com.github.f4b6a3.uuid.nodeid

Class DefaultNodeIdentifierStrategy

java.lang.Object

com.github.f4b6a3.uuid.nodeid.DefaultNodeIdentifierStrategy

All Implemented Interfaces:

NodeIdentifierStrategy

public class DefaultNodeIdentifierStrategy
extends Object
implements NodeIdentifierStrategy

Field Summary

Fields

Modifier and Type	Field and Description
protected long	nodeIdentifier
protected Random	random

Constructor Summary

Constructors

Constructor and Description
DefaultNodeIdentifierStrategy()

Method Summary

Modifier and Type	Method and Description
long	getNodeIdentifier() Return a random node identifier.
protected long	getRandomMulticastNodeIdentifier() Return a random generated node identifier.

Methods inherited from class java.lang.Object

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

Field Detail

nodeIdentifier

protected long nodeIdentifier

random

protected Random random

Constructor Detail

DefaultNodeIdentifierStrategy

public DefaultNodeIdentifierStrategy()

Method Detail

getNodeIdentifier

public long getNodeIdentifier()

Return a random node identifier. It uses SecureRandom to generate 'cryptographic quality random number'. The first generated number is returned for all calls. ### RFC-4122 - 4.1.6. Node (2a) For systems with no IEEE address, a randomly or pseudo-randomly generated value may be used; see Section 4.5. The multicast bit must be set in such addresses, in order that they will never conflict with addresses obtained from network cards. ### RFC-4122 - 4.5. Node IDs that Do Not Identify the Host (1b) This section describes how to generate a version 1 UUID if an IEEE 802 address is not available, or its use is not desired. (2b) One approach is to contact the IEEE and get a separate block of addresses. At the time of writing, the application could be found at http://standards.ieee.org/regauth/oui/pilot-ind.html, and the cost was US$550. (3b) A better solution is to obtain a 47-bit cryptographic quality random number and use it as the low 47 bits of the node ID, with the least significant bit of the first octet of the node ID set to one. This bit is the unicast/multicast bit, which will never be set in IEEE 802 addresses obtained from network cards. Hence, there can never be a conflict between UUIDs generated by machines with and without network cards. (Recall that the IEEE 802 spec talks about transmission order, which is the opposite of the in-memory representation that is discussed in this document.)

Specified by:

getNodeIdentifier in interface NodeIdentifierStrategy

Returns:

a node identifier

getRandomMulticastNodeIdentifier

protected long getRandomMulticastNodeIdentifier()

Return a random generated node identifier. getNodeIdentifier()

Returns:

a random multicast node identifier