Class Monitor

java.lang.Object

javax.management.NotificationBroadcasterSupport

javax.management.monitor.Monitor

All Implemented Interfaces:: MBeanRegistration, MonitorMBean, NotificationBroadcaster, NotificationEmitter

Direct Known Subclasses:: CounterMonitor, GaugeMonitor, StringMonitor

public abstract class Monitor extends NotificationBroadcasterSupport implements MonitorMBean, MBeanRegistration

Defines the part common to all monitor MBeans. A monitor MBean monitors values of an attribute common to a set of observed MBeans. The observed attribute is monitored at intervals specified by the granularity period. A gauge value (derived gauge) is derived from the values of the observed attribute.

Since:: 1.5

Field Summary

Modifier and Type	Field	Description
`protected int`	`alreadyNotified`	Deprecated. equivalent to `alreadyNotifieds`[0].
`protected int[]`	`alreadyNotifieds`	Selected monitor errors that have already been notified.
`protected static final int`	`capacityIncrement`	The amount by which the capacity of the monitor arrays are automatically incremented when their size becomes greater than their capacity.
`protected String`	`dbgTag`	Deprecated. No replacement.
`protected int`	`elementCount`	The number of valid components in the vector of observed objects.
`protected static final int`	`OBSERVED_ATTRIBUTE_ERROR_NOTIFIED`	Flag denoting that a notification has occurred after changing the observed attribute.
`protected static final int`	`OBSERVED_ATTRIBUTE_TYPE_ERROR_NOTIFIED`	Flag denoting that a notification has occurred after changing the observed object or the observed attribute.
`protected static final int`	`OBSERVED_OBJECT_ERROR_NOTIFIED`	Flag denoting that a notification has occurred after changing the observed object.
`protected static final int`	`RESET_FLAGS_ALREADY_NOTIFIED`	This flag is used to reset the `alreadyNotifieds` monitor attribute.
`protected static final int`	`RUNTIME_ERROR_NOTIFIED`	Flag denoting that a notification has occurred after changing the observed object or the observed attribute.
`protected MBeanServer`	`server`	Reference to the MBean server.

Constructor Summary

Constructor	Description
`Monitor()`	Constructor for subclasses to call.

Method Summary

Modifier and Type	Method	Description
`void`	`addObservedObject(ObjectName object)`	Adds the specified object in the set of observed MBeans, if this object is not already present.
`boolean`	`containsObservedObject(ObjectName object)`	Tests whether the specified object is in the set of observed MBeans.
`long`	`getGranularityPeriod()`	Gets the granularity period (in milliseconds).
`String`	`getObservedAttribute()`	Gets the attribute being observed.
`ObjectName`	`getObservedObject()`	Deprecated. As of JMX 1.2, replaced by `getObservedObjects()`
`ObjectName[]`	`getObservedObjects()`	Returns an array containing the objects being observed.
`boolean`	`isActive()`	Tests whether the monitor MBean is active.
`void`	`postDeregister()`	Allows the monitor MBean to perform any operations needed after having been unregistered by the MBean server.
`void`	`postRegister(Boolean registrationDone)`	Allows the monitor MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.
`void`	`preDeregister()`	Allows the monitor MBean to perform any operations it needs before being unregistered by the MBean server.
`ObjectName`	`preRegister(MBeanServer server, ObjectName name)`	Allows the monitor MBean to perform any operations it needs before being registered in the MBean server.
`void`	`removeObservedObject(ObjectName object)`	Removes the specified object from the set of observed MBeans.
`void`	`setGranularityPeriod(long period)`	Sets the granularity period (in milliseconds).
`void`	`setObservedAttribute(String attribute)`	Sets the attribute to observe.
`void`	`setObservedObject(ObjectName object)`	Deprecated. As of JMX 1.2, replaced by `addObservedObject(javax.management.ObjectName)`
`abstract void`	`start()`	Starts the monitor.
`abstract void`	`stop()`	Stops the monitor.

Methods declared in class javax.management.NotificationBroadcasterSupport

addNotificationListener, getNotificationInfo, handleNotification, removeNotificationListener, removeNotificationListener, sendNotification

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

capacityIncrement

protected static final int capacityIncrement

The amount by which the capacity of the monitor arrays are automatically incremented when their size becomes greater than their capacity.

See Also:

elementCount

protected int elementCount

The number of valid components in the vector of observed objects.

alreadyNotified

@Deprecated protected int alreadyNotified

Deprecated.

equivalent to alreadyNotifieds[0].

Monitor errors that have already been notified.

alreadyNotifieds

protected int[] alreadyNotifieds

Selected monitor errors that have already been notified.

Each element in this array corresponds to an observed object in the vector. It contains a bit mask of the flags OBSERVED_OBJECT_ERROR_NOTIFIED etc, indicating whether the corresponding notification has already been sent for the MBean being monitored.

server

protected MBeanServer server

Reference to the MBean server. This reference is null when the monitor MBean is not registered in an MBean server. This reference is initialized before the monitor MBean is registered in the MBean server.

See Also:

RESET_FLAGS_ALREADY_NOTIFIED

protected static final int RESET_FLAGS_ALREADY_NOTIFIED

This flag is used to reset the alreadyNotifieds monitor attribute.

See Also:

OBSERVED_OBJECT_ERROR_NOTIFIED

protected static final int OBSERVED_OBJECT_ERROR_NOTIFIED

Flag denoting that a notification has occurred after changing the observed object. This flag is used to check that the new observed object is registered in the MBean server at the time of the first notification.

See Also:

OBSERVED_ATTRIBUTE_ERROR_NOTIFIED

protected static final int OBSERVED_ATTRIBUTE_ERROR_NOTIFIED

Flag denoting that a notification has occurred after changing the observed attribute. This flag is used to check that the new observed attribute belongs to the observed object at the time of the first notification.

