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The ValueChangeListener tag registers a ValueChangeListener instance
on the component associated with the enclosing tag. The
ValueChangeListener interface should be implemented by classes that you
want to register with components that publish value change events.
Any component that receives user input, such as one of the HTML
select or text input components, can publish value change events. A
component fires a value change event
when its input changes, but only if the new input is validated
successfully.
You can register several ValueChangeListeners with a component and
they will be invoked in the order that they are registered. An
alternative to this tag is to use a method-binding expression pointing
at a value change listener method of a backing bean on the component
tag itself.
Notice in the example below the use of the JavaScript onchange()
event to trigger form submission when the list selection changes.
Without this JavaScript event, the user must manually submit the form
to invoke the ValueChangeListener.
Example:
<h:selectOneMenu id="optionMenu" value="#{optionBean.selectedOption}" onchange="submit()">
<f:selectItems value="#{optionBean.optionList}" />
<f:valueChangeListener type="com.mycompany.MyValueChangeListenerImpl" />
</h:selectOneMenu>
HTML Output
<select name="form:optionMenu" size="1" onchange="submit()">
<option value="1">Option 1</option>
<option value="2">Option 2</option>
<option value="3">Option 3</option>
</select>
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