JPA, Spring, Hibernate problem with loading entities ManyToMany Assotiation

Question

I'm trying to get data from assotiation N:N, but I receive blank field.
There are my Hibernate mapping class:

@Entity
@Table(name = "companies")
public class Company extends NamedEntity {
 //some_code

@ManyToMany(
        targetEntity = com.hqcargo.shippingstock.domain.CompanyProfile.class,
        cascade = {CascadeType.ALL, CascadeType.ALL },
        fetch = FetchType.EAGER
        )
@JoinTable(
        name = "company_company_profiles",
        joinColumns = {@JoinColumn(
                        name = "company_id",
                        referencedColumnName = "id") },
        inverseJoinColumns = {@JoinColumn(
                        name = "company_profile_id",
                        referencedColumnName = "id") }
        )
private List<CompanyProfile> profiles;
// getters and setters + other code

other class:

@Entity
@Table(name = "company_profiles")
public class CompanyProfile extends NamedEntity {
//some_code
@ManyToMany(
        targetEntity = com.hqcargo.shippingstock.domain.Company.class,
        cascade = {CascadeType.ALL, CascadeType.ALL }, 
        mappedBy = "profiles",
        fetch = FetchType.EAGER
        )
@JoinTable(
        name = "company_company_profiles",
        joinColumns = {@JoinColumn(
                        name = "company_profile_id",
                        referencedColumnName = "id") },
        inverseJoinColumns = {@JoinColumn(
                        name = "company_id",
                        referencedColumnName = "id") }
        )
 private List<Company> companies;
 // getters and setters + other code

This classes works fine with saving but not with loading data.
Below I add DAO class:

public class CompanyJpaDAO extends JpaDaoSupport
implements CompanyDAO {

@Transactional(readOnly = true)
public Company readById(Long id) {
    Company tempCompany = getJpaTemplate().find(Company.class, id);
    return tempCompany;
    }
}

@Transactional
public void update(Company existingInstance) {
    if (existingInstance.isNew()) {
        throw new InvalidDataAccessApiUsageException(
            "Can't update record. Given instance don't have assigned ID");
    }
    save(existingInstance);
}

when I update every is ok (generated sql by Hibernate):

251252 [13627369@qtp-8132032-9] DEBUG org.hibernate.SQL  -
update
    companies
set
    name=?,
where
    id=?
Hibernate:
update
    companies
set
    name=?,
where
    id=?
251295 [13627369@qtp-8132032-9] DEBUG org.hibernate.SQL  -
insert
into
    company_company_profiles
    (company_id, company_profile_id)
values
    (?, ?)
Hibernate:
insert
into
    company_company_profiles
    (company_id, company_profile_id)
values
    (?, ?)

but when I load data i don't get info from company_company_profiles (sql generated by Hibernate)

36088 [13507994@qtp-8132032-13] DEBUG org.hibernate.SQL  -
select
    companies0_.company_profile_id as company2_8_,
    companies0_.company_id as company1_8_,
    company1_.id as id3_0_,
    company1_.name as name3_0_,
from
    company_company_profiles companies0_
left outer join
    companies company1_
        on companies0_.company_id=company1_.id
where
    companies0_.company_profile_id=?
Hibernate:
select
    companies0_.company_profile_id as company2_8_,
    companies0_.company_id as company1_8_,
    company1_.id as id3_0_,
    company1_.name as name3_0_,
from
    company_company_profiles companies0_
left outer join
    companies company1_
        on companies0_.company_id=company1_.id
where
    companies0_.company_profile_id=?

Do you see any mistakes in my code?

Answer 1

I'm not sure this is the cause of the problem but you are not supposed to specify a JoinTable on both sides of your many-to-many association. As per the JPA specification, the JoinTable annotation goes on the the owning side of the association (Company in your case):

9.1.25 JoinTable Annotation

The JoinTable annotation is used in the mapping of associations. A JoinTable annotation is specified on the owning side of a many-to-many association, or in a unidirectional one-to-many association.

So remove it in the CompanyProfile entity:

@Entity
@Table(name = "company_profiles")
public class CompanyProfile extends NamedEntity {
    //some_code
    @ManyToMany(
        targetEntity = com.hqcargo.shippingstock.domain.Company.class,
        cascade = {CascadeType.ALL, CascadeType.ALL }, 
        mappedBy = "profiles",
        fetch = FetchType.EAGER
    )
    private List<Company> companies;
    // getters and setters + other code
}

And try again.

References

• JPA 1.0 specification
  • Section 2.1.8.4 "Bidirectional ManyToMany Relationships"
  • Section 9.1.25 "JoinTable Annotation"
  • Section 9.1.26 "ManyToMany Annotation"