JPA @OneToMany : foreign key is null

Question

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 visit

Answer 1

You can achieve it by annotating as follows:

@RepositoryRestResource(export = false) on VisitorCharacteristicRepository

and creating your own custom controller For VisitorCharacteristic.

For more understanding you can see - https://youtu.be/FRvtVf9sVjs

Answer 2

class Visitor

public class Visitor {
    @Id
    @Column(name = "visitor_revision_id")
    @GeneratedValue
    Long id;

    @Column
    String visitorCode;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "visitor_revision_id", referencedColumnName = "visitor_revision_id")
    List<VisitorCharacteristic> visitorCharacteristicList;
}

VisitorCharacteristic

public class VisitorCharacteristic {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    Long id;

    @Column
    String attributeCode;
    @Column
    String attributeValue;
}

Answer 3

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.

Answer 4

Without a test case showing the failure its difficult to tell.

Here are some things you can try:

1. add , nullable = false to the join column annotation on VisitorCharacteristic

2. set the relationship in both directions Visitor v = new Visitor(); VisitorCharacteristic vc = new VisitorCharacteristic(); v.setVisitorCharacteristicList(Arrays.asList(vc)); vc.setVisitor(v);