Hibernate SessionFactory becomes null when trying to use it by invoking a method of the same DAO from the Spring MVC controller class

Question

I'm using the Spring version 3.0.2. I want to manage transactions through the @Transactional annotation.

In the applicationContext.xml file, I have the following data source configuration.

<bean id="dataSource"
      class="org.springframework.jdbc.datasource.DriverManagerDataSource"
      p:driverClassName="oracle.jdbc.OracleDriver"
      p:url="jdbc:oracle:thin:@localhost:1521:xe"
      p:username="userName"
      p:password="password"/>

The SessionFactory has been configured as follows.

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
  <property name="dataSource" ref="dataSource" />
  <property name="mappingResources">
  <list>
    <value>hibernate.cfg.xml</value>
  </list>
  </property>
  <property name="hibernateProperties">
    <value>
      hibernate.dialect=org.hibernate.dialect.OracleDialect
    </value>
  </property>
</bean>

The hibernate.cfg.xml file is located in the default package.

---

<bean id="transactionManager"
      class="org.springframework.orm.hibernate3.HibernateTransactionManager"
      p:sessionFactory-ref="sessionFactory" />

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

<bean id="CountryService"
      class="dao.CountryDAO"
      p:sessionFactory-ref="sessionFactory" />

The CountryService interface is simply as follows.

package daoservice;

import java.util.List;
import model.Country;

public interface CountryService
{
    public List<Country>getAllCountries();
}

and the following is its implementation - CountryDAO.

package dao;

import daoservice.CountryService;
import java.util.List;
import model.Country;
import org.hibernate.SessionFactory;
import org.springframework.dao.DataAccessException;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

@Repository
@Transactional(readOnly = true)
final public class CountryDAO implements CountryService
{
    private SessionFactory sessionFactory;

    public void setSessionFactory(SessionFactory sessionFactory)
    {
        this.sessionFactory = sessionFactory;
        System.out.println("template = "+this.sessionFactory);
    }

    @SuppressWarnings("unchecked")
    public List<Country>getAllCountries() throws DataAccessException
    {
        System.out.println("sessionFactory = "+sessionFactory);
        return sessionFactory.getCurrentSession().createQuery("from model.Country order by countryId desc").list();
    }
}

On the deployment time, the following statement,

System.out.println("template = "+this.sessionFactory);

as in the setSessionFactory() method displays something like

template = org.hibernate.impl.SessionFactoryImpl@c63558

This means that the above configurations made in the applicationContext.xml file seem to work.

---

But invoking the method getAllCountries() as in the preceding class from my Spring controller class like (during the GET method)

CountryDAO c=new CountryDAO();
List<Country> countryList = c.getAllCountries();

causes the NullPointerException to be thrown and the statement

System.out.println("sessionFactory = "+sessionFactory);

displays

sessionFactory = null

as obvious.

---

Presumably it appears that a new instance is created by the constructor of CountryDAO and in which the sessionFactory object becomes null.

So how to use the DAO CountryDAO from Spring (or somewhere else)?

---

Tried according to the answer, it threw the following exception.

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'countryController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private dao.CountryDAO controller.CountryController.countryDAO; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [dao.CountryDAO] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

Answer 1

You need to get the CountryDAO bean from the WebApplicationContext or get it injected in your controller by xml or annotations. Something like this:

@Controller
public class SomeController{

    @Autowired
    private CountryService CountryService;

    // Getters and Setters

}

What you are doing with CountryDAO c=new CountryDAO();is just to instanciate a new object that is not managed by the spring container, so of course it will have its session factory set to null.