Spring Data JPA Hibernate - Extra elements appearing in #ManyToOne relationship - spring

Question

I have some entity classes which have a one-to-many - many-to-one relationship. I am using Spring and Hibernate.
Each TwoWayService has exactly 2 Services in my application.
Excerpts:
#Entity
#Table(name = "two_way_services")
public class TwoWayService {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#Column
private String name;
#OneToMany(cascade = CascadeType.ALL,
mappedBy = "twoWayService",
fetch = FetchType.EAGER)
private List<Service> services;
public TwoWayService() {
services = new ArrayList<>();
// Add two as default
services.addAll(Arrays.asList(new Service(), new Service()));
}
public void setService1(Service service) {
services.set(0, service);
service.setTwoWayService(this);
}
public void setService2(Service service) {
services.set(1, service);
service.setTwoWayService(this);
}
...
}
#Entity
#Table(name = "services")
public class Service {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
#Column
private String name;
#ManyToOne(optional = false)
#JoinColumn
private TwoWayService twoWayService;
public void setTwoWayService(TwoWayService twoWayService) {
this.twoWayService = twoWayService;
}
...
}
I am using Derby on the backend. The database schema is like this:
CREATE TABLE two_way_services (
id INT NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
config_name VARCHAR(255) NOT NULL,
name VARCHAR(80),
admin_ip VARCHAR(32) NOT NULL,
connection_state INT NOT NULL
);
CREATE TABLE services (
id INT NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
name VARCHAR(80),
type INT NOT NULL,
ruleset VARCHAR(255) NOT NULL,
two_way_service_id INT,
FOREIGN KEY (two_way_service_id) REFERENCES two_way_services(id) ON DELETE CASCADE
);
The repository interface:
public interface TwoWayServiceRepository extends Repository<TwoWayService, Integer> {
<S extends T> S save(S entity);
...
}
In my unit tests, I find that when I call findOne on a TwoWayService, I find that I have 4 Services instead of 2. Browsing the database directly shows the data as I would expect.
TwoWayService tws1 = repo.findOne(1); // get by id
assertThat(tws1.getServices().size()).isEqualTo(2); // fails, expected:<[2]> but was:<[4]>
Examining it in the debugger I see 4 elements in the services list: the two that I expect, plus 2 extra ones which are copies of the expected. I don't see where these are coming from. Why are these extra objects appearing in the list?

Answer 1

I am not sure but I think, it is because you add 2 services in the constructor and 1 in each setter. This makes 4 in total. You test for the amount of services, is that what you wanted to test?