Java Reference
In-Depth Information
B
You change the declaration of the
HelloWorld
class by extending the
Notifica-
tionBroadcasterSupport
class. This super class provides the MBean with meth-
ods that allow other objects to register as notification listeners and allow the
MBean to send notifications. The super class implements the
javax.manage-
ment.NotificationBroadcaster
interface examined after this code discussion.
For this example, you are sending only basic notifications. At this step in the
code, you create a
Notification
object with the constructor
public Notification(java.lang.String type, java.lang.Object source,
long sequenceNumber,long timeStamp,
java.lang.String message
)
The parameters of this constructor are listed in table 2.4.
C
Table 2.4
The
Notification
constructor parameters
Parameter
Description
java.lang.String
type
Dot-separated
String
value used to identify the notification. Used as
a short description of the purpose and meaning for the notification.
java.lang.Object
source
The MBean that generated this notification. This will be either the
object reference or the
ObjectName
of an MBean.
A number that identifies this notification in a possible sequence of
notifications.
long sequenceNumber
A timestamp of the creation of the notification.
long timestamp
java.lang.String
message
A
String
value containing a message from the notification source.
D
By extending the
NotificationBroadcasterSupport
class, you not only gain the
implementation of the
NotificationBroadcaster
interface, but also inherit the
sendNotification()
method. Your
HelloWorld
MBean can use this convenience
method when it needs to send a notification, and the super class will send it to all
appropriate listeners. Appropriate listeners are those that have registered with
the MBean and whose filter object accepts the particular type of notification.
Examination of the NotificationBroadcaster interface
The previous example used the
NotificationBroadcasterSupport
class. This
class provides subclasses with an implementation of the
NotificationBroad-
caster
interface. The super class implements the
NotificationBroadcaster
interface shown next:
public interface NotificationBroadcaster
{
public void addNotificationListener(
NotificationListener listener,
