Spring Rest JPA在創建json時需要忽略延遲初始化

Question

我正在用彈簧托，我對一件事很感興趣。 當我分離對象並將其返回時，出現下一個錯誤： Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: failed to lazily initialize a collection of role: kz.training.springrest.entity.Publisher.books

我明白為什么。 但是我想知道是否有可以忽略此異常並設置例如default（null）值的東西。

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode
@ToString
@Entity
public class Publisher {

    @Id
    @SequenceGenerator(name = "publisher_id_seq_gen", sequenceName = "publisher_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "publisher_id_seq_gen")
    private Long id;

    private String name;

    @OneToMany
    @JoinColumn(name = "publisher_id")
    private List<Book> books;

    public Publisher(Long id, String name){
        this.id = id;
        this.name = name;
    }
}


@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Entity
public class Book {
    @Id
    @SequenceGenerator(name = "book_id_seq_gen", sequenceName = "book_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "book_id_seq_gen")
    private Long id;

    private String name;

}


@Service
public class BookService {

    @PersistenceContext
    private EntityManager entityManager;

    @Transactional
    public Publisher selectPublisher(){
        Publisher publisher = entityManager.find(Publisher.class, new Long(1));
        entityManager.detach(publisher);
        return publisher;
    }
}

Answer 1

嘗試將以下內容添加到Book和Publisher類中，以告訴json序列化程序忽略休眠字段：

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})

參考： http : //www.greggbolinger.com/ignoring-hibernate-garbage-via-jsonignoreproperties/

Answer 2

如果您知道要忽略的字段，則可以使用例如： @JsonIgnoreProperties({"books"}) 。

但是，如果您需要更通用的解決方案，則需要提供自己的轉換器，並忽略Lucas提供的鏈接中的“ hibernateLazyInitializer”和“ handler”。