Jpa ManytoMany issue with Spring Boot - spring

Question

I have a postgres database and I am trying to make a simple REST service with Spring Boot. I have a problem with jpa ManytoMany relationship.
Person Entity:
#Entity
#Table(name = "person", schema = "persons")
public class Person implements Serializable {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
private Integer id;
#Column(nullable = false)
private String name;
#Column(nullable = false)
private String email;
#Column
private Integer age;
#ManyToOne
#JoinColumn(name = "country_id", referencedColumnName = "id")
private Country countryOfBirth;
#ManyToMany
#JoinTable(
name="persons_countries_residence",
joinColumns=#JoinColumn(name="person_id", referencedColumnName="id"),
inverseJoinColumns=#JoinColumn(name="country_id", referencedColumnName="id"))
private List<Country> countriesOfResidence;
// getters and setters and to String method overriden
}
Country Entity:
#Entity
#Table(name = "country", schema = "persons")
public class Country implements Serializable {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
private Integer id;
#Column(name = "country_name")
private String name;
#Column(name = "country_code")
private String code;
// getters and setters and to String method overriden
}
The postgres schema is the following:
Person Table:
CREATE TABLE persons.person
(
id serial NOT NULL,
name character varying(50) NOT NULL,
email character varying(40) NOT NULL,
age integer,
country_id serial NOT NULL,
CONSTRAINT id PRIMARY KEY (id),
CONSTRAINT country_id FOREIGN KEY (id)
REFERENCES persons.country (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION
)
Country table:
CREATE TABLE persons.country
(
id serial NOT NULL,
country_name character varying(45) NOT NULL,
country_code character varying(10) NOT NULL,
CONSTRAINT country_id PRIMARY KEY (id)
)
Join table:
CREATE TABLE persons.persons_countries_residence
(
person_id integer NOT NULL,
country_id integer NOT NULL,
CONSTRAINT person_country_id PRIMARY KEY (person_id, country_id),
CONSTRAINT persons_countries_residence_country_id_fkey FOREIGN KEY (country_id)
REFERENCES persons.country (id) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE NO ACTION,
CONSTRAINT persons_countries_residence_person_id_fkey FOREIGN KEY (person_id)
REFERENCES persons.person (id) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE CASCADE
)
When i make an HTTP method call, I don't get the Countries of residence.
Service code:
#RequestMapping(method = RequestMethod.GET, produces = {MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE})
public List<Person> getAllPersons() {
retutn jpaPersonRepository.findAll();
}
Any help appreciated.

Answer 1

Maybe, you need to specify a schema name in the join table name:
#JoinTable(
name="persons_countries_residence", schema="persons",
joinColumns=#JoinColumn(name="person_id", referencedColumnName="id"),
inverseJoinColumns=#JoinColumn(name="country_id", referencedColumnName="id"))

Answer 2

Update your Country class code like :
#Entity
#Table(name = "country", schema = "persons")
public class Country implements Serializable {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
private Integer id;
#Column(name = "country_name")
private String name;
#Column(name = "country_code")
private String code;
#ManyToMany(mappedBy = "countriesOfResidence")
private List<Person> persons;
// getters and setters and to String method overriden
}
Although a ManyToMany relationship is always bi-directional on the
database, the object model can choose if it will be mapped in both
directions, and in which direction it will be mapped in. If you choose
to map the relationship in both directions, then one direction must be
defined as the owner and the other must use the mappedBy attribute to
define its mapping. This also avoids having to duplicate the JoinTable
information in both places.

Answer 3

Do you mean that the country list is null? #ManyToMany associations are lazily loaded by default, you need to enable eager-fetching for it to work straight away.
#ManyToMany(fetch = FetchType.EAGER)

Answer 4

The solution is this:
#ManyToMany
#JoinTable(
name="persons_countries_residence", schema = "persons",
joinColumns=#JoinColumn(name="person_id", referencedColumnName="id"),
inverseJoinColumns=#JoinColumn(name="country_id", referencedColumnName="id"))
private List<Country> countriesOfResidence;
The schema had to be specified at the #JoinTable annotation as well.