通过ID而非实体添加与实体的关系

Question

I'm creating a web application in Spring where I've some transactions and categories. The transactions have a ManyToOne relation to Category . Now I want to set the category by id and not by Category (as object).

The reason why I couldn't use the EntityManager is because I needed this in a EntityListener . In my answer I found a way to autowire this EntityListener which fixed my problem.

Is this possible in Spring ?

I found this on StackOverflow Hibernate - Add member entity instance by ID , but I can't use the EntityManager where I need it.

This is my transaction entity:

@Entity
@ToString
@Slf4j
@EntityListeners(TransactionListener.class)
@Getter
@Setter
public class Transaction {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    @Column
    private long account;
    @Column
    @JsonFormat(pattern = "dd-MM-yyyy")
    private LocalDate date;
    @Column
    private float amount;
    @Column(columnDefinition = "text")
    private String description;
    @Column(unique = true)
    private String hash;
    @ManyToOne
    @JoinColumn(name = "category_id")
    @JsonIgnoreProperties("transactions")
    private Category category;
}

and this is my category entity

@Entity
@ToString
@Getter
@Setter
@EntityListeners(CategoryListener.class)
public class Category {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column
    private String name;
    @Column
    private String color;
    @Column
    private String[] matchers;
    @JsonProperty(access = JsonProperty.Access.READ_ONLY)
    @OneToMany(mappedBy = "category")
    @JsonIgnoreProperties("category")
    private List<Transaction> transactions;
}

Answer 1

I could not autowire the EntityManager because I needed this in a entity listener and these are not autowired. I found a way to get this autowired on Injecting a Spring dependency into a JPA EntityListener .

Thanks for everyone who helped me! :)