One to Many bidirectional - spring

Question

I have problems with Many to One relationship because I don't show correctly the entity.
Could anyone helps to me ?
I attached my code.
Invoice
#Entity
#Table(name = "invoices")
#JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,property = "id")
public class Invoice {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
private String clave;
#OneToMany(mappedBy = "invoice", cascade = CascadeType.REMOVE, fetch = FetchType.LAZY, orphanRemoval = true)
private List<InvoiceLine> lines;
InvoiceLines
#Entity
#Table(name = "invoice_lines")
#JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,property = "id")
public class InvoiceLine {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "product", nullable = false)
private String product;
#ManyToOne
#JoinColumn(name = "invoice_id", referencedColumnName = "id", nullable = false)
private Invoice invoice;
Controller
#RestController
public class InvoiceController{
#Autowired
private InvoiceRepository invoiceRepository;
#Autowired
private InvoiceLineRepository invoiceLineRepository;
#GetMapping("/")
public Iterable<Invoice> findAllnvoices(){
return invoiceRepository.findAll();
}
#GetMapping("/invoiceLine")
public Iterable<InvoiceLine> findAllInvoiceLine(){
return invoiceLineRepository.findAll();
}
#GetMapping("/{id}")
public Optional<Invoice> findTagByInvoice(#PathVariable("id") Long id){
return invoiceRepository.findById(id);
}
}
The response when I call a endpoint invoiceLine :
[
{
"id": 1,
"product": "Tag1-ES",
"invoice": {
"id": 1,
"clave": "Tag1",
"lines": [
1,
{
"id": 2,
"product": "Tag1-FR",
"invoice": 1
},
{
"id": 3,
"product": "Tag1-IT",
"invoice": 1
}
]
}
},
2,
3
]
My question :Why is not showing correctly the response the ManyToOne entity if I have all correct ?

Answer 1

If I understood your problem correctly after the comments, you are bothered by the "numbers" that are displayed. Those numbers are used to avoid infinite recursion, and they refer to entities that were already displayed.
So the number "2" would be this actually:
{
"id": 2,
"product": "Tag1-FR",
"invoice": 1
}
If a representation like that is not used, then the whole invoice and it's items would be repeated infinitely.
There are several different ways to avoid this behavior, such as using #JsonIgnore or #JsonBackReference and #JsonManagedReference. Take a look at this explanation about their differences
Difference between #JsonIgnore and #JsonBackReference, #JsonManagedReference