Error org.hibernate.Lazyinitializationexception

Question

Error when the drive class is filled with data in the database, if there is no record, I can access my xhtml normally. In the class I count with fetch = Fetchtype.EAGER, but in the class drive this error persists, See the relationships:

Bill

@Entity
//@Cacheable
//@Table(uniqueConstraints={@UniqueConstraint(columnNames = { "agencia","numero" })})
public class Conta implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

private String titular;
private String agencia;
private String numero;
private String banco;

@OneToOne
@JoinColumn(unique=true)
private Gerente gerente;

//@Cache(usage=CacheConcurrencyStrategy.TRANSACTIONAL)
@OneToMany(fetch = FetchType.EAGER, mappedBy="conta") 
private List<Movimentacao> movimentacoes;

getters e setters

Movement

@Entity
public class Movimentacao implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

private String descricao;
private Calendar data;
private BigDecimal valor;

@ManyToOne
private Conta conta;

@ManyToMany
@JoinTable(name = "categorias_da_movimentacao",
        joinColumns = @JoinColumn(name="movimentacao_id"))
private List<Categoria> categorias = new ArrayList<Categoria>();

@Enumerated(EnumType.STRING)
@Column(name = "tipo_movimentacao")
private TipoMovimentacao tipoMovimentacao;

getters e setters

Category

@Entity
public class Categoria implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

private String nome;

getters e setters

Error:

16:44:04,872 GRAVE [javax.enterprise.resource.webcontainer.jsf.application] (http-localhost-127.0.0.1-8080-1) Error Rendering View[/movimentacoes.xhtml]: 
javax.el.ELException: /movimentacoes.xhtml: failed to lazily initialize a collection of role: br.com.caelum.financas.modelo.Movimentacao.categorias, no session or session was closed
at com.sun.faces.facelets.compiler.TextInstruction.write(TextInstruction.java:90) [jsf-impl-2.1.7-jbossorg-2.jar:]

...

Caused by: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: br.com.caelum.financas.modelo.Movimentacao.categorias, 
no session or session was closed
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:393) [hibernate-core-4.0.1.Final.jar:4.0.1.Final]

...

16:44:04,924 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/fj25-financas-web].[Faces Servlet]] (http-localhost-127.0.0.1-8080-1) Servlet.service() for servlet Faces Servlet threw exception: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: br.com.caelum.financas.modelo.Movimentacao.categorias, no session or session was closed

...

Answer 1

This error occurs because your category list is with Lazy, you need to initialize your list first before performing an operation.

You will need to create a method of init() in your class Movimentacao. That is the logic you must follow:

 start Transaction 
      Hibernate.initialize(getCategorias());
 end Transaction 

Here are some examples in Soen:

How to load Lazy fetched items from Hibernate/JPA in my controller

Hibernate: best Practice to pull all Lazy Collections

Answer 2

Well I managed to resolve by changing my dao query, where JPQL offers an explicit way to load the relationships through Join along with the fetch clause.

public List<Movimentacao> listaComCategorias() {
    return this.manager.createQuery("select distinct m from Movimentacao m left join fetch m.categorias",
            Movimentacao.class).getResultList();
}