I'm using Spring 3.2.9 with multilayered architecture design broken down to 3 modules web, service, repository. In repository i defined a generic DAO class which i inherit by other entity specific DAO classes.
The problem is that when i try to lazy fetch collection of my entity from service layer, I always get LazyInitializationException. I have tried putting @Transactional on my service class, but It appears to not work. I can only avoid exception if I initialize all lazy collections right away in the DAO class method (and only if i annotate DAO class with @Transactional), but I want to fetch those collections only when they are needed in bussiness logic, and not all in advance.
Strange thing is that @Transactional works only in DAO layer, but not in Service layer, where it should be used. I found a couple of ways to work around this issue, but I am interested to really underestend and solve this issue, and not only make make code work.
repository MODULE:
@Repository
public abstract class GenericDao<T> {
protected Class<T> entityClass;
@PersistenceContext
protected EntityManager entityManager;
.........
public T findById(long id) {
T entity = entityManager.find(entityClass, id);
if (entity == null) {
throw new EntityNotFoundException(entityClass.getSimpleName(), id);
}
return entity;
}
}
My service class in service MODULE:
@Service
public class UserServiceImpl implements UserService {
private UserDao userDao;
@SuppressWarnings("SpringJavaAutowiringInspection")
@Autowired
public UserServiceImpl(UserDao userDao) {
this.userDao = userDao;
}
@Transactional(readOnly = true)
@Override
public UserDto getUserById(long id) {
User user = userDao.findById(id);
return new UserDto(user);
}
The DTO constructor tries to access user.getTeams() and then exception occurs. Instead of that, collection should be fetched with additional query to DB.
CONFIGURATION:
repository configuration: ......some other configurations like datasource...
<!--EntityManagerFactory-->
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="persistenceXmlLocation" value="classpath:./META-INF/persistence.xml"/>
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
</property>
<property name="jpaPropertyMap">
<map>
<entry key="hibernate.dialect" value="${hibernate_dialect}"/>
<entry key="hibernate.hbm2ddl.auto" value="${hibernate_Hbm2ddlAuto}"/>
<entry key="hibernate.show_sql" value="${hibernate_showSql}"/>
<entry key="hibernate.format_sql" value="${hibernate_formatSql}"/>
</map>
</property>
</bean>
persistence.xml:
<persistence-unit name="persistenceUnit">
...other classes..
<class>com.example.entity.User</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
</properties>
</persistence-unit>
service configuration:
<import resource="classpath*:META-INF/repositoryApplicationContext.xml"/>
<tx:annotation-driven/>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory"/>
</bean>
