what is differences between action and actionlistener in JSF components?

[raminaa niilian]

Hi
can some one tell me what is differences between action and actionlistener in JSF components ?
for example an command button has action and ActionListener properties ,
what is differences between them , when we should use each of them ?

[Chris Schalk]

This is covered in chapter 8 - the Faces event model.

Basically the "action" attribute refers to an action method which returns a String from which the Faces navigation model can use to decide whether or not a navigation is necessary based on the value of the string.

typically one uses an action method to execute some code after a button or link is clicked and then possibly navigate based on the outcome of executed code.

An actionlistener method compared to an action method does not return a String. Instead it returns void. It is basically identical to the action method but instead it just executes the code after an action event (button click or link click) but a navigation is not needed.

A good example of actionlistener could be in response to clicking on a checkbox and having the actionlistener code behind it change a visual attribute of a page such as render a component that was not rendered before..

Chapter 8 has exactly this example where I show how you can have a checkbox when clicked render an additional field in an input form.

-Chris