CODEWITHSUNDEEP
javahibernatejpajakarta-eemany-to-many
Zon
Zon

Reputation: 19918

JPA ManyToMany List is Empty

PROBLEM: My entity list is empty after binding to Postgres table.

RESEARCH: JavaEE7, Java8, JPA2.1. OneToMany for this entity and similar ManyToMany binded fields in other entities work fine with the same database.

Table 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);

Entity:

@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:
}

I create entity in REST-service like:

IndicatorType indicatorType = comparisonDao.getIndicatorTypeById(1);

And get enter image description here

QUESTION: Any ideas of what is missed to make it work. What else is required from code?

Upvotes: 0

Views: 1920

Answers (2)

Zon
Zon

Reputation: 19918

As expected, it was a simple typo-error 34+ viewers have also missed. I've tried to add parameter to annotation:

@ManyToMany(mappedBy = "")

and asked Intellij for suggestions in double quotes. Suprisingly it has suggested fields from another entity - RegionType. The error was in the list type:

private List<RegionType> reportTypes;
-> private List<ReportType> reportTypes;

Upvotes: 0

Rishikesh Meena
Rishikesh Meena

Reputation: 61

Cascading is missing. Below is the example :

@ManyToMany(
        cascade = {CascadeType.ALL},
        fetch = FetchType.LAZY
    )
    @JoinTable(
        name = "report_type_to_indicator_type",
        joinColumns = {@JoinColumn(name = "indicator_type_id")},
        inverseJoinColumns = {@JoinColumn(name = "report_type_id")}
    )
    private List<RegionType> reportTypes;

Upvotes: 1

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