Module java.management

Package java.lang.management

Class MemoryNotificationInfo

java.lang.Object

java.lang.management.MemoryNotificationInfo

public class MemoryNotificationInfo
extends Object

The information about a memory notification.

A memory notification is emitted by MemoryMXBean when the Java virtual machine detects that the memory usage of a memory pool is exceeding a threshold value. The notification emitted will contain the memory notification information about the detected condition:

• The name of the memory pool.
• The memory usage of the memory pool when the notification was constructed.
• The number of times that the memory usage has crossed a threshold when the notification was constructed. For usage threshold notifications, this count will be the usage threshold count. For collection threshold notifications, this count will be the collection usage threshold count.

A CompositeData representing the MemoryNotificationInfo object is stored in the user data of a notification. The from method is provided to convert from a CompositeData to a MemoryNotificationInfo object. For example:

      Notification notif;

      // receive the notification emitted by MemoryMXBean and set to notif
      ...

      String notifType = notif.getType();
      if (notifType.equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED) ||
          notifType.equals(MemoryNotificationInfo.MEMORY_COLLECTION_THRESHOLD_EXCEEDED)) {
          // retrieve the memory notification information
          CompositeData cd = (CompositeData) notif.getUserData();
          MemoryNotificationInfo info = MemoryNotificationInfo.from(cd);
          ....
      }
 

The types of notifications emitted by MemoryMXBean are:

• A usage threshold exceeded notification.
  This notification will be emitted when the memory usage of a memory pool is increased and has reached or exceeded its usage threshold value. Subsequent crossing of the usage threshold value does not cause further notification until the memory usage has returned to become less than the usage threshold value.
• A collection usage threshold exceeded notification.
  This notification will be emitted when the memory usage of a memory pool is greater than or equal to its collection usage threshold after the Java virtual machine has expended effort in recycling unused objects in that memory pool.

Since:

1.5

Field Summary

Fields

Modifier and Type	Field	Description
static String	MEMORY_COLLECTION_THRESHOLD_EXCEEDED	Notification type denoting that the memory usage of a memory pool is greater than or equal to its collection usage threshold after the Java virtual machine has expended effort in recycling unused objects in that memory pool.
static String	MEMORY_THRESHOLD_EXCEEDED	Notification type denoting that the memory usage of a memory pool has reached or exceeded its usage threshold value.

Constructor Summary

Constructors

Constructor	Description
MemoryNotificationInfo(String poolName, MemoryUsage usage, long count)	Constructs a MemoryNotificationInfo object.

Method Summary

Modifier and Type	Method	Description
static MemoryNotificationInfo	from(CompositeData cd)	Returns a MemoryNotificationInfo object represented by the given CompositeData.
long	getCount()	Returns the number of times that the memory usage has crossed a threshold when the notification was constructed.
String	getPoolName()	Returns the name of the memory pool that triggers this notification.
MemoryUsage	getUsage()	Returns the memory usage of the memory pool when this notification was constructed.

Methods declared in class java.lang.Object

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

Field Details

MEMORY_THRESHOLD_EXCEEDED

public static final String MEMORY_THRESHOLD_EXCEEDED

Notification type denoting that the memory usage of a memory pool has reached or exceeded its usage threshold value. This notification is emitted by MemoryMXBean. Subsequent crossing of the usage threshold value does not cause further notification until the memory usage has returned to become less than the usage threshold value. The value of this notification type is java.management.memory.threshold.exceeded.

See Also:

Constant Field Values

MEMORY_COLLECTION_THRESHOLD_EXCEEDED

public static final String MEMORY_COLLECTION_THRESHOLD_EXCEEDED

Notification type denoting that the memory usage of a memory pool is greater than or equal to its collection usage threshold after the Java virtual machine has expended effort in recycling unused objects in that memory pool. This notification is emitted by MemoryMXBean. The value of this notification type is java.management.memory.collection.threshold.exceeded.

See Also:

Constant Field Values

Constructor Details

MemoryNotificationInfo

public MemoryNotificationInfo(String poolName, MemoryUsage usage, long count)

Constructs a MemoryNotificationInfo object.

Parameters:

poolName - The name of the memory pool which triggers this notification.

usage - Memory usage of the memory pool.

count - The threshold crossing count.

Method Details

getPoolName

public String getPoolName()

Returns the name of the memory pool that triggers this notification. The memory pool usage has crossed a threshold.

Returns:

the name of the memory pool that triggers this notification.

getUsage

public MemoryUsage getUsage()

Returns the memory usage of the memory pool when this notification was constructed.

Returns:

the memory usage of the memory pool when this notification was constructed.

getCount

public long getCount()

Returns the number of times that the memory usage has crossed a threshold when the notification was constructed. For usage threshold notifications, this count will be the threshold count. For collection threshold notifications, this count will be the collection usage threshold count.

Returns:

the number of times that the memory usage has crossed a threshold when the notification was constructed.

from

public static MemoryNotificationInfo from(CompositeData cd)

Returns a MemoryNotificationInfo object represented by the given CompositeData. The given CompositeData must contain the following attributes:

The attributes and the types the given CompositeData contains

Attribute Name	Type
poolName	java.lang.String
usage	javax.management.openmbean.CompositeData
count	java.lang.Long

Parameters:

cd - CompositeData representing a MemoryNotificationInfo

Returns:

a MemoryNotificationInfo object represented by cd if cd is not null; null otherwise.

Throws:

IllegalArgumentException - if cd does not represent a MemoryNotificationInfo object.