Spring Data Jpa - could not initialize proxy - no Session

Witam.

W mojej aplikacji wykorzystuję Spring Data JPA wraz ze Hibernatem. Po zmianie z

@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.MERGE, mappedBy = "owner")
@OrderBy("id ASC")
private Set<Unit> units;

na

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.MERGE, mappedBy = "owner")
@OrderBy("id ASC")
private Set<Unit> units;

dostaję błąd could not initialize proxy - no Session

Klasa DAO:

@Repository
public interface PlayerDAO extends JpaRepository<Player, Integer>
{
    @Query("select g from Player g, PlayerData gd where g.playerData = gd and gd.login = ?1")    
    Player findByLogin(String login);
}

Metoda z serwisu, w której powstaje błąd:

@Override
    @Transactional
    public DashboardViewModel getDashboardViewModel()
    {
        Subject subject = SecurityUtils.getSubject();
        String login = (String) subject.getPrincipal();

        Player player = graczDAO.findByLogin(login);

       (...)

        int numberOfUnits = player.getUnits().size(); <------ TU POJAWIA SIĘ BŁĄD

       (...)
        return viewModel;
    }

Konfiguracja Springa:

<jee:jndi-lookup id="dataSource" jndi-name="jdbc/__default" />
    
    <bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
        <property name="database" value="MYSQL" />
        <property name="showSql" value="true" />
        <property name="generateDdl" value="true" />
    </bean>
    
    <bean id="transactionManager" class="org.springframework.transaction.jta.JtaTransactionManager" />
    <tx:annotation-driven transaction-manager="transactionManager"/>    

Persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="IslandPU" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <jta-data-source>java:comp/DefaultDataSource</jta-data-source>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
      <property name="hibernate.transaction.jta.platform" value="org.hibernate.service.jta.platform.internal.SunOneJtaPlatform"/>
      <property name="hibernate.show_sql" value="true"/>
      <property name="hibernate.format_sql" value="true"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
      <property name="javax.persistence.schema-generation.database.action" value="none"/>
    </properties>
  </persistence-unit>
</persistence>

Jak rozwiązać ten problem bez wracania do FetchType.EAGER?

Zmienić

@Query("select g from Player g, PlayerData gd where g.playerData = gd and gd.login = ?1")

na

@Query("select g from Player g join PlayerData gd join fetch g.units gu where gd.login = ?1")