See Also:

OBSERVED_ATTRIBUTE_TYPE_ERROR_NOTIFIED

protected static final int OBSERVED_ATTRIBUTE_TYPE_ERROR_NOTIFIED

Flag denoting that a notification has occurred after changing the observed object or the observed attribute. This flag is used to check that the observed attribute type is correct (depending on the monitor in use) at the time of the first notification.

See Also:

RUNTIME_ERROR_NOTIFIED

protected static final int RUNTIME_ERROR_NOTIFIED

Flag denoting that a notification has occurred after changing the observed object or the observed attribute. This flag is used to notify any exception (except the cases described above) when trying to get the value of the observed attribute at the time of the first notification.

See Also:

dbgTag

@Deprecated protected String dbgTag

Deprecated.

No replacement.

This field is retained for compatibility but should not be referenced.

Constructor Details

Monitor

public Monitor()

Constructor for subclasses to call.

Method Details

preRegister

public ObjectName preRegister(MBeanServer server, ObjectName name) throws Exception

Allows the monitor MBean to perform any operations it needs before being registered in the MBean server.

Initializes the reference to the MBean server.

Specified by:: preRegister in interface MBeanRegistration
Parameters:: server - The MBean server in which the monitor MBean will be registered.; name - The object name of the monitor MBean.
Returns:: The name of the monitor MBean registered.
Throws:: Exception - if something goes wrong

postRegister

public void postRegister(Boolean registrationDone)

Allows the monitor MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.

Not used in this context.

Specified by:: postRegister in interface MBeanRegistration
Parameters:: registrationDone - Indicates whether or not the MBean has been successfully registered in the MBean server. The value false means that the registration phase has failed.

preDeregister

public void preDeregister() throws Exception

Allows the monitor MBean to perform any operations it needs before being unregistered by the MBean server.

Stops the monitor.

Specified by:: preDeregister in interface MBeanRegistration
Throws:: Exception - if something goes wrong

postDeregister

public void postDeregister()

Allows the monitor MBean to perform any operations needed after having been unregistered by the MBean server.

Not used in this context.

Specified by:: postDeregister in interface MBeanRegistration

start

public abstract void start()

Starts the monitor.

Specified by:: start in interface MonitorMBean

stop

public abstract void stop()

Stops the monitor.

Specified by:: stop in interface MonitorMBean

getObservedObject

@Deprecated public ObjectName getObservedObject()

Deprecated.

As of JMX 1.2, replaced by getObservedObjects()

Returns the object name of the first object in the set of observed MBeans, or null if there is no such object.

Specified by:

getObservedObject in interface MonitorMBean

Returns:

The object being observed.

See Also:

setObservedObject

@Deprecated public void setObservedObject(ObjectName object) throws IllegalArgumentException

Deprecated.

As of JMX 1.2, replaced by addObservedObject(javax.management.ObjectName)

Removes all objects from the set of observed objects, and then adds the specified object.

Specified by:

setObservedObject in interface MonitorMBean

Parameters:

object - The object to observe.

Throws:

IllegalArgumentException - The specified object is null.

See Also:

addObservedObject

public void addObservedObject(ObjectName object) throws IllegalArgumentException

Adds the specified object in the set of observed MBeans, if this object is not already present.

Specified by:: addObservedObject in interface MonitorMBean
Parameters:: object - The object to observe.
Throws:: IllegalArgumentException - The specified object is null.

removeObservedObject

public void removeObservedObject(ObjectName object)

Removes the specified object from the set of observed MBeans.

Specified by:: removeObservedObject in interface MonitorMBean
Parameters:: object - The object to remove.

containsObservedObject

public boolean containsObservedObject(ObjectName object)

Tests whether the specified object is in the set of observed MBeans.

Specified by:: containsObservedObject in interface MonitorMBean
Parameters:: object - The object to check.
Returns:: true if the specified object is present, false otherwise.

getObservedObjects

public ObjectName[] getObservedObjects()

Returns an array containing the objects being observed.

Specified by:: getObservedObjects in interface MonitorMBean
Returns:: The objects being observed.

getObservedAttribute

public String getObservedAttribute()

Gets the attribute being observed.
The observed attribute is not initialized by default (set to null).

Specified by:

getObservedAttribute in interface MonitorMBean

Returns:

The attribute being observed.

See Also:

setObservedAttribute

public void setObservedAttribute(String attribute) throws IllegalArgumentException

Sets the attribute to observe.
The observed attribute is not initialized by default (set to null).

Specified by:

setObservedAttribute in interface MonitorMBean

Parameters:

attribute - The attribute to observe.

Throws:

IllegalArgumentException - The specified attribute is null.

See Also:

getGranularityPeriod

public long getGranularityPeriod()

Gets the granularity period (in milliseconds).
The default value of the granularity period is 10 seconds.

Specified by:

getGranularityPeriod in interface MonitorMBean

Returns:

The granularity period value.

See Also:

setGranularityPeriod

public void setGranularityPeriod(long period) throws IllegalArgumentException

Sets the granularity period (in milliseconds).
The default value of the granularity period is 10 seconds.

Specified by:

setGranularityPeriod in interface MonitorMBean

Parameters:

period - The granularity period value.

Throws:

IllegalArgumentException - The granularity period is less than or equal to zero.

See Also:

isActive

public boolean isActive()

Tests whether the monitor MBean is active. A monitor MBean is marked active when the start method is called. It becomes inactive when the stop method is called.

Specified by:: isActive in interface MonitorMBean
Returns:: true if the monitor MBean is active, false otherwise.

© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.management/javax/management/monitor/Monitor.html