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public class Item {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long id;@Column(nullable = false)private String title;@Column(nullable = false)private String description;@Column(nullable = false)private Double askingPrice; @ManyToOne(fetch = FetchType.LAZY)@JoinColumn(name = "owner_id")private User owner;@OneToOne(mappedBy = "item", cascade = CascadeType.ALL, fetch = FetchType.LAZY)private Exchange exchange;">