JPA - Allow null parent in Recursive query - spring-data-jpa

Question

I want to create Organization Structure using JPA. If I insert data using my controller, it will throw a PSQLException because the first node's parent is null. But if I input the first node manually into DB, it works for the next node. I read about this and other postings but no luck for me.
This is my entity:
#Entity
#Table(name = "tree")
public class Node implements Serializable {
#Id
private int id;
private String name;
#OneToMany(
cascade = CascadeType.ALL
)
#JoinColumn(name = "parent_id", nullable = true)
#OrderColumn
#JsonManagedReference
private Set<Node> children = new HashSet<>();
#Basic(optional = true)
#ManyToOne(
fetch = FetchType.LAZY,
optional = true
)
#JoinColumn(name = "parent_id", nullable = true)
#JsonBackReference
private Node parent;
public void addNode(Node node){
this.getParent().getChildren().add(node);
node.setParent(this.getParent());
}
// Getter setter was removed for brevity
}
This is my controller:
#RestController
#RequestMapping("/node")
public class NodeController {
#Autowired
private NodeRepository nodeRepository;
#GetMapping
public #ResponseBody Iterable<Node> index(){
return nodeRepository.findByParentIsNull();
}
#PostMapping
public String add(
#RequestBody List<Node> nodes){
nodes.stream().forEach(
node -> {
node.addNode(node);
}
);
nodeRepository.saveAll(nodes);
return "nice";
}
}
And, this is my data sample:
[
{
"id":8,
"name":"Top Parent",
"parent":{}
},{
"id":9,
"name":"Node 1",
"parent":{
"id":8
}
},{
"id":10,
"name":"Node 2",
"parent":{
"id":8
}
},{
"id":11,
"name":"Node 3",
"parent":{
"id":9
}
}
]
The Expected Result after inserting via controller is:
id |name |parent_id
===========================
8 |Top Parent |null
9 |Node 1 |8
10 |Node 2 |8
11 |Node 3 |9
Let me know if something unclear. Thank in advance!

Answer 1

I find a workaround for my problem. So, I put here if someone faces a similar problem with me.
I added a NativeQuery in my repository like this:
#Query(value = "insert into tree values(:id,:name)", nativeQuery = true)
void saveTop(#Param("id")int id,#Param("name")String name);
And then I added some lines in my controller like this:
#PostMapping("/top")
public void addTop(#RequestBody Node node){
nodeRepository.saveTop(node.getId(),node.getName());
}
Basically, I create an endpoint("/node/top") to insert top node for my structure organization tree manually.