如何使用 Lombok 在 Spring/JPA/Hibernate 中獲取帶有所有子實體和子實體的父實體

Question

我有這些實體，其中 Shop 實體是父實體：

@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;
}

這些是回購：

@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> {
}

當我使用findAllByProcessedStatus()函數時，我在 Shop 對象中正確獲取了 BookList，但每本書都無法訪問它們的其他對象，並且我得到 LazyInitializationException: screenshot

我該如何解決這個問題？

Answer 1

實際上，使用 spring 數據的 @EntityGraph 您只需要：

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

這是最方便的方式。 對於更復雜的關系，您可以定義一個@NamedEntityGraph，並提供子圖，就像這樣。

我覺得有趣的是 BookDao 是這種關系的所有者，所以我希望它能夠被急切地加載，因為您沒有明確指定 Lazy fetch 模式......