How to pass get-parameter to backing bean in jsf?

I have a get-parameter with name controller. When I try to pass it (with propertyChangeListener) to my backing bean I get null instead of the real value of that parameter:

<h:commandButton value="#{msg['mail.send']}" styleClass="mailbutton" action="#{mailSender.sendMail}">
   <f:setPropertyActionListener target="#{mailSender.controllerName}" value="{#param.controller}"/>
</h:commandButton>

So, I have two questions:

1. What is the proper way to set bean property with a开发者_如何学JAVA get-parameter value? Actually, I've already get the value from ExternalContext#getRequestParam but maybe there are some other solutions.
2. More interesting question: why propertyActionListener didn't work here? What does it do actually? (again I have some thoughts about it but it would be nice to read more comprehensive explanations).

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First, a h:commandButton fires a POST request, not a GET request. To fire a GET request, you need h:outputLink. To set a GET parameter, you need f:param. To set it as a bean property, define it as <managed-property> in faces-config.xml with a value of #{param.name}. More hints and code examples can be found here.

Second, your code is invalid. The f:setPropertyActionListener value should have been #{param.controller}. And to get it to work, the #{param.controller} should already be there during the initial request. It does not automagically set the value in the subsequent request as you seem to expect. For that you need <h:inputHidden value="#{mailSender.controllerName}"/> instead.