JPA Bidirectional Onetomany json endless loop

Question

the program under this particular environment： EJB3.0 + JPA + jersey Web Service

First Entity :

@Entity
@Table(name = "student_by_test_yao")

public class StudentTest implements Serializable {
    @Id
    @GeneratedValue
    private Integer id;
    private String name;

    @ManyToOne
    @JoinColumn(name = "class_id")
    private ClassTest classes;

    public StudentTest() {}
}

Second Entity:

@Entity
@Table(name = "class_by_test_yao")
public class ClassTest implements Serializable{
    @Id
    @GeneratedValue
    private Integer id;
    private String name;

    @OneToMany(mappedBy = "classes",cascade = CascadeType.ALL, fetch=FetchType.EAGER)
    private List<StudentTest> students;

    public ClassTest() {}
}

When I get the ClassTest 's students list. Exception is:

com.fasterxml.jackson.databind.JsonMappingException:
Infinite recursion (StackOverflowError)

If I change the fetch FetchType.LAZY the Exception is:

org.hibernate.LazyInitializationException: 
failed to lazily initialize a collection of role: 
cn.gomro.mid.core.biz.goods.test.ClassTest.students, 
could not initialize proxy - no Session

How to resolve my problems?

https://stackoverflow.com/questions/17542240/how-to-serialize-only-the-id-of-a-child-with-jackson This may help. The best way avoid loop. — sp518, Nov 19 '18 at 06:52
For anyone having this issue, best solution is: https://stackoverflow.com/a/18288939/6835976 — Olezt, Mar 19 '19 at 13:49

score 5 · Answer 1 · answered Apr 05 '19 at 22:45

@JsonIgnore
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "userId")
private User user;

it really worked. I just tried that on Bi-Directional @ManyToOne mapping. It fixed

com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError)

score 3 · Answer 2 · answered Sep 01 '16 at 07:58

3

Try to add @JsonIgnore annotation to one of fields to avoid looping

answered Sep 01 '16 at 07:58

Vyacheslav Tsivina

297
3
12

@JsonIgnore is useless. still in Excepton at 'org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:167) Caused by: com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError)' – Adam Yao Sep 01 '16 at 08:09
Hm, strange. It helped me when I had the same Exception – Vyacheslav Tsivina Sep 01 '16 at 08:13

score 1 · Answer 3 · answered Sep 01 '16 at 08:49

1

For bidirectional relationships you can use these annotations:

@JsonManagedReference for the parent and @JsonBackReference for the child.

Also, this link might help: Jackson – Bidirectional Relationships

answered Sep 01 '16 at 08:49

Alexander H

198
1
8

Actually I need to get List in ClassTest also get Entity in StudentTest. – Adam Yao Sep 19 '16 at 09:13
I'm sorry, I'm not sure I got that.. You want to be able to fetch a StudentTest from a ClassTest and a ClassTest from a StudentTest? – Alexander H Sep 20 '16 at 11:03
1

Using \@JsonManagedReference and \@JsonBackReference you should be able to reconstruct both directions of the relationship during de-serialization. Of course in the JSON representation both sides of the relationship are not serialized, otherwise you would incur in the stack overflow since the entites would keep referencing each other. – Alexander H Sep 20 '16 at 11:52
@AlexanderH So I'm pretty sure what OP was trying to do is impossible _but_ what if I only wanted the `List>.length`? Perhaps it's possible to see how many relationships exist from the opposite side without causing an infinite recursion? – medley56 Feb 16 '18 at 21:33
I would define a `@JsonProperty` on the `ClassTest` side. Something like: `@JsonProperty public int classSize() { return classes.getStudents().size(); }` – Alexander H Feb 19 '18 at 12:54

score 1 · Answer 4 · edited Mar 17 '18 at 23:53

1

Snippet must help you.

@JsonIgnore
@ManyToOne
@JoinColumn(name = "columnName", referencedColumnName = "id")
private Class class;

edited Mar 17 '18 at 23:53

Syed Zain Ali

1,206
1
14
20

answered Mar 16 '18 at 18:58

Danilo Santos

11
3

JPA Bidirectional Onetomany json endless loop

4 Answers4