Pfthb

I'm trying to setup a Spring MVC Rest API using Angular in front end.
I'm strictly beginner for both technologies and it's a real challenge.

I'm going right to the point : I have an entity which refers to itself. For example, a category can have or not a parent category... For this I generated an Entity from an existing table...

I tried using fetch = fetchtype.eager to get the datas and it didn't provide the expected result.

Here is my Entity :

package com.company.app.model;

import java.io.Serializable;
import javax.persistence.*;

import com.fasterxml.jackson.annotation.JsonBackReference;
import com.fasterxml.jackson.annotation.JsonManagedReference;

import java.util.Date;
import java.util.List;

@Entity
@Table(name="categories")
@NamedQuery(name="Category.findAll", query="SELECT c FROM Category c")
public class Category implements Serializable 
 private static final long serialVersionUID = 1L;

 @Id
 @GeneratedValue
 private Long id;

 ....

 //bi-directional many-to-one association to Category
 @ManyToOne
 @JsonManagedReference
 private Category category;

 //bi-directional many-to-one association to Category
 @OneToMany(mappedBy="category", fetch = FetchType.EAGER) 
 @JsonBackReference
 private List<Category> categories;

 //bi-directional many-to-one association to CategoryProduct
 @OneToMany(mappedBy="category")
 @JsonBackReference
 private List<CategoryProduct> categoryProducts;


 public Category() 
 

 // Getters, setters and other methods generated with JPA

My issue is that i would like to generate an Json which the "top level" categories which do not have parents and all their children categories. Technically it would look like this

 [ 
 
 // Top level category 
 "id":1,
 "name":"....",
 "desc": "....."
 "children" : [
 
 "id":12,
 "name":"....",
 "desc": "....."
 , 
 
 "id":14,
 "name":"....",
 "desc": "....."
 
 ...
 ]
 "admin": 
 "id":1,
 "createdAt":1541869810000,
 "deletedAt":null,
 "email":"david.vera@9online.fr",
 "login":"admin",
 "name":"Vera",
 "password":"admin",
 "surname":"David",
 "updatedAt":1542150000000
 ,
 
 ]

In my Controller I have a method for listing the categories and it works as expected.

@GetMapping(path="/categories", produces= "application/json")
public List<Category> getAllCategories(Model model) 
 return categoryRepository.findAll();

Thanks for your help