For entities that have potential security risks for sequentially generated ID values, UUID is a commonly used class type in Spring Boot context.

Universally Unique ID

• immutable
• universally unique
• 128-bit value
• provided as class in Java

New UUID()

UUID uuid = new UUID(mostSignificant64Bits, leastSignificant64Bits);

UUID Versions

UUID V.1

• based on current timestamp & MAC address of device generating UUID
• current timestamp: measured in units of 100 nanoseconds from October 15, 1582
• MAC address of device can be replaced by random 48-bit number

UUID V.3 & V.5

• based on hashed names drawn from a unique namespace
• concept of names is not limited to textual form
  • (Ex) DNS, Object Identifiers (OID), URLs, etc.

UUID V.3 vs. V.5

UUID V.3 and V.5 differ in hashing algorithm each uses.

• UUID V.3 uses MD5 (128 bits)
• UUID V.5 uses SHA-1 (160 bits) truncated to 128 bits

UUID V.4

• generated with randomUUID() method provided by UUID class

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References

• https://docs.oracle.com/javase/8/docs/api/java/util/UUID.html
• https://www.baeldung.com/java-uuid