JSF中的ActionListener阶段

Question

HI,

I have a doubt on calling the ActionListener method in the JSF beans. For example every request or submission of JSF form is gone through the life cycle of six phases. But, when we are triggering the particular event like action listener or value change listener, is there any lifecycle associated with that request?

Please clarify me.

Answer 1

Any action listener is invoked during invoke action phase, before the real action method. Which action listener methods are to be invoked are determined based on the actionListener attribute of the UICommand component which is associated with the submit.

Any value change listener is invoked during validations phase (or apply request values phase when immediate="true" for the particular UIInput component) after a succesful conversion/validation of the submitted value and only when the submitted value differs from the initial value. Which value change listener methods are to be invoked are determined based on the valueChangeListener attribute of the UIInput components which are associated with the submit.

And no, they do not have their own lifecycle. When they finish executing and return, it's still inside the same phase of the lifecycle. After invoking the valueChangeListener , JSF will continue with conversion/validation of the next UIInput component, or if there are none, then proceed to the next phase. After invoking the actionListener , JSF will continue with the next actionListener or if there are none, invoke the real action method.

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Update : after reading your comments again, I think that I now see your doubt about particularly the value change listener. You seem to think that it by default immediately fires a brand new request to the server side during the client side change event. It does that not by default. You can only achieve this by adding a little piece of JavaScript code which submits the entire HTML form during the change event of the HTML input field.

onchange="this.form.submit()"

This part has nothing to do with JSF. It's a simple HTML attribute. Open the page in webbrowser, rightclick and choose View Source . You'll see that it's there. Disable JavaScript in your browser or remove it in JSF code and you'll see that it won't work anymore. You would need to press the submit button yourself to get it all to run.