Invoke action method on click of h:selectOneMenu - jsf

Question

I have the following drop down list:
<h:selectOneMenu value="#{user.favCoffee3}" onclick="">
<f:selectItems value="#{user.favCoffee3Value}" var="c"
itemLabel="#{c.coffeeLabel}" itemValue="#{c.coffeeValue}" />
</h:selectOneMenu>
I would like to launch some method from the bean by drop down list item click. How can I achieve it?

Answer 1

You can use the valueChangeListener attribute, pointing to a method in the managed-bean and add a submit() in the onchange attribute.
The form should look like :
<h:form>
<h:selectOneMenu valueChangeListener="#{bean.valueChanged}"
onchange="submit()">
<f:selectItem itemValue="1" itemLabel="First" />
<f:selectItem itemValue="2" itemLabel="Second" />
</h:selectOneMenu>
</h:form>
And the valueChangeListener method in the managed bean would be:
public void valueChanged(ValueChangeEvent event) {
//do your stuff
}

Answer 2

As part of the basic JSF toolkit, you can use the <f:ajax/> tag to submit (using ajax) your input without need for a full page submit/refresh. Using your code sample
Define the <f:ajax/> tag as a child of the dropdown menu
<h:selectOneMenu value="#{user.favCoffee3}" onclick="">
<f:selectItems value="#{user.favCoffee3Value}" var="c" itemLabel="#{c.coffeeLabel}" itemValue="#{c.coffeeValue}" />
<f:ajax listener="#{user.doSomething}"/>
</h:selectOneMenu>
Define a method (doSomething() in this example) in your backing bean that accepts an instance of AjaxBehaviorEvent
public void doSomething(AjaxBehaviorEvent abe){
//do what you want with your favCoffee3 variable here
}
Further reading:
The <f:ajax/> tag documentation by oracle

Answer 3

Seems to work for a4j:support. Your h:selectOneMenu would look like this:
<h:selectOneMenu value="#{user.favCoffee3}">
<f:selectItems value="#{user.favCoffee3Value}" var="c" itemLabel="#{c.coffeeLabel}" itemValue="#{c.coffeeValue}" />
<a4j:support event="onchange" action="#{user.onSelectOneMenuChange}">
</h:selectOneMenu>
You also need to add the following taglib:
<%# taglib uri="http://richfaces.org/a4j" prefix="a4j"%>