@ElementCollection 在 @OneToMany 上，反之亦然

Question

Let's assume I do have an Offer entity. It has a property salaries that may be a list of Salary objects. The Salary cannot exist without an Offer , so does it mean I should use @ElementCollection or may not? When should we use @ElementCollection and when @OneToMany . The same question comes to my mind when we talk about @Embeddable and @Embedded , is it worth using it, or perhaps it's better to have a @OneToOne relationship.

class Salary(
    val salary_from: Integer,
    val salary_to: Integer,
    val salary_type: Type
)

class Offer(
    @ElementCollection
    @CollectionTable(name = "offer_salaries", joinColumns = @JoinColumn(name = "offer_id"))
    @OrderColumn
    @Column(name = "salaries")
    val salaries: List<Salary>;
)

Answer 1

@OneToMany is meant for when you want to map to a db table as an entity. @ElementCollection : you can look at it as a regular collection which is used for mapping non-entities.

ref: Difference between @OneToMany and @ElementCollection?

EG: you have a Perfume entity and it has 2 lists.

• scents - is a list of attribues (should be @ElementCollection ) since it contains some attributes which are not entities.
• customers - is a list of entities (should be @oneToMany since it should be mapped as an entity)