com.fasterxml.uuid.impl

Class TimeBasedEpochRandomGenerator

java.lang.Object

com.fasterxml.uuid.UUIDGenerator

com.fasterxml.uuid.NoArgGenerator

com.fasterxml.uuid.impl.TimeBasedEpochRandomGenerator

public class TimeBasedEpochRandomGenerator
extends NoArgGenerator

Implementation of UUID generator that uses time/location based generation method field from the Unix Epoch timestamp source - the number of milliseconds seconds since midnight 1 Jan 1970 UTC, leap seconds excluded. This is usually referred to as "Version 7". In addition to that random part is regenerated for every new UUID. This removes possibilities to have almost similar UUID, when calls to generate are made within same millisecond.

As all JUG provided implementations, this generator is fully thread-safe. Additionally it can also be made externally synchronized with other instances (even ones running on other JVMs); to do this, use FileBasedTimestampSynchronizer (or equivalent).

Since:

5.0

Field Summary

Fields

Modifier and Type	Field and Description
protected UUIDClock	_clock Underlying UUIDClock used for accessing current time, to use for generation.
protected Random	_random Random number generator that this generator uses.

Constructor Summary

Constructors

Constructor and Description
TimeBasedEpochRandomGenerator(Random rnd)
TimeBasedEpochRandomGenerator(Random rnd, UUIDClock clock)

Method Summary

Modifier and Type	Method and Description
UUID	construct(long rawTimestamp) Method that will construct actual UUID instance for given unix epoch timestamp: called by generate() but may alternatively be called directly to construct an instance with known timestamp.
UUID	generate() Method for generating a UUID.
UUIDType	getType() Accessor for determining type of UUIDs (version) that this generator instance will produce.

Methods inherited from class com.fasterxml.uuid.UUIDGenerator

_toInt, _toLong, _toShort

Methods inherited from class java.lang.Object

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

Field Detail

_random

protected final Random _random

Random number generator that this generator uses.

_clock

protected final UUIDClock _clock

Underlying UUIDClock used for accessing current time, to use for generation.

Constructor Detail

TimeBasedEpochRandomGenerator

public TimeBasedEpochRandomGenerator(Random rnd)

Parameters:

rnd - Random number generator to use for generating UUIDs; if null, shared default generator is used. Note that it is strongly recommend to use a good (pseudo) random number generator; for example, JDK's SecureRandom.

TimeBasedEpochRandomGenerator

public TimeBasedEpochRandomGenerator(Random rnd,
                                     UUIDClock clock)

Parameters:

rnd - Random number generator to use for generating UUIDs; if null, shared default generator is used. Note that it is strongly recommend to use a good (pseudo) random number generator; for example, JDK's SecureRandom.

clock - clock Object used for accessing current time to use for generation

Method Detail

getType

public UUIDType getType()

Description copied from class: UUIDGenerator

Accessor for determining type of UUIDs (version) that this generator instance will produce.

Specified by:

getType in class UUIDGenerator

generate

public UUID generate()

Description copied from class: NoArgGenerator

Method for generating a UUID.

Specified by:

generate in class NoArgGenerator

Returns:

Newly generated UUID

construct

public UUID construct(long rawTimestamp)

Method that will construct actual UUID instance for given unix epoch timestamp: called by generate() but may alternatively be called directly to construct an instance with known timestamp. NOTE: calling this method directly produces somewhat distinct UUIDs as "entropy" value is still generated as necessary to avoid producing same UUID even if same timestamp is being passed.

Parameters:

rawTimestamp - unix epoch millis

Returns:

unix epoch time based UUID