FULL PRODUCT VERSION :
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Client VM (build 1.5.0-b64, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
It seems there is an inconsistency between the JMX1.2 spec and the javadoc/jdk5 code:

Spec says:

"jmx.monitor.error.type - Sent when the object instance of the observed attribute value is null or not of the appropriate type for the given monitor...."

Javadoc for MonitorNotification says:

    /**
     * Notification type denoting that the type of the observed attribute is not correct.
     * This notification is fired by all kinds of monitors.
     * <BR>The value of this notification type is <CODE>jmx.monitor.error.type</CODE>.
     */
    public static final String OBSERVED_ATTRIBUTE_TYPE_ERROR = "jmx.monitor.error.type";

The StringMonitor of Jdk5 does nothing when a monitored String attribute has a "null" value. If the spec is correct, StringMonitor should emit a "jmx.monitor.error.type" notification (once) when a "null" value is detected. Otherwise, the spec should be corrected.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
create a StringMonitor and point it to an MBean with a String attribute having an initial null value.


REPRODUCIBILITY :
This bug can be reproduced always.