How to fix LazyInitializationException

I wanted to show the number of items in a certain category and what I get is a LazyInitializationException (failed to lazily initialize a collection of role – no session or session was closed). It seems that because the fetch mode for the collection items is lazy, the session is not available anymore when I actually need it.

The solution is to add an interceptor to the UrlHandlerMapping in the dispatcher servlet like so:

<bean id="urlMapping"
  class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="interceptors">
      <list>
        <ref bean="openSessionInViewInterceptor" />
     </list>
    </property>

   <!-- ... -->

</bean>

That interceptor is a OpenSessionInViewInterceptor which will make the session available in the view layer.

<bean name="openSessionInViewInterceptor"
  class="org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor">
    <property name="sessionFactory">
      <ref bean="sessionFactory" />
    </property>
</bean>