Hibernate: org.hibernate.LazyInitializationException: Failed to lazily initialize role collection: session or session closed

I will learn to hibernate. But I am stuck at a very simple point.

When the source is next

    Controller : data collection and ready to display 
    Service : Transaction processing
    Dao : access Database 

      

        
        
        
      

    

And data processing in this form.

Test.java

@Entity
@Table ( name = "table_test" )
public class Test
{

    @Id
    @GeneratedValue ( strategy = GenerationType.AUTO )
    public long id;

    @OneToMany(fetch=FetchType.LAZY)
    @JoinColumn(name="test_id")
    @IndexColumn(name="orderBy")
    public List<TestItem> items;

}

      

        
        
        
      

    

TestItem.java

@Entity
@Table ( name = "table_item" )
public class TestItem
{

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="test_id", insertable=false, updatable=false)
    public Test parent;

    @Id
    @GeneratedValue ( strategy = GenerationType.AUTO )
    public long id;

}

      

        
        
        
      

    

TestDao.java

@Repository
public class TestDao
{

    @Autowired SessionFactory sessionFactory;

    protected Session getSession(){
        return sessionFactory.getCurrentSession();
    }

    public Test get(long id){
        return (Test) getSession().createCriteria( Test.class )
                    .add( Restrictions.eq( "id", id ) ).uniqueResult();
    }
}

      

        
        
        
      

    

TestService.java

@Service
@Transactional
public class TestService
{

    @Autowired
    TestDao testd;

    public Test get(long id){
        return testd.get( id );
    }

    public List<TestItem> getItems(Test test){
        List<TestItem> items = test.items;
        items.iterator();
        return items;
    }

}

      

        
        
        
      

    

TestController.java

@Controller
@RequestMapping ( "/test" )
public class TestController extends BaseController
{
    @Autowired
    TestService testService;

    @RequestMapping ( "/{id}" )
    public String seriesList ( @PathVariable long id, Model model )
    {
        Test test = testService.get( id );

        //something...

        List<TestItem> lists = testService.getItems( test );

        for(TestItem item : lists)
        {
            Model.addAttribute(item.id);
        }

        return "index";
    }
}

      

        
        
        
      

    

AN EXCEPTION

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.test.domain.Test.items, no session or session was closed
    org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383)
    org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375)
    org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368)

      

        
        
        
      

    

For what reason, if I am using Lazy.

This is because it cannot be used by the Something list.

I know how to get around some.

1) The first solution is "already a list", but removes the need for lazy.

@Service
@Transactional
public class TestService
{

    @Autowired
    TestDao testd;

    public Test get(long id){
        Test test = testd.get( id );
        test.items.iterator();
        return test;
    }

    public List<TestItem> getItems(Test test){
        List<TestItem> items = test.items;
        items.iterator();
        return items;
    }

}

      

        
        
        
      

    

2) the second solution is "a process by an internal transaction", but this solution is used, it is always executed in a transaction

@Controller
@RequestMapping ( "/test" )
public class TestController extends BaseController
{
    @Autowired
    TestService testService;

    @RequestMapping ( "/{id}" )
    public String seriesList ( @PathVariable long id, Model model )
    {
        return testService.view( id, model );
    }
}
@Service
@Transactional
public class TestService
{

    @Autowired
    TestDao testd;

    public Test get(long id){
        Test test = testd.get( id );
        return test;
    }

    public String view(long id, Model model){
        Test test = get( id );

        List<TestItem> lists = test.items;

        for(TestItem item : lists)
        {
            model.addAttribute( item.id );
        }

        return "index";
    }

}

      

        
        
        
      

    

There seem to be several problems.

So, I only want to educate when necessary.