JSON returns 一个字段有 ID，另一个字段有完整的对象，当两个对象相同时

Question

我有一个 class 如下所示。

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode
@Entity
@Table( name = "hires", indexes = { @Index( name = "idx_hire_date", columnList = "date DESC" ) }, uniqueConstraints = {
    @UniqueConstraint( columnNames = { "vehicle_id", "po_number" } ) } )
@DynamicUpdate
@JsonIdentityInfo( generator = ObjectIdGenerators.PropertyGenerator.class, property = "id" )
public class Hire implements Serializable {

@Id
@GeneratedValue( strategy = GenerationType.IDENTITY )
int id;

@OneToOne( targetEntity = Driver.class, fetch = FetchType.EAGER )
@JoinColumn( name = "pass_payer", referencedColumnName = "id", nullable = true )
Driver passPayer;

@OneToOne( targetEntity = Driver.class, fetch = FetchType.EAGER )
@JoinColumn( name = "driver_id", referencedColumnName = "id", nullable = true )
Driver driver;
...
}

我通过 Rest 端点获取此对象。问题是当字段 passPayer 和 driver 对象相等时，在返回的 JSON 中，driver 字段仅包含 ID（这只是一个整数值）并且 passPayer 字段包含所有对象字段。

"passCost": 300.0,
        "passPayer": {
            "id": 9,
            "firstName": "XXXX",
            "lastName": "XXXXXX",
            "idNo": "000000000000"
        },
        "driver": 9,
        "driverSalary": xxxx.xx,

当这些字段具有不同的对象时，两个字段都会显示如下所示的完整详细信息。

"passCost": 300.0,
        "passPayer": {
            "id": 9,
            "firstName": "XXXX",
            "lastName": "XXXXXX",
            "idNo": "000000000000"
        },
        "driver": {
            "id": 4,
            "firstName": "YYYYYY",
            "lastName": "YYYYYYY",
            "idNo": "10101010101"
        },
        "driverSalary": 00000.00,

我需要两个对象都包含数据（字段。[id, firstName, lastName, idNo]），无论它们是否相等。

感谢任何线索！

Answer 1

这是@JsonIdentityInfo( generator = ObjectIdGenerators.PropertyGenerator.class, property = "id" )造成的，检查docs。引用:

Annotation used for indicating that values of annotated type or property should be serializing so that instances either contain additional object identifier (in addition actual object properties), or as a reference that consists of an object id that refers to a full serialization.

由于两个字段都引用同一个对象，因此第二个字段被序列化为对第一个对象的引用。

根据我的经验，这个注解多用于处理循环引用，所以你可以：

删除它，如果你的用例允许它（对象中没有循环引用）
或者您可以使用 DTO（无论如何这是首选方法）

JSON returns 一个字段有 ID，另一个字段有完整的对象，当两个对象相同时

JSON returns one field with ID and other field with full object, when both objects are same

java

json

spring-boot

rest

jackson-databind