Invoke action method on click of h:selectOneMenu

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
}

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

1. 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>
   

2. 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

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"%>