问题
I am trying to fetch record by doing a join. I am new to spring jparepository. I understand that there is separate repository for each entity(table) where when i implement i need to define the entity and datatype of primary key.
Could anyone please suggest how can I fetch record by joining two tables.
I have two repo as below:
public interface AEntityRepository extends JpaRepository<AEntity, Integer>
public interface BEntityRepository extends JpaRepository<BEntity, Integer>
I want to join above two entity(AEntity, BEntity). I know I can have custom query using something like below:
@Query("SELECT ****** FROM AEntity ae")
AEntity findCustomrRecords();
However can I write the same kind of query (join query) with join. Do i need to have a separate repository implementing some other class.
Can anyone please help.
I am using mysql.
回答1:
I understand that there is separate repository for each entity(table)
This is a very common misunderstanding. You do not want to have a repository per entity, but per aggregate root. See http://static.olivergierke.de/lectures/ddd-and-spring/
Regarding your specific problem at hand: Creating a custom method in your repository interface and annotating it with a JPQL should do the trick. So you get something like:
@Query("select a from BEntity b join b.a a where b.foo = :foo")
AEntity getAllFooishAs(String foo);
You can use any join syntax JPQL offers in the query.
来源：https://stackoverflow.com/questions/43273118/join-more-than-one-table-in-spring-jparepository