Saving in one shot two parents and one child Spring JPA - spring

Question

I have never had a case where I want to save multiple parents and one child in one shot. In my case, I have two parent entities and one child. The two parent entities have a foreign key on the child entity.
I have an example like this ->
#Entity
#Table("parentA")
public class ParentA
{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long ID;
#OneToMany(cascade = CascadeType.ALL, mappedBy="parentA")
private List<Child> child;
// Getters and Setters and some methods
}
#Entity
#Table("ParentB")
public class ParentB
{
#Column("CODE")
private Long code;
#OneToMany(cascade = CascadeType.ALL, mappedBy="parentB")
private List<Child> child;
// Getters and Setters and some methods}
#Entity
#Table("Child")
public class Child
{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column("ID")
private Long ID;
#Column("parentA_ID")
private Long parentAId;
#Column("code")
private String code;//from parentB
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "ID", referencedColumnName = "parentA_ID")
private ParentA parentA;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "code", referencedColumnName = "code")
private ParentB parentB;
// Getters and Setters and some methods}

Answer 1

You just add attribute cascade = CascadeType.PERSIST to Child fields:
#Entity
public class Child {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
#JoinColumn
private ParentA parentA;
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
#JoinColumn
private ParentB parentB;
// ...
}
public interface ChildRepository extends JpaRepository<Child, Integer> {
}
Then the parent entities will be saved when you save the child entity:
ChildRepository childRepo;
// ...
var child = new Child();
var parentA = new ParentA();
var parentB = new ParentB();
parentA.setChild(List.of(child));
parentB.setChild(List.of(child));
child.setParentA(parentA);
child.setParentB(parentB);
childRepo.save(child);
You can see that a single save inserted all three rows:
DEBUG n.t.d.l.l.SLF4JQueryLoggingListener -
Name:dataSource, Connection:4, Time:52, Success:True
Type:Prepared, Batch:False, QuerySize:1, BatchSize:0
Query:["insert into parenta values ( )"]
Params:[()]
DEBUG n.t.d.l.l.SLF4JQueryLoggingListener -
Name:dataSource, Connection:4, Time:0, Success:True
Type:Prepared, Batch:False, QuerySize:1, BatchSize:0
Query:["insert into parentb values ( )"]
Params:[()]
DEBUG n.t.d.l.l.SLF4JQueryLoggingListener -
Name:dataSource, Connection:4, Time:0, Success:True
Type:Prepared, Batch:False, QuerySize:1, BatchSize:0
Query:["insert into child (parenta_id, parentb_id) values (?, ?)"]
Params:[(3,3)]