org.aredis.io

Class ClassDescriptors

java.lang.Object

org.aredis.io.ClassDescriptorsInfo

org.aredis.io.ClassDescriptors

All Implemented Interfaces:

Serializable, Cloneable

public class ClassDescriptors
extends ClassDescriptorsInfo

Holds Class Descriptors in an internal array.

This is an important class for OPTI_JAVA_HANDLER. However this and the other io classes are not tied to any aredis specific stuff. Also this is not to be used directly but is used by ClassDescriptorStorage, OptiObjectInputStream and OptiObjectOutputStream.

This is for maintaining a central array of Class Descriptors used in Object Serialization and de-serialization. The class descriptors in the serialized data is only an index into this array.

The array is stored and retrieved by an implementation of ClassDescriptorStorage.

Whenever ClassDescriptors is created or fetched from the store it is read only. It can be made writable by cloning it if a new class descriptor is to be added. Then a save attempt is to be made via ClassDescriptorStorage which should be based on optimistic locking (Dirty Check) using the versionNo. If the save fails a retry should be done.

Author:

Suresh

See Also:

Serialized Form

Field Summary

Fields inherited from class org.aredis.io.ClassDescriptorsInfo

specVersion, versionNo

Constructor Summary

Constructors

Constructor and Description
ClassDescriptors() Creates a read only ClassDescriptors.

Method Summary

Methods

Modifier and Type	Method and Description
ClassDescriptors	clone() Clones the current descriptor.
ClassDescriptors	clone(boolean pisWritable) Clones the current descriptor.
void	copyMetaInfoTo(ClassDescriptors cld) Copies meta info like written class descriptors and lastUseTime to another ClassDescriptors.
ClassDescriptorsInfo	createInfo() Creates an info Object containing the versionNo.
ObjectStreamClass	getDescriptor(int index) Gets the ObjectStreamClass at the given index.
boolean	isWritable() Returns if this ClassDescriptors is writable.
int	removeOldDescriptors(long lastUseTime) Removes old descriptors not used since the passed lastUseTime.
boolean	requiresTimingUpdate(long updateInterval) Checks whether the use time fetched from store and current use time differs by more than the given updateInterval for any of the descriptors.

Methods inherited from class org.aredis.io.ClassDescriptorsInfo

getSpecVersion, getVersionNo

Methods inherited from class java.lang.Object

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

Constructor Detail

ClassDescriptors

public ClassDescriptors()

Creates a read only ClassDescriptors.

Method Detail

clone

public ClassDescriptors clone(boolean pisWritable)
                       throws CloneNotSupportedException

Clones the current descriptor.

Parameters:

pisWritable - Whether new descriptor should be writable. The version number of the clone is incremented if this is not writable and the cloned one is writable.

Returns:

Cloned Object

Throws:

CloneNotSupportedException

clone

public ClassDescriptors clone()
                       throws CloneNotSupportedException

Clones the current descriptor. Equivalent to clone(true).

Overrides:

clone in class Object

Throws:

CloneNotSupportedException

createInfo

public ClassDescriptorsInfo createInfo()

Creates an info Object containing the versionNo. This is currently not used.

Returns:

An Info Object

copyMetaInfoTo

public void copyMetaInfoTo(ClassDescriptors cld)

Copies meta info like written class descriptors and lastUseTime to another ClassDescriptors. This is used when refreshing the jvm copy of ClassDescriptors from the store. The meta info from the current one is copied to the new one got from store.

Parameters:

cld - Descriptors Object to copy meta info to

getDescriptor

public ObjectStreamClass getDescriptor(int index)

Gets the ObjectStreamClass at the given index.

Parameters:

index - index

Returns:

Class Descriptor at given index

removeOldDescriptors

public int removeOldDescriptors(long lastUseTime)

Removes old descriptors not used since the passed lastUseTime. This gets called via a cron but the remove feature is not used as it involves removing ClassDescriptors and therefore requires some basic testing. Currently lastUseTime is passed as 100 years ago by the cron.

Parameters:

lastUseTime - Last Use Milliseconds time

Returns:

Number of descriptors removed

requiresTimingUpdate

public boolean requiresTimingUpdate(long updateInterval)

Checks whether the use time fetched from store and current use time differs by more than the given updateInterval for any of the descriptors. A cron calls this with a day as the interval.

Parameters:

updateInterval - Update Interval in milliseconds

Returns:

true if an update of the current descriptors to store for storing the last use times is required as per the passed update Interval

isWritable

public boolean isWritable()

Returns if this ClassDescriptors is writable.

Returns:

isWritable flag