>
    <h:panelGrid columns="2">
        <h:outputText value="Select a country:" />
        <h:selectOneMenu id="countryBox" value="#{ab.selCountry}">
            <f:selectItem itemLabel="India" itemValue="India" />
            <f:selectItem itemLabel="United States of America" itemValue="USA" />
            <f:ajax execute="countryBox" render="stateBox" event="valueChange" listener="#{ab.result}"/>
        </h:selectOneMenu> 
        <h:outputText value="Select a state:" />
        <h:selectOneMenu value="#{ab.country}" id="stateBox">
            <f:selectItems value="#{ab.state}" />
        </h:selectOneMenu>
    </h:panelGrid>
</h:form>

and here is my AJAXBean.java code:

@ManagedBean (name="ab")
@RequestScoped
public class AJAXBean {

    /**
     * Creates a new instance of AJAXBean
     */

    private List<SelectItem> country;
    private List<SelectItem> state;
    private String selCountry;

    // getters and setters of properties

    public AJAXBean() 
    {
        country = new ArrayList<SelectItem>();
        state = new ArrayList<SelectItem>();
    }

    public void result(ValueChangeEvent vce) // valueChangeListener for ajax call. Is this valid?
    {
        System.out.println("Inside valueChangeListener");

        String value = (String) vce.getNewValue();
        state.clear();

        if (value.equals("India"))
        {
            state.add(new SelectItem("Maharashtra"));
            state.add(new SelectItem("Madhya Pradesh"));
            state.add(new SelectItem("Andhra Pradesh"));
            state.add(new SelectItem("Uttar Pradesh"));
            state.add(new SelectItem("Rajasthan"));

        }
        else if (value.equals("USA"))
        {
            state.add(new SelectItem("Missouri"));
            state.add(new SelectItem("Kentucky"));
            state.add(new SelectItem("North Carolina"));
            state.add(new SelectItem("South Carolina"));
            state.add(new SelectItem("Colorado"));

        }
    }
}

Basically what I'm trying to do here is:

One fires an AJAX call on event="valueChange" and listener="#{ab.result}". The result method here modifies the value of 'state' list (of SelectItems).

Is the syntax of my value change listener method correct? Because when I try to execute this, it shows me an alert box stating the MethodNotFoundException + the method #{ab.result(AJAXBehaviorEvent)} not found i.e. it is trying to search for a "result" method which catches an AJAXBehaviorEvent object. So , my question is, Is the signature for a value change listener method any different when it is used with f:ajax call?

PS: It tried to use #{ab.result()}. In this case, it simply says MethodNotFoundException. and If is use #{ab.result(vce)} instead of #{ab.result()} / #{ab.result}, it gives me a NullPointerException.

If I put the same function in valueChangeListener attribute of my h:selectOneMenu, it works,. I mean, obviously it will work. But that does not solve my purpose. My purpose is a simple ajax call on valueChange event which updates a list in the bean and re-renders (a second) linked h:selectOneMenu as a result

What is wrong with my code?

takes AJAXBehaviourEvent and the valueChangeListener takes ValueChangeEvent. You just misplaced it. — h-kach, Feb 20 '13 at 12:33
@hemanth, you're right, why don't you post a detailed answer — kolossus, Feb 20 '13 at 13:01
@kolossus Sorry I didnt have time for a detailed answer, just wanted to give OP a heads-up. — h-kach, Feb 21 '13 at 05:25

score 3 · Accepted Answer · edited Jun 20 '20 at 09:12

Listen to the exception you got. It says that it cannot find the method with the AjaxBehaviorEvent argument. Change the ValueChangeEvent argument by the AjaxBehaviorEvent argument.

public void result(AjaxBehaviorEvent event) {
    // ...
}

Instead of ValueChangeEvent#getNewValue(), just access selCountry directly.

By the way, the event="valueChange" is the default setting already. Just get rid of it to reduce code noise.

error in calling a valueChangeListener method on "listener" attribute on for event="valueChange"

1 Answers1

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