org.apache.derby.impl.services.uuid
Class BasicUUIDFactory

java.lang.Object
  org.apache.derby.impl.services.uuid.BasicUUIDFactory

All Implemented Interfaces:

UUIDFactory

public final class BasicUUIDFactory
extends java.lang.Object
implements UUIDFactory

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

private long	currentValue
private static long	INITIAL_VALUE
private long	majorId
private static long	MODULUS
private static long	MULTIPLIER
private static long	STEP
private long	timemillis

Constructor Summary

BasicUUIDFactory()

Method Summary

private void	bumpMajor()
UUID	createUUID() Generate a new UUID.
UUID	recreateUUID(java.lang.String uuidstring) Recreate a UUID previously generated UUID value.
private void	resetCounters()

Methods inherited from class java.lang.Object

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

Field Detail

majorId

private long majorId

timemillis

private long timemillis

MODULUS

private static final long MODULUS

See Also:

Constant Field Values

MULTIPLIER

private static final long MULTIPLIER

See Also:

Constant Field Values

STEP

private static final long STEP

See Also:

Constant Field Values

INITIAL_VALUE

private static final long INITIAL_VALUE

See Also:

Constant Field Values

currentValue

private long currentValue

Constructor Detail

BasicUUIDFactory

public BasicUUIDFactory()

Method Detail

createUUID

public UUID createUUID()

Generate a new UUID.

Specified by:

createUUID in interface UUIDFactory

Returns:

The UUID.

See Also:

UUIDFactory.createUUID()

recreateUUID

public UUID recreateUUID(java.lang.String uuidstring)

Recreate a UUID previously generated UUID value.

Specified by:

recreateUUID in interface UUIDFactory

Returns:

The UUID.

See Also:

UUIDFactory.recreateUUID(java.lang.String)

bumpMajor

private void bumpMajor()

resetCounters

private void resetCounters()