Implementing Domain-Driven Design

Persistence Mechanism Generates Identity

Delegating the generation of unique identity to a persistence mechanism has some unique advantages. If we call on the database for a sequence or incrementing value, it will always be unique.

Depending on the range needed, the database can generate a unique 2-byte, 4-byte, or 8-byte value. In Java, a 2-byte short integer would allow for up to 32,767 unique identities; a 4-byte normal integer would afford 2,147,483,647 unique values; and an 8-byte long integer would provide up to 9,223,372,036,854,775,807 distinct identities. Even zero-filled text representations of these ranges are narrow, at five, ten, and 19 characters respectively. These can also be employed to create composite identities.

One possible ...