java - 将 hibernate 实体转换为 JSON : oblectId instead of whole object

Question

项目有两个实体:

@Entity
public class Customer {
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id", unique = true, nullable = false)
private Integer id;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "city_id", nullable = true)
private City city;
...
}

和

@Entity
public class City {
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id", unique = true, nullable = false)
private Integer id;

@Column(name = "name", nullable = false)
private String name;
...
}

使用 Gson 或 Jackson 转换为 JSON 的客户实体

{
"id":1,
"city":{"id":1, "name":"New York"}
}

我希望它转换为

{
"id":1,
"city_id":1
}

我如何通过 gson 或 jackson 做到这一点？

Answer 1

这个问题可能对你有帮助。

Gson: How to exclude specific fields from Serialization without annotations

我不知道是否有直接的方法来实现这一点，但有一些间接的方法可以做到这一点。例如，您可以将 private City city 标记为 transient，然后您可以公开另一个名为 city_id 的字段，该字段只是城市 ID。它看起来像这样:

@Entity
public class Customer {
    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "city_id", nullable = true)
    private transient City city;

    private int city_id;
    ...
}