Java 在 Spring Data JPA 中处理实体继承的最佳方式
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Best way of handling entities inheritance in Spring Data JPA
提问by Andrea
I've three JPA entityclasses A, Band Cwith the following hierarchy:
我有三个JPA 实体类A，B并且C具有以下层次结构：
A
|
+---+---+
| |
C B
That is:
那是：
@Entity
@Inheritance
public abstract class A { /* ... */ }
@Entity
public class B extends A { /* ... */ }
@Entity
public class C extends A { /* ... */ }
Using Spring Data JPA, what is the best way to write repositoriesclasses for such entities?
使用Spring Data JPA，为此类实体编写存储库类的最佳方法是什么？
I know that I can write these:
我知道我可以写这些：
public interface ARespository extends CrudRepository<A, Long> { }
public interface BRespository extends CrudRepository<B, Long> { }
public interface CRespository extends CrudRepository<C, Long> { }
but if in the class Athere is a field nameand I add this method in the ARepository:
但是如果在类中A有一个字段name并且我在ARepository：
public A findByName(String name);
I've to write such method also in the other two repositories, and this is a bit annoying.. Is there a better way to handle such situation?
我也必须在其他两个存储库中编写这样的方法，这有点烦人..有没有更好的方法来处理这种情况？
Another point I would like to have is that ARespositoryshould be a read-only repository (i.e. extend the Repositoryclass) while the other two repositories should expose all the CRUD operations.
我想要的另一点是它ARespository应该是一个只读存储库（即扩展Repository类），而其他两个存储库应该公开所有 CRUD 操作。
Let me know possible solutions.
让我知道可能的解决方案。
采纳答案by Andrea
I used the solution also described in this postfrom Netgloo's blog.
我使用了Netgloo 博客中这篇文章中描述的解决方案。
The idea is to create a genericrepository class like the following:
这个想法是创建一个通用的存储库类，如下所示：
@NoRepositoryBean
public interface ABaseRepository<T extends A>
extends CrudRepository<T, Long> {
// All methods in this repository will be available in the ARepository,
// in the BRepository and in the CRepository.
// ...
}
then I can write the three repositories in this way:
那么我可以这样写三个存储库：
@Transactional
public interface ARepository extends ABaseRepository<A> { /* ... */ }
@Transactional
public interface BRepository extends ABaseRepository<B> { /* ... */ }
@Transactional
public interface CRepository extends ABaseRepository<C> { /* ... */ }
Moreover, to obtain a read-only repository for ARepositoryI can define the ABaseRepositoryas read-only:
此外，要获取只读存储库，ARepository我可以将其定义ABaseRepository为只读：
@NoRepositoryBean
public interface ABaseRepository<T>
extends Repository<T, Long> {
T findOne(Long id);
Iterable<T> findAll();
Iterable<T> findAll(Sort sort);
Page<T> findAll(Pageable pageable);
}
and from BRepositoryextend also the Spring Data JPA's CrudRepositoryto achieve a read/write repository:
并BRepository扩展 Spring Data JPACrudRepository以实现读/写存储库：
@Transactional
public interface BRepository
extends ABaseRepository<B>, CrudRepository<B, Long>
{ /* ... */ }
