What is the hibernate generation strategy for?

Hibernate is a Java persistence framework that offers various generation strategies to handle the primary key generation of entity objects.

The generation strategies of Hibernate include:

1. Auto-increment strategy (GenerationType.IDENTITY): Using the database’s auto-increment field to generate primary keys. Suitable for databases that support auto-increment fields, such as MySQL, SQL Server, etc.
2. Sequence strategy (GenerationType.SEQUENCE): utilizing a database sequence to generate primary keys. It is suitable for databases that support sequences, such as Oracle or PostgreSQL.
3. The table strategy (GenerationType.TABLE): generates primary keys using a separate database table. When this strategy is used, Hibernate will create a specific table for generating primary keys, and each time a primary key is generated, a unique value will be retrieved from that table.
4. UUID strategy (GenerationType.UUID): Utilizes Universally Unique Identifier (UUID) to generate primary keys. Hibernate automatically creates a unique UUID as the primary key.
5. Custom strategy (GenerationType.AUTO): Use a custom generation strategy to create primary keys. Developers can customize the primary key generation strategy by implementing the IdentifierGenerator interface.

Developers can use annotations on the primary key fields of entities to specify generation strategies, such as:

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

In the examples above, an auto-increment strategy is used to generate primary keys.