向ServletContextListener注入依赖项

Question

I'm developing a web application and I'm new to Spring Hibernate. In there I have a ServletContextListener to run a method periodically. In that class I'm calling a method in my ReceiptDao class.

Below is ServletContextListener class

public class MailReminder implements ServletContextListener {

    public void contextInitialized(ServletContextEvent arg0) {
    ServletContext servletContext = arg0.getServletContext();
    System.out.println("ServletContextListener started");

    int delay = 1000;
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new TimerTask(){
    public void run(){

        ReceiptDao receiptDao=new ReceiptDao();
        receiptDao.listReceipts();
        }
    },delay, 1000*60);
    }


    public void contextDestroyed(ServletContextEvent arg0) {

    ServletContext servletContext = arg0.getServletContext();
    Timer timer = (Timer)servletContext.getAttribute ("timer");
    if (timer != null)
    timer.cancel();
    servletContext.removeAttribute ("timer");
    System.out.println("ServletContextListener destroyed");
    }
    }

Below is the method in ReceiptDao

 @Autowired
 private SessionFactory sessionFactory;

 @SuppressWarnings("unchecked")
 public List<Receipt> listReceipts() {

    Session session = sessionFactory.openSession();  //line 150
    Criteria crit= session.createCriteria(Receipt.class);
    crit.add(Restrictions.eq("ReceiptId",2 ));
    List<Receipt> receiptlist= crit.list();
    session.close();
    return receiptlist;

    }

It gives a NullPointerException in line 150. I know it happens because I'm calling this method through Spring nonmanaged class. But I have no idea about how to inject my Spring managed ReceiptDao into my ServletContextListener.

Could you please tell me how to inject it. Please mention the changes I have to do in my web.xml and spring-config-file.xml too.

Answer 1

To create a new class and to inject other class, you need to create beans.

In you case to inject your receiptDAO; you need to to as following:

 <beans>
     <bean id="receiptDAO" class="{path}.ReceiptDao" singleton="true"/>

     <bean id="mailReminder" class="{path}.MailReminder" scope="singleton">
       <property name="receiptDAO">
         <ref bean="receiptDAO"/>
      </property>         
    </bean>
  </beans>

In your class just create:

private ReceiptDao receiptDAO;
public getReceiptDAO()
{
  return receiptDAO;
}

And you can use it freely