Creating Circular referencing in Hibernate
There are situations when we need to create tree json. For that we need to create self join on the same Entity to make Parent child relationship on same entity.
Following is the example:
@Entity
@Table(name = "tree")
public class Tree implements Serializable {
private static final long serialVersionUID = 663408095532480033L;
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="id")
private String id;
@Column(name="fruit")
private String fruit ;
@ManyToOne
@JoinColumn(name="child_id", nullable=false)
private Tree rootId;
}
When you will try to retrieve the following entity you will get Child First and inside it will get parents.
In order to retrieve parent first and then inside get childs following should be the structure.
@Entity
@Table(name = "tree")
public class Tree implements Serializable {
private static final long serialVersionUID = 663408095532480033L;
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="id")
private String id;
@Column(name="fruit")
private String fruit ;
@ManyToOne
@JoinColumn(name="child_id", nullable=false)
private Tree rootId;
@OneToMany(mappedBy=rootId)
private List<Tree> children;
}
Here when you will return the entity to frontend user issue of infinite json refrencing will come in order to resolve the issue need to add json annotations in entity that is following :
@Entity
@Table(name = "tree")
public class Tree implements Serializable {
private static final long serialVersionUID = 663408095532480033L;
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="id")
private String id;
@Column(name="fruit")
private String fruit ;
@ManyToOne
@JoinColumn(name="child_id", nullable=false)
@JsonBackReference
private Tree rootId;
@OneToMany(mappedBy=rootId)
@JsonManagedReference
private List<Tree> children;
}
Enitity would return the following Json:
[
{
"id": "1",
"fruit": "ROOT",
"child": [
{
"id": "2",
"fruit": "CHILD",
"child": [
{
"id": "3",
"fruit": "CHILD1",
"child": []
}
]
}
]
},
{
"id": "4",
"fruit": "Root",
"child": [
{
"id": "5,
"fruit": " Root Child 1",
"child": [
{
"id": "6",
"fruit": " Root Child 2"
"child": []
}
]
}
]
Hope this will help happycoding. :)
