使用给定的字段对象id存储JPA实体而不是对象本身

Question

The problem is following:

We have entity:

@Entity
public class Feedback {
    @Id
    @GeneratedValue(generator="token")
    private String id; 

    @ManyToOne
    private Product product;

    private String message;

    // other fields
}

And we have a server endpoint, that receives feedback from clients. Feedback received in multipart/form-based format, with fields:

 ProductId - product identifier
 Message - feedback message
 Some other fields

To set Feedback.product we need to load Product object from JPA - this can be time-consuming and it creates unnecessary queries.

Is it possible to store entity, but pass the product id instead of the product object? We need some way to modify the INSERT query.

We use EclipseLink JPA with Spring and Vaadin.

Answer 1

使用EntityManager.getReference() ：如果实体尚未加载，它只是在ID周围创建一个延迟初始化的代理，而不会导致执行任何SQL查询。