JPA primary key auto generate

Question

my primary key entity look like below

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

when i run, i get error

cou

Answer 1

The @GeneratedValue(strategy=GenerationType.TABLE) tells the JPA provider to use a table to get IDs from when inserting newly created entities into the database.

When using Hibernate as provider, this will result in a table hibernate_sequences which has two columns: the entity name, and the max identity already assigned to this entity. Here, it seems Hibernate doesn't succeed to get the next ID from it for your entity but it's hard to say exactly why because you didn't provide enough informations for that.

So, could you please provide the full stacktrace? Also, please turn logging with hibernate.show_sql property set to true and set the proper log level log4j.logger.org.hibernate.SQL=DEBUG. Join the log to your question if possible.

Maybe just check that you did configure the correct hibernate.dialect for Oracle. Actually, join your hibernate configuration too if possible.

PS: The "traditional" way to generate PK with Oracle is to use sequences (you could let Hibernate guess the best strategy for your database type using GenerationType.AUTO or force it using SEQUENCE) but I'll assume you want the resultant data structure be database agnostic. If not, I'd suggest to go for sequences instead.

EDIT: Answering a comment from the OP about GenerationType.AUTO. Indeed, the default is a single global sequence called hibernate_sequence and this might be a problem. But, with the setup shown below, you can use GenerationType.AUTO and still control the name of the sequence for the cases where the database uses sequences:

@Id
@GeneratedValue(strategy=GenerationType.AUTO, generator="my_entity_seq_gen")
@SequenceGenerator(name="my_entity_seq_gen", sequenceName="MY_ENTITY_SEQ")
private long id;

In other words, you can use use a different sequence name for each table without losing portability.