[FIXED] JPA @OneToMany : foreign key is null

Issue

I need help to define correctly a @OneToMany JPA annotation. Tried different ways but still get error/issues like the foreign key (visitor_revision_id) is null in the visitorCharacteristic table.

I would like to join the 2 tables with the "visitor_revision_id"

@Entity
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="id")
@ToString
public class Visitor {
    @Id
    @Column(name="visitor_revision_id")
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    Long id;

    String visitorCode;

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "visitor")
    List<VisitorCharacteristic> visitorCharacteristicList;
}

@Entity
@JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="id")
@ToString
class VisitorCharacteristic {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    Long id;

    @JoinColumn(name = "visitor_revision_id")
    @ManyToOne(optional = false) //fetch = FetchType.EAGER, cascade =  CascadeType.ALL)
    Visitor visitor;

    @Column(nullable = false)
    String attributeCode;

    @Column(nullable = false)
    String attributeValue;    
}

Thanks in advance for your help

Solution

JPA will not set VisitorCharacteristic#visitor field for you, you have to do it manually. If you have some method for adding subsequent VisitorCharacteristics, you should add the code for setting visitor in characteristic as well:

public void addVisitorCharacteristic(VisitorCharacteristic visitorCharacteristic) {
    if (visitorCharacteristicList == null) {
        visitorCharacteristicList = new ArrayList<>();
    }
    visitorCharacteristic.visitor = this;
    visitorCharacteristicList.add(visitorCharacteristic);
}

Here you can find a Gist with your code which works well - look at the line 79.

Answered By - Maciej Dobrowolski