Question

i have a oneToMany and ManyToOne mapping in my models:

class User

@OneToMany (cascade = { CascadeType.REFRESH, CascadeType.DETACH }, fetch = FetchType.EAGER)
    private Set<Judgement> judgements;

class Judgement

@ManyToOne(cascade = { CascadeType.REFRESH, CascadeType.DETACH})
    @JoinColumn(name = "user_id")
    private User judge;

and in DB, i have to tables as Users and Judgements, when i tried to run my code, it showed error as:

Caused by: org.postgresql.util.PSQLException: ERROR: relation "users_judgements" does not exist

does that mean i have to create the table users_judgements by hand, jpa cannot automatically create the relationship for me? RoR can do it…Thanks.

Answer 1

If you have a foreign key from USER table, user_id, in JUDGMENT table then there is no need to have another table. That will be the @JoinColumn(name = “user_id”).

See if you are missing something; I can not see any “mappedBy” attribute, which will be “user” in your case.

Please take a look at this article; page 4 that the link will take you, give details about one-to-many relationship. It will be worth reading the whole article.

http://www.javaworld.com/javaworld/jw-01-2008/jw-01-jpa2.html?page=4

Also, the part 1 of the same tutorial is good for basics;

http://www.javaworld.com/javaworld/jw-01-2008/jw-01-jpa1.html