Catching an exception in an JSF page

Question

Hi,
I have made the following example:
In my jsf page I have:
<a4j:commandButton id="save" action="#{settings.save}"
reRender="attributes" />
<h:outputLabel value="Save" for="save" />
<table width="100%" cellpadding="0" cellspacing="0">
<!--
<tr>
<td> If exception occurs add extra buttons here for more actions
</td>
</tr>
-->
<tr>
<td><ui:include src="/attributes.xhtml">
<ui:param name="parent" value="#{settings}" />
</ui:include></td>
</tr>
</table>
In SettingsBean.java
public void save() throws exception
try
doSomething();
catch(Exception e)
// catch the exception here and send it back to the jsf page????
I want to be able to catch the exception when it occurs in my jsf page. If the exception arrises I want to add some extra buttons.
Any ideas how to resolve this?
Thanks in advance

Answer 1

JSF does not work like JSP, even when using JSP with JSF, in that the execution is decoupled from the page being processed. So you cannot catch exceptions in JSF views.
Assuming I have sufficiently confused you now, let me give you some ideas as to how to handle your situation. The usual way this is handled is to register a message when an exception occurs which are then displayed by <h:messages> or <h:message> components.
However, this does not appear to be suitable for your purpose as you require specialized output when the exception occurs. So you could store a flag (or even the exception itself) in a backing bean and use the rendered property of all components to conditionally display your buttons. BUT you will need to take care that the dynamic value of the rendered property will be the same on the subsequent request or the actions for the buttons will not be queued.