仅在json中返回ID，而不是完整实体对象 [英] Return only ID in json instead full entity object

问题描述

在Spring Boot中从RESTful应用程序创建响应时遇到问题.我的实体包含2个子实体属性.

I have a problem with creating response from my RESTful application in Spring Boot. I have entity which contain 2 subentity properties.

@Entity
@EntityListeners(AuditingEntityListener.class)
@Table(name = "attendances")
public class Attendance {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @Version
    @Column(name = "version")
    private long version;

    @CreatedDate
    @Column(name = "date_created")
    private Date dateCreated;

    @LastModifiedDate
    @Column(name = "last_created")
    private Date lastUpdated;

    @ManyToOne
    @JoinColumn(name = "member_id")
    @NotNull
    private Member member;

    @ManyToOne
    @JoinColumn(name = "meeting_id")
    @NotNull
    private Meeting meeting;

getters, setters..
}

当我使用此数据获取JSON时，我总是会获得具有完整的Member和Meeting实体的完整对象.在这种情况下，我只需要成员ID和会议ID.可以使用特定的注释来做到这一点吗?

When I get JSON with this data, I always get full object with full Member and Meeting entities. In this case, I need only member id and meeting id. Is it possible to do that with a specific annotations?

推荐答案

注释解决方案

可以通过对JSON视图使用批注@JsonView

public class View {
    interface Summary {}
}

@Entity
@EntityListeners(AuditingEntityListener.class)
@Table(name = "attendances")
public class Attendance {

    ...

    @JsonView(View.Summary.class)
    @ManyToOne
    @JoinColumn(name = "member_id")
    @NotNull
    private Member member;

    @JsonView(View.Summary.class)
    @ManyToOne
    @JoinColumn(name = "meeting_id")
    @NotNull
    private Meeting meeting;

    ...
}

@RestController
public class ExampleController {

    @JsonView(View.Summary.class)
    @RequestMapping(...)
    public Attendance annotationShowCase() {
        Attendance attendance = // retrieve attendance
        return attendance;
    }
}

因为annotationShowCase()用@JsonView(View.Summary.class)进行了注释，所以返回的Attendance将只公开也用@JsonView(View.Summary.class)进行注释的字段.

Because annotationShowCase() is annotated with @JsonView(View.Summary.class), the returned Attendance will only expose the fields also annotated with @JsonView(View.Summary.class).

此解决方案使用DTO构造:创建一个新类，用于将某些字段暴露给JSON

This solution uses the DTO construct: create a new class which serves the purpose of exposing certain fields to JSON

public class AttendanceSummary {

    private long memberId;
    private long meetingId;

    public AttendanceSummary(Attendance attendance) {
        this.memberId = attendance.getMemberId();
        this.meetingId = attendance.getMeetingId();
    }

    // getters and setters
}

@RestController
public class ExampleController {

    @RequestMapping(...)
    public AttendanceSummary dtoShowCase() {
        Attendance attendance = // retrieve attendance
        return new AttendanceSummary(attendance);
    }
}

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