Why am I getting Mapping Exception?

Question

I am getting :

org.hibernate.MappingException: Foreign key (FKBB979BF4266AA123:address [a_id]))
must have same number of columns as the referenced 
primary key (         


        

Answer 1

You need to specify different table name for many-to-many association as it's handled by a separate table:

Note that now references to person_addresses table. With default configuration, Hibernate is able to create it automatically.

There's another mistake that I see: ID generator for Address entity should not be foreign, it's usually used in 1-to-1 relationships (uses ID of another associated object). You can use the same 'increment' use used for Person entity: