Infinite recursion with many to many relationship

Question

I am having this error with Java hibernate many to many relationship:

Infinite recursion (StackOverflowError) (through reference chain:

org.hibernate.collection.internal.PersistentBag[0]-

com.company.nms.models.Group["users"]-

org.hibernate.collection.internal.PersistentBag[0]-

com.company.nms.models.User["groups"]

I have checked the relationship but still having this error.

In my User.java, I have:

@ManyToMany(mappedBy = "users", fetch = FetchType.EAGER)
     List<Group> groups = new ArrayList<Group>();

in Group.java, I have:

@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
     @JoinTable(name = UserConstants.REFERENCE_GROUP_USER,
     joinColumns = {@JoinColumn(name = "user_group_id")},
     inverseJoinColumns = {@JoinColumn(name = "user_id")}
     )
     List<User> users = new ArrayList<User>();

The expected result should be many to many relationship between User and Group.

Please help. Thanks

Answer 1

Produced json has infinite depth because of bidirectional reference. You can limit json's output by using @JsonManagedReference and @JsonBackReference annotations:

@ManyToMany(mappedBy = "users", fetch = FetchType.EAGER)
@JsonBackReference
List<Group> groups = new ArrayList<Group>();

@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
@JoinTable(name = UserConstants.REFERENCE_GROUP_USER,
 joinColumns = {@JoinColumn(name = "user_group_id")},
 inverseJoinColumns = {@JoinColumn(name = "user_id")}
)
@JsonManagedReference
List<User> users = new ArrayList<User>();

Or annotate one of them with @JsonIgnore.