I'm using JPA with a table-per-class inheritance strategy (joined inheritance), and I'm encountering a foreign key constraint issue when saving an entity. Below are the details of the problem:

Entities:

Connector is the base entity. SinglePageConnector and DualPageConnector extend Connector and are stored in separate tables (singlepage_connector, dualpage_connector). I have a UserConnector entity that references Connector via a foreign key (connector_id).

create table connector
(
    id                varchar(36)  not null,
    name              varchar(255) not null,
    login_page_url    varchar(255),
    primary key (id)
);

create table singlepage_connector
(
    id            varchar(36)  not null,
    connector_id  varchar(36)  not null,
    primary key (id),
    foreign key (connector_id) references connector(id)
);

create table dualpage_connector
(
    id                   varchar(36)  not null,
    connector_id         varchar(36)  not null,
    next_button_selector varchar(36),
    primary key (id),
    foreign key (connector_id) references connector(id)
);

create table user_connector
(
    id           varchar(36)  not null,
    user_id      varchar(36)  not null,
    connector_id varchar(36)  not null,
    username     varchar(255) not null,
    PRIMARY KEY (id),
    CONSTRAINT unique_user_connector UNIQUE (user_id, connector_id),
    FOREIGN KEY (connector_id) references connector (id)
)

JPA entity code

@Entity
public class Connector { 
    @OneToMany(mappedBy = "connector")
    private Set<UserSwaConnector> userSwaConnectors;
}

@Entity
public class SinglePageConnector extends Connector { ... }

@Entity
public class DualPageConnector extends Connector { ... }

@Entity
public class UserConnector {
    @ManyToOne
    @JoinColumn(name = "connector_id", referencedColumnName = "id")
    private Connector connector;
    ...
}

Issue

When I try to save a UserConnector like this:

UserConnector connector = UserConnector.builder()
    .username(command.getConnectorUsername())
    .userId(command.getUserId())
    .connector(connector)
    .build();

userSwaConnectorRepository.save(connector);

I encounter the following error:

Cannot add or update a child row: a foreign key constraint fails (authorization.user_connector, CONSTRAINT user_connector_ibfk_1 FOREIGN KEY (connector_id) REFERENCES connector (id))

The error occurs because JPA is trying to insert the foreign key reference (connector_id) into the parent connector table, but the actual data is in one of the child tables (singlepage_connector or dualpage_connector). Since UserConnector references Connector, which is an abstract base class, JPA does not correctly search in the child tables for the foreign key.

What I want to do:

I want JPA to search for the connector_id in the appropriate child table (singlepage_connector or dualpage_connector) instead of the parent connector table, since the actual data is stored in those child tables.

How can I configure JPA to properly handle this foreign key relationship, considering that the actual data resides in the child tables?