The field allows the specification of event invocation options. They could be a comma delimited list, like "immediate, postback, ajax". What options are available, and the default, could depend on the platform involved.

Some common call types are defined below:

<blank>           Default: processed through the controller
direct:             navigation to pages, without the use of handler

immediate:      instruction to skip the controller services

ajax:                Use the AJAX call mechanism

auto-postback:  Page round trip event, usually allowing getting the attention of component listeners and then representing the page.

ws:                   Call to a web service

Multiple call types might be applicable, whereas some options as mutually exclusive.

The set of standard call types are as defined above. In the discussion below, JSF specific points are the subjects.

immediate: In general terms, this is an indicator to skip some of the controller services, bringing up the event handling immediately. In JSF terms it indicates that notifications should be delivered to interested listeners and actions immediately (that is, during Apply Request Values phase) rather than waiting until Invoke Application phase.

This translates to the immediate attribute of the component having a true value, false being the default. This is pertains to command type components only.

ajax: In depth discussion on the implication this is discussed in the AJAX section.

auto-postback: All action events would lead to postback, implies that events command server side effects immediately following the event. This is however not the case for non-command events. For example, the value change events do not invoke post back, the changes are registered but the handler would only be invoked whenever a subsequent action event commands the controller attention.

When auto-postback is specified for an event, the implication is that there is server invocation with the occurrence of such event. JSF does not provide neither flag nor method of depicting auto-postback. The method for achieving this is through scripting, by providing a client event handler along with the server handler specification. The client handler would simply do a submit using script, contending with the usual issue of obtaining the identity of the enclosing form at runtime. Two common methods for achieving this is shown below; the first assumes that there is only one form, or else the form of interest is the first.

	onchange= "document.forms[0].submit();"

	onchange= "this.form.submit();"