休眠中的多对多自引用关联

Question

I want to do this:

Person <--Many-to-many---> Person

I want to have a relation where one person can have many (more than one) parents and one parent can have many childs (more then one)

My hibernate mapping

@Entity
class Person{

    @Id
    @Column
    long id;

    @Column
    String name;

    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(name = "Person_Parent", 
      joinColumns={ @JoinColumn(name = "parent_ID") },
      inverseJoinColumns = { @JoinColumn(name = "child_ID")})
    private Set<Person> parent = new HashSet<Person>();

    @JsonIgnore
    @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(name = "Person_Parent", 
      joinColumns={ @JoinColumn(name = "child_ID") },
      inverseJoinColumns = { @JoinColumn(name = "parent_ID")})
    private Set<Person> child = new HashSet<Person>();
}

Is this mapping correct? how to make this relation bidirectional. so that if I add a Parent. that Parent's child collection should be updated.

Answer 1

Without knowing for certain what your issue is, I believe you might be having problems because you have not set a "mappedBy" value for "owning" side of the relationship. Example:

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private Set<Person> parent = new HashSet<Person>();

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy="parent")
private Set<Person> child = new HashSet<Person>();

(I've removed the @JoinTable for brevity's sake.) Furthermore, you may be interested in a better way of suppressing your JSON serialization by using the following annotations as opposed to @JsonIgnore :

@JsonBackReference
private Set<Person> parent = new HashSet<Person>();

@JsonManagedReference
private Set<Person> child = new HashSet<Person>();