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MemoryNotificationInfo.javaAPI DocJava SE 5 API8748Fri Aug 26 14:57:06 BST 2005java.lang.management

MemoryNotificationInfo

public class MemoryNotificationInfo extends Object
The information about a memory notification.

A memory notification is emitted by {@link 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 {@link MemoryPoolMXBean#getUsageThresholdCount usage threshold count}. For collection threshold notifications, this count will be the {@link MemoryPoolMXBean#getCollectionUsageThresholdCount collection usage threshold count}.

A {@link CompositeData CompositeData} representing the MemoryNotificationInfo object is stored in the {@link javax.management.Notification#setUserData user data} of a {@link javax.management.Notification notification}. The {@link #from 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 {@link #MEMORY_THRESHOLD_EXCEEDED 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 {@link #MEMORY_COLLECTION_THRESHOLD_EXCEEDED 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.
author
Mandy Chung
version
1.6, 04/18/04
since
1.5

Fields Summary
private final String
poolName
private final MemoryUsage
usage
private final long
count
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 {@link 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.
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 {@link MemoryMXBean}. The value of this notification type is java.management.memory.collection.threshold.exceeded.
Constructors Summary
public MemoryNotificationInfo(String poolName, MemoryUsage usage, long count)
Constructs a MemoryNotificationInfo object.

param
poolName The name of the memory pool which triggers this notification.
param
usage Memory usage of the memory pool.
param
count The threshold crossing count.


                                       
      
                                   
                                    
        if (poolName == null) {
            throw new NullPointerException("Null poolName");
        }
        if (usage == null) {
            throw new NullPointerException("Null usage");
        }

        this.poolName = poolName;
        this.usage = usage;
        this.count = count;
MemoryNotificationInfo(CompositeData cd)

        MemoryNotifInfoCompositeData.validateCompositeData(cd);

        this.poolName = MemoryNotifInfoCompositeData.getPoolName(cd);
        this.usage = MemoryNotifInfoCompositeData.getUsage(cd);
        this.count = MemoryNotifInfoCompositeData.getCount(cd);
Methods Summary
public static java.lang.management.MemoryNotificationInfofrom(javax.management.openmbean.CompositeData cd)
Returns a MemoryNotificationInfo object represented by the given CompositeData. The given CompositeData must contain the following attributes:
Attribute Name Type
poolName java.lang.String
usage javax.management.openmbean.CompositeData
count java.lang.Long

param
cd CompositeData representing a MemoryNotificationInfo
throws
IllegalArgumentException if cd does not represent a MemoryNotificationInfo object.
return
a MemoryNotificationInfo object represented by cd if cd is not null; null otherwise.

        if (cd == null) {
            return null;
        }

        if (cd instanceof MemoryNotifInfoCompositeData) {
            return ((MemoryNotifInfoCompositeData) cd).getMemoryNotifInfo();
        } else {
            return new MemoryNotificationInfo(cd);
        }
public longgetCount()
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 {@link MemoryPoolMXBean#getUsageThresholdCount threshold count}. For collection threshold notifications, this count will be the {@link MemoryPoolMXBean#getCollectionUsageThresholdCount collection usage threshold count}.

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

        return count;
public java.lang.StringgetPoolName()
Returns the name of the memory pool that triggers this notification. The memory pool usage has crossed a threshold.

return
the name of the memory pool that triggers this notification.

        return poolName;
public java.lang.management.MemoryUsagegetUsage()
Returns the memory usage of the memory pool when this notification was constructed.

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

        return usage;