How to solve the LazyInitializationException when using JPA and Hibernate

Question

I am working on a project for a customer who wants to use lazy initialization. They always get "lazy initialization exception" when mapping classes with the default lazy loading mode.

@JoinTable(name = "join_profilo_funzionalita", joinColumns = {@JoinColumn(name =    "profilo_id", referencedColumnName = "profilo_id")}, inverseJoinColumns = {@JoinColumn(name = "funzionalita_id", referencedColumnName = "funzionalita_id")})
//@ManyToMany(fetch=FetchType.EAGER) - no exceptions if uncommented
@ManyToMany 
private Collection<Funzionalita> funzionalitaIdCollection;

Is there a standard pattern using JPA classes to avoid this error?

Snippets are welcome, thanks a lot for your time.

Answer 1

Hibernate 4.1.6 finally solves this issue: https://hibernate.atlassian.net/browse/HHH-7457

You need to set the hibernate-property hibernate.enable_lazy_load_no_trans=true

Here's how to do it in Spring:

<bean id="entityManagerFactory"
      class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="myDataSource"/>
    <property name="packagesToScan" value="com.mycompany.somepackage"/>
    <property name="jpaVendorAdapter" ref="hibernateVendorAdapter"/>
    <property name="jpaDialect" ref="jpaDialect"/>
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.enable_lazy_load_no_trans">true</prop>
        </props>
    </property>
</bean>

Voila; Now you don't have to worry about LazyInitializationException while navigating your domain-model outside of a hibernate-session (persistence-context in "JPA-speak")