Java Reference
In-Depth Information
bookId);
}
When the JavaServer Faces implementation calls this method, it passes in an
Ac-
tionEvent
object that represents the event generated by clicking on the image map.
Next, it casts it to an
AreaSelectedEvent
object (see
tut-install
/examples/
case-studies/dukes-bookstore/src/java/dukesbookstore/
listeners/AreaSelectedEvent.java
). Then this method gets the
MapCom-
ponent
associated with the event. It then gets the value of the
MapComponent
object's
current
attribute, which indicates the currently selected area. The method then uses the
value of the
current
attribute to get the topic's ID value from a
HashMap
object, which
is constructed elsewhere in the
MapBookChangeListener
class. Finally the method
places the ID obtained from the
HashMap
object into the session map for the applica-
tion.
In addition to the method that processes the event, you need the event class itself. This
class is very simple to write: You have it extend
ActionEvent
and provide a construct-
or that takes the component on which the event is queued and a method that returns the
component.
Here is the
AreaSelectedEvent
class used with the image map:
public class AreaSelectedEvent extends ActionEvent {
public AreaSelectedEvent(MapComponent map) {
super(map);
}
public MapComponent getMapComponent() {
return ((MapComponent) getComponent());
}
}
As explained in the section “
Creating Custom Component Classes
”
on page
106
,
in order
for
MapComponent
to fire events in the first place, it must implement
ActionSource
.
Because
MapComponent
extends
UICommand
, it also implements
ActionSource
.
Defining the Custom Component Tag in a Tag Library Descriptor
To use a custom tag, you declare it in a Tag Library Descriptor (TLD). The TLD file
defines how the custom tag is used in a JavaServer Faces page. The web container uses the
TLD to validate the tag. The set of tags that are part of the HTML render kit are defined
