<h:commandButton id="submit" value="Submit">
<f:ajax event="click" />
</h:commandButton>
<h:outputText id="result" value="#{userNumberBean.response}" />
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Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial |
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To activate Ajax functionality, the web application must create an Ajax request and send it to the server. The server then processes the request.
The application uses the attributes of the f:ajax tag listed in
Table 13-1 to create the Ajax request. The
following sections explain the process of creating and sending an Ajax
request using some of these attributes.
Note: Behind the scenes, the |
The following topics are addressed here:
The event attribute defines the event that triggers the Ajax action.
Some of the possible values for this attribute are click, keyup,
mouseover, focus, and blur.
If not specified, a default event based on the parent component will be
applied. The default event is action for
javax.faces.component.ActionSource components, such as a
commandButton, and valueChange for
javax.faces.component.EditableValueHolder components, such as
inputText. In the following example, an Ajax tag is associated with
the button component, and the event that triggers the Ajax action is a
mouse click:
<h:commandButton id="submit" value="Submit">
<f:ajax event="click" />
</h:commandButton>
<h:outputText id="result" value="#{userNumberBean.response}" />
Note: You may have noticed that the listed events are very similar to
JavaScript events. In fact, they are based on JavaScript events, but do
not have the |
For a command button, the default event is click, so you do not
actually need to specify event="click" to obtain the desired behavior.
The execute attribute defines the component or components to be
executed on the server. The component is identified by its id
attribute. You can specify more than one executable component. If more
than one component is to be executed, specify a space-delimited list of
components.
When a component is executed, it participates in all phases of the request-processing lifecycle except the Render Response phase.
The execute attribute value can also be a keyword, such as @all,
@none, @this, or @form. The default value is @this, which refers
to the component within which the f:ajax tag is nested.
The following code specifies that the h:inputText component with the
id value of userNo should be executed when the button is clicked:
<h:inputText id="userNo"
title="Type a number from 0 to 10:"
value="#{userNumberBean.userNumber}">
...
</h:inputText>
<h:commandButton id="submit" value="Submit">
<f:ajax event="click" execute="userNo" />
</h:commandButton>
The immediate attribute indicates whether user inputs are to be
processed early in the application lifecycle or later. If the attribute
is set to true, events generated from this component are broadcast
during the Apply Request Values phase. Otherwise, the events will be
broadcast during the Invoke Application phase.
If not defined, the default value of this attribute is false.
The listener attribute refers to a method expression that is executed
on the server side in response to an Ajax action on the client. The
listener’s javax.faces.event.AjaxBehaviorListener.processAjaxBehavior
method is called once during the Invoke Application phase of the
lifecycle. In the following code from the reservation example
application (see The reservation
Example Application), a listener attribute is defined by an f:ajax
tag, which refers to a method from the bean:
<f:ajax event="change" render="total"
listener="#{reservationBean.calculateTotal}"/>
Whenever either the price or the number of tickets ordered changes, the
calculateTotal method of ReservationBean recalculates the total cost
of the tickets and displays it in the output component named total.
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