Spring rest JPA need to ignore lazy initialization when creating json

Question

I'm using spring rest and I'm interested in one thing. When I detach my object and return it back I'm getting the next error: 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

I understand why. But I wanna know if there is something that can ignore this exception and set default(null) value for example.

@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;
    }
}

LucasP · Accepted Answer · 2018-06-04 13:25:22Z

1

Try adding the following to your Book and Publisher classes to tell your json serializer to ignore the hibernate fields:

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

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

edited Jun 4, 2018 at 13:25

answered Jun 4, 2018 at 13:19

LucasP

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2 Comments

Arlo Guthrie Over a year ago

You can also just add @JsonIgnore annotation to the property.

LucasP Over a year ago

@ArloGuthrie those properties don't exist on the classes in the source code. They are created by hibernate at runtime when it proxies the Book and Publisher classes.

Rohit · Accepted Answer · 2018-06-04 19:36:02Z

0

If you know which fields you want to ignore then you can use for eg: @JsonIgnoreProperties({"books"}).

But if you want a more generic solution you need to provide own converter alongwith ignoring "hibernateLazyInitializer" and "handler" like in the link Lucas provided.

answered Jun 4, 2018 at 19:36

Rohit

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