Spring hibernate ignore json object - spring

Question

I need to remove cart object from json, but only in one controller method and that is:
#GetMapping("/users")
public List<User> getUsers() {
return userRepository.findAll();
}
User
#Entity
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#NotBlank(message = "Name cannot be empty")
private String name;
#OneToOne
private Cart cart;
}
Cart
#Entity
public class Cart {
#Id
private String id = UUID.randomUUID().toString();
#OneToMany
private List<CartItem> cartItems = new ArrayList<>();
#OneToOne
#JsonIgnore
#OnDelete(action = OnDeleteAction.CASCADE)
private User user;
}
I have done it with simple solution so i loop trough all users, and set their cart to null,and then anotated user entity with #JsonInclude(JsonInclude.Include.NON_NULL)
But i dont think this is propper solution, so im searching for some better solution..
How am i able to do this?
Thanks...

Answer 1

You can create DTO (data transfer object) class like this:
#Data
public class UsersDto {
private Integer id;
private String name;
public UsersDto(User user) {
this.id = user.id;
this.name= user.name;
}
}
and than create List<UsersDto>
#GetMapping("/users")
public List<UsersDto> getUsers() {
List<User> users = userRepository.findAll();
return users
.stream()
.map(o -> new UsersDto(o))
.collect(Collectors.toList());
}

Answer 2

You should use Data Projection.
In your use case, you can use an interface projection:
public interface CartlessUser {
Integer getId();
String getName();
}
And In your repository:
public interface UserRepository extends JpaRepository<User, Integer> {
List<CartlessUser> findAllBy();
}
The interface projection will help generate the sql query for only selecting the id, name fields. This will save you from fetching the Cart data when you're just going to throw it away anyways.