JPA多人列表为空

问题:绑定到Postgres表后,我的实体列表为空。

表DDL:

create table clean.report_type_to_indicator_type(
indicator_type_id integer not null
    constraint report_type_to_indicator_type_indicator_type_id_fk
        references indicator_type,
report_type_id integer not null
    constraint report_type_to_indicator_type_report_type_id_fk
        references report_type,
constraint report_type_to_indicator_type_pk
    primary key (indicator_type_id, report_type_id)
);

create unique index 
report_type_to_indicator_type_indicator_type_id_report_type_id_
on clean.report_type_to_indicator_type (indicator_type_id, 
report_type_id);

实体

@Entity
@Table(schema = "clean")
@JsonIgnoreProperties(ignoreUnknown = true)
public class IndicatorType {

  // Fields:

  @Id @GeneratedValue private int id;
  private String name;

  @ManyToOne private Unit unit;

  @ManyToOne private PeriodType periodType;

  @ManyToOne private RegionType regionType;

  @ManyToMany
  @JoinTable(
      schema = "clean",
      name = "report_type_to_indicator_type",
      joinColumns = @JoinColumn(name = "indicator_type_id"),
      inverseJoinColumns = @JoinColumn(name = "report_type_id"))
  private List<RegionType> reportTypes;

  // Getters and setters:
}

我在REST服务中创建实体,如:

IndicatorType indicatorType = comparisonDao.getIndicatorTypeById(1);

问题:有没有什么想法可以让它发挥作用。代码还需要什么?