Hibernate 4.3 to 5.2 upgrade - cannot simultaneously fetch multiple bags

Question

Trying to upgrade to hibernate 5.2.9 from 4.3.11. Currently using the hibernate native api. After adding the dependency in pom.xml I get the following error when running my units tests:

Unsatisfied dependency expressed through field 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in class path resource [testApplicationContext.xml]: Invocation of init method failed; nested exception is org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags

I have a testApplicationContext.xml with the following:

<bean id="sessionFactory"
    class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <property name="packagesToScan" value="org.xxxx.xxxx.xxxx.model"/>
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">${hibernate.dialect}</prop>
            <prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.use_sql_comments">true</prop>
            <prop key="hibernate.hbm2ddl.auto">update</prop>
        </props>
    </property>
</bean>

<bean id="transactionManager"
    class="org.springframework.orm.hibernate5.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory" />
</bean>

<tx:annotation-driven transaction-manager="transactionManager" />

I updated the sessionFactory and transactionManager from hibernate4 to hibernate5.

pom.xml:

<dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.2.9.Final</version>
    </dependency>

As far as I can tell, the error message implies that there is an issue loading multiple eagerly loaded collections. However, I understand from this that using hibernate-specific annotations and newer versions of hibernate support this use case.

Can anyone help please? Thanks

Answer 1

This issue has been resolved now.

In a couple of my entities I was using a List for @OneToMany.

Changing to Set resulted in the error going away. Not sure as yet why this worked/was supported in Hibernate 4.3.11 and not 5.2.9. I will update this answer if I find any further information.

Further info with regard to List vs Set can be found here and here.