LazyInitializationException: failed to lazily initialize a collection of role could not initialize proxy - no Session

Question

This is asked many times in SO. But they didn't solve my issue so posting again.

Getting following exception while trying to access my application

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.wpt.models.Item.itemCategory, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:575)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:214)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:554)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:142)
    at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:294)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.toForEachIterator(ForEachSupport.java:348)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.supportedTypeForEachIterator(ForEachSupport.java:224)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.prepare(ForEachSupport.java:155)
    at javax.servlet.jsp.jstl.core.LoopTagSupport.doStartTag(LoopTagSupport.java:256)

web.xml

<filter>
        <filter-name>HibernateFilter</filter-name>
        <filter-class>org.springframework.orm.hibernate4.support.OpenSessionInViewFilter</filter-class>
        <init-param>
            <param-name>sessionFactoryBeanName</param-name>
            <param-value>hibernate4AnnotatedSessionFactory</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>HibernateFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

<servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

Spring config:

<tx:annotation-driven transaction-manager="transactionManager"/>
<bean id="transactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager"
    p:sessionFactory-ref="hibernate4AnnotatedSessionFactory">
</bean>

Item.java

@Entity
@Table(name="item")
public class Item {
    @OneToMany(mappedBy="item", fetch=FetchType.LAZY, cascade=CascadeType.ALL)
    private List<ItemCategory> itemCategory = new ArrayList<ItemCategory>();
}

ItemServiceImpl.java

@Override
    @Transactional(readOnly=true)
    public List<Item> getItemsByCategory(int categoryId) {
        return itemDAO.getItemsByCategory(categoryId);
    }

In all of the blogs, it's suggested to either go for EAGER fetch, or use OpenSessionInViewFilter with @Transactional support.

It works will if I use EAGER fetch. But not working the other way. I have implemented all service methods with @Transactional annotation. What mistake I am doing here? Can someone please help?

Answer 1

First of all you have realize what happend if you make an eager fetch. It means the query to the database always bring itemCategory when you request item's. Maybe that is not the behaviour you are expecting.

Second, lazyInitialization exception occurs because you are trying to access to the object itemCategory after close the session. And I suppose the session is closed when you receive the List from the method "getItemsByCategorymethod".

The way I usually resolve this situation (is not making eager fetch) has two ways:

• Pick the itemCategory before close the session. Wherever you call to execute the query, there you should be able to say List listItemCategroy = item.getItemCategory().

• Add a fetch.JOIN to the table itemCategory and it will bring the ItemCategory.

If you want to avoid this error you can add this in your code:

if (Hibernate.isInitilized()){
    ....
}

It will return true if the object is initialized or false if its not.

Answer 2

Okay, after a lot of struggle, I have finally figured out the solution for this issue.

The issue got resolved after I've added contextConfigLocation to DispatcherServlet's <init-param>. After the changes, my DispatcherServlet configuration looks like the following.

<servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value></param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

Reference: This post

Answer 3

The contextConfigLocation is used to indicate where the xml files (eg Spring, spring-security) are located.

Lazy issues doesnt make any sense with Spring configuration to me.

Can you explain it in detail?

Answer 4

use below filter instead of HibernateFilter

<filter>
    <filter-name>OpenSessionInViewFilter</filter-name>
    <filter-class>org.springframework.orm.hibernate4.support.OpenSessionInViewFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>OpenSessionInViewFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

Hope it will help you.