Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.impl.services.uuid.BasicUUIDFactory

A hack implementation of something similar to a DCE UUID generator. Generates unique 128-bit numbers based on the current machine's internet address, the current time, and a sequence number. This implementation should be made to conform to the DCE specification. ("DEC/HP, Network Computing Architecture, Remote Procedure Call Runtime Extensions Specification, version OSF TX1.0.11," Steven Miller, July 23, 1992. This is part of the OSF DCE Documentation. Chapter 10 describes the UUID generation algorithm.)

Some known deficiencies:

Rather than using the 48-bit hardware network address, it uses the 32-bit IP address. IP addresses are not guaranteed to be unique.
There is no provision for generating a suitably unique number if no IP address is available.
Two processes running on this machine which start their respective UUID services within a millisecond of one another may generate duplicate UUIDS.

However, the intention is that UUIDs generated from this class will be unique with respect to UUIDs generated by other DCE UUID generators.

Field Summary

Modifier and Type	Field and Description
private long	currentValue
private static final long	INITIAL_VALUE
private long	majorId
private static final long	MODULUS
private static final long	MULTIPLIER
private static final long	STEP
private long	timemillis

Constructor Summary

Access	Constructor and Description
public	BasicUUIDFactory()

Method Summary

Modifier and Type	Method and Description
private void	bumpMajor()
public synchronized UUID	createUUID() Implements org.apache.derby.iapi.services.uuid.UUIDFactory.createUUID. Generate a new UUID.
private static ModuleFactory	getMonitor() Must be private so that user code can't call this entry point.
public UUID	recreateUUID(String A UUID as a string uuidstring) Implements org.apache.derby.iapi.services.uuid.UUIDFactory.recreateUUID. Recreate a UUID previously generated UUID value.
private void	resetCounters()

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

currentValue	back to summary
private long currentValue

INITIAL_VALUE	back to summary
private static final long INITIAL_VALUE

majorId	back to summary
private long majorId

MODULUS	back to summary
private static final long MODULUS

MULTIPLIER	back to summary
private static final long MULTIPLIER

STEP	back to summary
private static final long STEP

timemillis	back to summary
private long timemillis

Constructor Detail

BasicUUIDFactory	back to summary
public BasicUUIDFactory()

Method Detail

bumpMajor	back to summary
private void bumpMajor()

createUUID back to summary

createUUID	back to summary
public synchronized UUID createUUID() Implements org.apache.derby.iapi.services.uuid.UUIDFactory.createUUID. Generate a new UUID. Returns:UUID Doc from org.apache.derby.iapi.services.uuid.UUIDFactory.createUUID. The UUID. See Also `UUIDFactory#createUUID`

public synchronized UUID createUUID()

Implements org.apache.derby.iapi.services.uuid.UUIDFactory.createUUID.

Generate a new UUID.

Returns:UUID

Doc from org.apache.derby.iapi.services.uuid.UUIDFactory.createUUID.

The UUID.

See Also

UUIDFactory#createUUID

getMonitor	back to summary
private static ModuleFactory getMonitor() Must be private so that user code can't call this entry point.

recreateUUID back to summary

recreateUUID	back to summary
public UUID recreateUUID(String uuidstring) Implements org.apache.derby.iapi.services.uuid.UUIDFactory.recreateUUID. Recreate a UUID previously generated UUID value. Parameters uuidstring:String Doc from org.apache.derby.iapi.services.uuid.UUIDFactory.recreateUUID. A UUID as a string Returns:UUID Doc from org.apache.derby.iapi.services.uuid.UUIDFactory.recreateUUID. The UUID. See Also `UUIDFactory#recreateUUID`

public UUID recreateUUID(String uuidstring)

Implements org.apache.derby.iapi.services.uuid.UUIDFactory.recreateUUID.

Recreate a UUID previously generated UUID value.

Parameters

uuidstring:String

Doc from org.apache.derby.iapi.services.uuid.UUIDFactory.recreateUUID.

A UUID as a string

Returns:UUID