Many to many Infinite recursion using Jackson and Hibernate

Question

Getting the following error because of a circular reference from the many to many relationship.

org.codehaus.jackson.map.JsonMappingException: Infinite recursion (StackOverflowError)

I've tried using @JsonIdentityInfo, @com.fasterxml.jackson.annotation.JsonIgnore, and @JsonManagedReference, but none of these are working for me. I'm using lombok, hence the @getter/setter.

User Table

@Entity
@Table(name = "user")
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="user_id", scope=User.class)
public class User implements Serializable{

    @Getter
    @Setter
    @Id
    @GeneratedValue(strategy = IDENTITY, generator = "increment")
    @GenericGenerator(name = "increment", strategy = "increment")
    public int user_id;

    @JsonManagedReference
    @Getter
    @Setter
    @com.fasterxml.jackson.annotation.JsonIgnore
    @ElementCollection(targetClass=UserInterest.class)
    @OneToMany(fetch = FetchType.EAGER, mappedBy = "pk.user", cascade=CascadeType.ALL)
    public Set<UserInterest> userInterestSet = new HashSet<UserInterest>();
}

Interest table

@Entity
@Table(name = "interest")
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="interest_id", scope=Interest.class)
public class Interest implements Serializable{

    @Getter
    @Setter
    @Id
    @GeneratedValue(strategy = IDENTITY, generator = "increment")
    @GenericGenerator(name = "increment", strategy = "increment")
    public int interest_id;

    @Getter
    @Setter
    @Column(name = "interest_name", nullable = false, length=100)
    public String interest_name;

    @Getter
    @Setter
    @com.fasterxml.jackson.annotation.JsonIgnore
    @OneToMany(fetch = FetchType.EAGER, mappedBy = "pk.interest", cascade=CascadeType.ALL)
    public Set<UserInterest> userInterestSet = new HashSet<UserInterest>();
}

UserInterest join table

@Entity
@Table(name="user_interest")
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="pk", scope=UserInterest.class)
@AssociationOverrides({
        @AssociationOverride(name="pk.user", joinColumns=@JoinColumn(name="user_id")),
        @AssociationOverride(name="pk.interest", joinColumns=@JoinColumn(name="interest_id"))
})
public class UserInterest implements Serializable {
    @Getter
    @Setter
    @com.fasterxml.jackson.annotation.JsonIgnore
    @GeneratedValue(generator = "increment")
    @GenericGenerator(name = "increment", strategy = "increment")
    public int user_interest_id;

    @EmbeddedId
    @Getter
    @Setter
    @com.fasterxml.jackson.annotation.JsonIgnore
    public UserInterestId pk;

    @Transient
    @Getter
    @Setter
    @com.fasterxml.jackson.annotation.JsonIgnore
    public User user;

    @Transient
    @Getter
    @Setter
    @com.fasterxml.jackson.annotation.JsonIgnore
    public Interest interest;
}

UserInterestId class

@Embeddable
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="id", scope=UserInterestId.class)
public class UserInterestId implements Serializable{
    @Getter
    @Setter
    @org.codehaus.jackson.annotate.JsonIgnore

    @ManyToOne(fetch = FetchType.LAZY)
    @com.fasterxml.jackson.annotation.JsonIgnore
    @JsonBackReference
    public User user;

    @Getter
    @Setter
    @JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="interest_id")
    @ManyToOne(fetch = FetchType.LAZY)
    @com.fasterxml.jackson.annotation.JsonIgnore
    @JsonBackReference
    public Interest interest;
}

When I run the following on my joined User objects I get the error:

ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
ow.writeValueAsString(userSet);

I'm pretty new to Hibernate, so would appreciate any pointers. I've read 5-10 SO articles that suggested the solutions I mentioned above, but I still haven't been able to stop the circular reference. Thanks a ton!

score 0 · Answer 1 · edited May 23 '17 at 12:22

0

You should unproxy your objects. An example from here

@SuppressWarnings("unchecked")
protected T unproxy(T entity){
    if (entity == null) {
        return null;
    }

    if (entity instanceof HibernateProxy) {
        try {
            Hibernate.initialize(entity);
        } catch (ObjectNotFoundException e) {
            return null;
        }
        entity = (T) ((HibernateProxy) entity).getHibernateLazyInitializer().getImplementation();
    }
    return entity;
}

Or this way (from here)

public <P> List<P> unproxy(Collection<P> objects) {
    Session session = sessionFactory.getCurrentSession();
    List<P> result = new ArrayList<P>();
    for (P t : objects) {
        Object unproxied = ((SessionImplementor)session).getPersistenceContext().unproxy(t);
        result.add((P) unproxied);
    }
    return result;
}

edited May 23 '17 at 12:22

Community

1
1

answered Dec 16 '15 at 06:19

StanislavL

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Hmm. Thanks. The first method doesn't work because it isn't an instanceof HibernateProxy. The second one executes okay, but doesn't change the objects. It still leads to the infinite loop. – Mark Dec 16 '15 at 06:57
What do you pass to the method(s)? – StanislavL Dec 16 '15 at 07:02
For the second one, basically this: **session = sessionFactory.openSession().beginTransaction()** .... **session.createQuery(hql) **.... **users = unproxy(users, session);** // I added session as an argument that took the place of sessionFactory.getCurrentSession(). – Mark Dec 17 '15 at 01:33
it never seems to be an instance of HibernateProxy. I also switched it to FetchType.LAZY but still no instance of HibernateProxy. – Mark Dec 17 '15 at 01:58
List of users is not proxy object. You need to unproxy every user instance in the list – StanislavL Dec 17 '15 at 05:41
I mean for the second method you mentioned. It's signature is unproxy(Collection
objects, Session session). For the first one, I used a for loop and tried: for (User user : users) {if (user instanceof HibernateProxy) { // never is an instance of hibernateproxy. @StanislavL
– Mark Dec 17 '15 at 05:44

score 0 · Accepted Answer · answered Dec 17 '15 at 07:40

Found a solution. For my ObjectWriter/ObjectMapper, I switched to com.fasterxml.jackson.databind.ObjectWriter / Mapper instead of codehaus. It seems that jsonIgnore and JsonIdentityInfo just weren't being acknowledged by codehaus.jackson.map, or at least not with my version.

Many to many Infinite recursion using Jackson and Hibernate

2 Answers2