Package com.github.f4b6a3.uuid.strategy.nodeid

Class DefaultNodeIdentifierStrategy

  • All Implemented Interfaces:
    NodeIdentifierStrategy
    public class DefaultNodeIdentifierStrategy
extends Object
implements NodeIdentifierStrategy
    Strategy that always provides the same node identifier. By default it provides a random node identifier. A preferred node identifier may be passed by system property or environment variable. The default node identifier is replaced with the preferred one. It uses SecureRandom by default to generate 'cryptographic quality random number'. The first generated number is returned for all calls.

    • Field Detail

      • nodeIdentifier

        protected long nodeIdentifier

    • Constructor Detail

      • DefaultNodeIdentifierStrategy

        public DefaultNodeIdentifierStrategy()
        This constructor works in two steps: 1. Check if there's a preferred node identifier set in a system property or environment variable; 2. If no preferred node identifier exists, use a random node identifier. ### RFC-4122 - 4.1.6. Node 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 This section describes how to generate a version 1 UUID if an IEEE 802 address is not available, or its use is not desired. 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.