Can I get the list of objects in relation #OneToMany? - spring

Question

I've got 2 classes: Device and Category. 1 Device can have 1 assigned category, but 1 category can have assigned many different devices.
#Entity
#Data
#Table(name = "devices")
public class Device implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String description;
#Column(name="amount_of_items")
private Integer amountOfItems;
private BigDecimal price;
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "category_id")
private Category category;
public Device(String name, String description, Integer amountOfItems, BigDecimal price, Category category){
this.name = name;
this.description = description;
this.amountOfItems = amountOfItems;
this.price = price;
this.category = category;
}
public Device() {}
}
#Entity
#Data
#Table(name = "categories")
public class Category implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String description;
#OneToMany(mappedBy = "category", fetch = FetchType.EAGER)
private List<Device> devices = new ArrayList<>();
public Category(String name, String description){
this.name = name;
this.description = description;
}
public Category() { }
}
Can I get the actual list of devices for one Category? The below code returns me a null list of devices:
Category category = new Category("Urzadzenia AGD", "tylko dla klientow premium");
categoryRepository.save(category);
Device device = new Device("pralka", "samoobslugowa", 50, new BigDecimal("220"),
category);
deviceRepository.save(device);
System.out.println(category.getDevies()) ---> returns NULL
Can I do it by calling a getter like above?

Answer 1

save method already return value after save in Database you can use this
Category category = new Category("Urzadzenia AGD", "tylko dla klientow premium");
category= categoryRepository.save(category);
Device device = new Device("pralka", "samoobslugowa", 50, new BigDecimal("220"),
category);
deviceRepository.save(device);
System.out.println(category.getDevies())
and you must be make setter and getter method in your class
after this you have problem stackover flow exciption becouse the all device called category and categore call Devices
you can used #JsonIgnore annotation
Like this :
#OneToMany(mappedBy = "category", fetch = FetchType.EAGER)
#JsonIgnore
private List<Device> devices = new ArrayList<>();