Question

I am having problems mapping a legacy database schema using JPA annotations.

The schema uses a table to generate unique IDs for most of the tables in the db – it has a structure of:

table_name
column_name
next_id
block_size

To get new unique ID for a record insert, you run a select like:

SELECT next_id FROM tbl_next_id WHERE table_name = 'tbl_pets' and column_name = 'pet_id'

urrgh. I know I could do this in pure hibernate by using a ‘select’ id generator (unless I just dreamt that up) – can anyone recommend the best way of handling this with JPA annotations?

Thanks

Answer 1

There is nothing better than this:

@TableGenerator(name="petsgen",
      table="tbl_next_id",
      pkColumnName="table_name",
      pkColumnValue="tbl_pets",
      valueColumnName="next_id",
      allocationSize=1
)

@Id
@GeneratedValue(strategy=GenerationType.TABLE, generator="petsgen")

Will of course not support combination of table name + column name, but should work as long as there is only one generator for table.