如何使用 Lombok 在 Spring/JPA/Hibernate 中获取带有所有子实体和子实体的父实体

Question

I have these entities where Shop entity is parent:

@Data
@NoArgsConstructor
@Entity
@DynamicUpdate
@Table(name = "Shop", schema = "public")
public class ShopDao {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;
    private String name;
    private String processedStatus;
    @OneToMany(mappedBy = "shopDao", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<BookDao> bookDaoList;
}

@Data
@NoArgsConstructor
@Entity
@ToString(exclude = {"shopDao"})
@Table(name = "Book", schema = "public")
public class BookDao {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;
    private String name;
    private String author;
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "other_id", referencedColumnName = "id")
    private OtherDao otherDao;

    @ManyToOne
    @JoinColumn(name = "shop_id", nullable = false)
    private ShopDao shopDao;
}

@Data
@NoArgsConstructor
@Entity
@ToString(exclude = {"bookDao"})
@Table(name = "Other", schema = "public")
public class OtherDao {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;
    private String metadata;

    @OneToOne(mappedBy = "otherDao", fetch = FetchType.EAGER)
    private BookDao bookDao;
}

And these are repos:

@Repository
public interface ShopRepo extends JpaRepository<ShopDao, Long> {
    @EntityGraph(attributePaths = {"bookDaoList"})
    List<ShopDao> findAllByProcessedStatus(String processedStatus);
}

@Repository
public interface BookRepo extends JpaRepository<BookDao, Long> {
}

@Repository
public interface OtherRepo extends JpaRepository<OtherDao, Long> {
}

When i'm using findAllByProcessedStatus() function, i get BookList inside Shop object correctly, but each Book can't reach their Other objects and i get LazyInitializationException: screenshot

How do i fix that problem?

Answer 1

Actually, with spring data's @EntityGraph all you need is :

@Repository
public interface ShopRepo extends JpaRepository<ShopDao, Long> {
    @EntityGraph(attributePaths = {"bookDaoList.otherDao"})
    List<ShopDao> findAllByProcessedStatus(String processedStatus);
}

This is the most convenient way. For more complex relations, you could define a @NamedEntityGraph, and provide subgraphs, like so .

What I find intriguing, is that the BookDao is the owner of this relation, so I would expect it to be eagerly loaded, since you haven't specified a the Lazy fetch mode explicitly ...