Better solution to avoid "org.hibernate.LazyInitializationException: could not initialize proxy - no Session" in Lazy model

Question

"Tipo" has one "Profissão:"

@ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "id_profissao", nullable = false)
    public Profissao getProfissao() {
    return profissao;
    }

When I tried to in datatable view data of a relation entities Tipo and Profissao related:

  <p:dataTable var="lista" value="#{tipoBean.tipos}" id="tabelaTipos"
            rows="10" paginator="true" widgetVar="tabelaTipos">

            <p:column headerText="Profissão">
                <h:outputText value="#{lista.profissao.nome}" />


</p:dataTable>

DAO:

 Criteria cri = session.createCriteria(Tipo.class)
                     .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY)
                     .addOrder(Order.asc("nome"));

  return cri.list();

I got this error widely discussed here: org.hibernate.LazyInitializationException: could not initialize proxy - no Session

So I implemented this using "Hibernate.initialize" way.

Criteria cri = session.createCriteria(Tipo.class)
                     .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY)
                     .addOrder(Order.asc("nome"));

            List<Tipo> tipos = (List<Tipo>) cri.list();

            for (Tipo t :tipos) {
                Hibernate.initialize(t.getProfissao()); 

            }

It worked but there's a better solution to it? I don't wanna use Eager solution. Any solutions?

Thanks!

Try using session.setFetchMode("profissao", FetchMode.JOIN); and let me know — geoand
– geoand, Commented Aug 11, 2014 at 18:21
@geoand it worked but using this is not the same as doing relationship like EAGER? When I tried to apply this solution where one item have a many entities related I get this error: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags. — gustavomr
– gustavomr, Commented Aug 11, 2014 at 18:54
It's not the same as using eager. It tells hibernate to construct a join query as opposed to using extra queries that eager forces. But yes what you mentioned with the multiple relationships wont work — geoand
– geoand, Commented Aug 11, 2014 at 19:13
@geoand thanks for your reply! So, I want to know how to do it in the right way. I searched and i'm not getting the right way... — gustavomr
– gustavomr, Commented Aug 11, 2014 at 19:25
I've written a basic Hibernate tutorial that you might find helpful. I give you ways to get around the no session/lazy initialisation error. You can find it here — JamesENL
– JamesENL, Commented Aug 12, 2014 at 3:47

Maarten Winkels · Accepted Answer · 2014-08-12 01:50:24Z

1

First you need to determine what day you need for the page/table. This data needs to be fetched from the db by hibernate somehow, be it by join or separate select or query.

Now you have two options:

Fetch the data in you service layer before returning the object to the view layer. For this you can specify FetchModes (join or select) on your query or use Hibernate.initialize.
Use an open-session in view strategy. With this solution the view can load additional data by traversing the object model. If an association was previously not loaded, but the view invokes the getter, hibernate will initialize the proxy.

Second option Pro: more flexible: if you need more data in the view later on, you don't need to change the service layer. This is because the service layer head no knowledge of what data is used. Con: it is harder to find performance problems: since the view loads data when necessary, the bulk of the data might be loaded after your service layer has done its job. Measuring response times in your service layer can often easily bare accomplished by adding an interceptor. Depending on you view technology, measuring rendering time might be much harder.

answered Aug 12, 2014 at 1:50

Maarten Winkels

2,41716 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

gustavomr Over a year ago

thanks. Using option 1 in fetchmode (join) I got few queries than "Hibernate.initialize" but my problem is where an entitie has to load (join) with more than one entitie I got this error org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags.

Maarten Winkels Over a year ago

Only one OneToMany association with FetchMode.Join is allowed. If you really need to fetch multiple collections, you'll have to resort to FetchMode.Select for all but one. This will result in n+1 selection problems.

Collectives™ on Stack Overflow

Better solution to avoid "org.hibernate.LazyInitializationException: could not initialize proxy - no Session" in Lazy model

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related