如何使用“多对多”关系标准？

Question

Good afternoon. Learn Hibernate, it became necessary to write the following query using the criteria. There are two entities - a fruit shop and the type of communication - many to many. Accordingly, we have literally three tables (and the corresponding classes of Java): Fruit (id, name), Shop (id, name) and ShopFruit (shop_id, fruit_id). So, as with the criterion to obtain a list of stores selling, say, a tangerine? Thanks in advance.

Answer 1

I think you can use an alias like so:

List questions = session.createCriteria(Shop.class)
  .createAlias("Fruits", "f")
  .add(Restrictions.eq("f.name", "tangerine"))
  .list();

See also this question . However, I think you can also solve this with a set in your Hibernate mapping for Fruit:

<set name="stores" table="ShopFruit" cascade="all">
  <key column="fruit_id" />
  <many-to-many column="store_id" />
</set>

Extends your Fruit class with a stores set:

class Fruit {
  ...
  Set<Store> stores;
  ...
}

If you than load the "tangerine" Fruit object from the database, the stores variable should have all the stores selling it.