actionRef="action to be triggered"
commandName="used for actionlistener to determined where to go"
<ui:Component>
insert into component tree, ignore outside content
<ui:fragment>
insert into tree, not ignore outside content
<ui:Composition>
not created in component tree, ignore outside conten
<ui:decorate> - need template.xml
not create in tree, not ignore outside content
<ui:insert> specify a template those parts can be replace by <ui:define> tag
If action and listener are all added to button, the listener will be triggered first, then the action.
@see UICommand#broadcast(ActionEvent event)
If there is onClick attached to button, onClick will be triggered first.