One to Many Relation mapping using org.mapstruct framework

Question

How can I map the one to many relationship using org.mapstruct framework?

DTO classes:

@Data
public class ScheduledJobDTO {

    private String jobName;
    private String jobGroup;
    private String jobClass;
    private String cronExpression;
    private Boolean cronJob;
    private Long repeatTime;
    private Integer repeatCount;
    private Set<ScheduledJobParamsDTO> paramtersDTOs;

}

@Data
@EqualsAndHashCode
public class ScheduledJobParamsDTO {

    String name;
    String value;
}

Domain Classes -

@Data
@Entity
@Table(name = "scheduled_job")
public class ScheduledJob {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "job_name")
    private String jobName;
    @Column(name = "job_group")
    private String jobGroup;
    @Column(name = "job_class")
    private String jobClass;
    @Column(name = "cron_expression")
    private String cronExpression;
    @Column(name = "is_cron_job")
    private Boolean cronJob;
    @Column(name = "repeat_time")
    private Long repeatTime;
    @Column(name = "repeat_count")
    private Integer repeatCount;
    @Column(name = "trigger_start_date")
    private LocalDate triggerStartDate;
    @Column(name = "trigger_end_date")
    private LocalDate triggerEndDate;
    @Column(name = "created_at")
    private LocalDate createdAt;
    @Column(name = "modified_at")
    private LocalDate modifiedAt;
    @Column(name = "is_active")
    private Boolean active;
    @OneToMany(mappedBy = "scheduledJob")
    private Set<ScheduledJobParams> parameters;

}

@Data
@Entity
@Table(name = "scheduled_job_params")
@EqualsAndHashCode
public class ScheduledJobParams {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    Long id;
    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "scheduled_job_id", nullable = false)
    ScheduledJob scheduledJob;
    String name;
    String value;
}

Mapper Class -

@Mapping(source = ".", target = ".")
@Mapping(source = "paramtersDTOs", target = "parameters")
ScheduledJob mapToDomain(ScheduledJobDTO scheduledJobDTO);

Now, the above mapper is mapping the ScheduledJob & ScheduledJobParams, but the ScheduledJobParams has reference of ScheduledJob.

How can I map the reference ScheduledJob to ScheduledJobParams?

score 0 · Accepted Answer · answered Nov 05 '20 at 14:44

You can achieve that through @AfterMapping with @MappedTarget. This is described in the reference documentation: 12.2. Mapping customization with before-mapping and after-mapping methods.

// Java 8+ otherwise you need to use an abstract class and a for-loop instead
@Mapper(componentModel = "spring")
public interface ScheduledJobMapper {

    @Mapping(target = "parameters", source = "paramtersDTOs")
    ScheduledJob mapToDomain(ScheduledJobDTO dto);

    @AfterMapping
    default void after(@MappingTarget ScheduledJob domain, ScheduledJobDTO dto) {
        domain.getParameters().forEach(scheduledJobParams -> {
            scheduledJobParams.setScheduledJob(domain);
        });
    }
}

However, I am sure you don't need to fill the bidirectional relationship when you map back from the DTO into the entity (this is what I understand as you refer to "domain"). Note printing out or serializing such object i.e. into JSON or XML throws java.lang.StackOverflowError if not properly handled.

One to Many Relation mapping using org.mapstruct framework

1 Answers1