From a data access perspective, JPA supports two major types of identifiers:
The assigned identifiers must be manually set on every given entity prior to being persisted. For this reason, assigned identifiers are suitable for natural keys.
For synthetic Primary Keys, we need to use a generated entity identifier, which is supported by JPA through the use of the
There are four types of generated identifier strategies which are defined by the
AUTO identifier generator strategy chooses one of the other three strategies (
TABLE) based on the underlying relational database capabilities.
IDENTITY maps to an auto-incremented column (e.g.
IDENTITY in SQL Server or
AUTO_INCREMENT in MySQL) and
SEQUENCE is used for delegating the identifier generation to a database sequence, the
TABLE generator has no direct implementation in relational databases.
This post is going to analyze why the
TABLE generator is a poor choice for every enterprise application that cares for performance and scalability.
Continue reading “Why you should never use the TABLE identifier generator with JPA and Hibernate”
As previously explained, using the JPA entity business key for
hashCode is always best choice. However, not all entities feature a unique business key, so we need to use another database column that is also unique, like the primary key.
But using the entity identifier for equality is very challenging, and this post is going to show you how you can use it without issues.
Continue reading “How to implement equals and hashCode using the JPA entity identifier (primary key)”