[FIXED] Infinite recursion with many to many relationship

Issue

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

Solution

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.

Answered By - Andronicus