Java Reference
In-Depth Information
However, more often than not, the
render
attribute is likely to be associated with an
event
attribute. In the following example, an output component is displayed when the
button component is clicked.
<h:commandButton id="submit" value="Submit">
<f:ajax event="click" execute="userNo" render="result"/>
</h:commandButton>
<h:outputText id="result" value="#{userNumberBean.response}"/>
Note
Behind the scenes, once again the
jsf.ajax.request()
method
handles the response. It registers a response-handling callback when the
original request is created. When the response is sent back to the client,
the callback is invoked. This callback automatically updates the client-
side DOM to reflect the rendered response.
Ajax Request Lifecycle
An Ajax request varies from other typical JavaServer Faces requests, and its processing is
also handled differently by the JavaServer Faces lifecycle.
As described in “
Partial Processing and Partial Rendering
” on page
56
,
when an Ajax
request is received, the state associated with that request is captured by the
javax.faces.context.PartialViewContext
. This object provides access to
information such as which components are targeted for processing/rendering. The
pro-
cessPartial
method of
PartialViewContext
uses this information to perform
partial component tree processing and rendering.
The
execute
attribute of the
f:ajax
tag identifies which segments of the server side
component tree should be processed. Because components can be uniquely identified in
the JavaServer Faces component tree, it is easy to identify and process a single compon-
ent, a few components, or a whole tree. This is made possible by the
visitTree
method
of the
javax.faces.component.UIComponent
class. The identified components
then run through the JavaServer Faces request lifecycle phases.
Similar to the
execute
attribute, the
render
attribute identifies which segments of the
JavaServer Faces component tree need to be rendered during the render response phase.
