Hibernate 4 - 调用DAO并初始化sessionFactory bean

Question

I'm in the middle of updating my old program to Spring 3.2 and Hibernate 4 and am running into a couple of difficulties with sessionFactory (I was using hibernateTemplate before).

1. I don't think the way I am accessing the DAO is the best way to do it, but I don't see how else to make it work. If I do a simple creation of the DAO object (CSSDAO d = new CSSDAOImpl();), the sessionFactory is always null. If I have it the way I do below, it works. What is the proper way to call the DAO methods? (please ignore the MVC portion of the controller, I know that needs its own work)

2. I'm opening a new session in every method in the DAO. I know this isn't correct, as I should be getting the current session. But everytime I try to get the current session, it says one doesn't exist. How does the session get "initialized" the first time? I thought it would inject it based on the XML configuration, but that doesn't seem to be doing anything here. Any thoughts?

hibernate-cfg.xml

    <?xml version="1.0" encoding="UTF-8"?>


<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">

    <bean id="myDataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="org.apache.derby.jdbc.EmbeddedDriver"></property>
        <property name="url" value="jdbc:derby:C:\Users\Steven\MyDB"></property>
    </bean>

    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="packagesToScan" value="net.form" />
        <property name="dataSource" ref="myDataSource"></property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.DerbyTenSevenDialect
                </prop>
                <prop key="hibernate.show_sql">true</prop>
            </props>
        </property>
        <property name="annotatedClasses">
            <list>
                <value>net.form.StyleChooser</value>
            </list>
        </property>
    </bean>

    <bean id="transactionManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>

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

    <bean id="CSSDAO" class="dao.CSSDAOImpl">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>

</beans>

DAO:

package dao;

import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;

import net.form.StyleChooser;

public class CSSDAOImpl implements CSSDAO {

    private SessionFactory sessionFactory;

    @Autowired
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Transactional
    public List selectAllCSS() {
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        List l = session.createCriteria(StyleChooser.class).list();
        session.flush();
        tx.commit();
        return l;
    }

    @Transactional
    public StyleChooser selectCSSById(Integer ID) {
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        StyleChooser sc = (StyleChooser) session.get(StyleChooser.class, ID);
        session.flush();
        tx.commit();        
        return sc;
    }

    @Transactional
    public Integer insertCSS(StyleChooser insertCSS) {
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        Integer id = (Integer) session.save(insertCSS);
        session.flush();
        tx.commit();
        return id;
    }

    @Transactional
    public void deleteCSS(Integer CSSId) {
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        StyleChooser sc = (StyleChooser) session.get(StyleChooser.class, CSSId);
        session.delete(sc);
        session.flush();
        tx.commit();
    }

    @Transactional
    public void updateCSS(StyleChooser cssWithNewValues) {
        Session session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        session.update(cssWithNewValues);
        session.flush();
        tx.commit();        
    }
}

Accessing DAO...

package net.controllers;

import java.util.List;
import javax.servlet.http.HttpServletRequest;
import net.form.StyleChooser;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.multiaction.MultiActionController;
import dao.CSSDAOImpl;

@Controller
@RequestMapping("/stylechoosertable.html")
public class IndexController extends MultiActionController {

    Resource resource = new FileSystemResource(
            "C:/Users/Steven/Desktop/Programming/workspace/CSSGeneratorHibernate4/WebContent/WEB-INF/hibernate.cfg.xml");
    BeanFactory beanFactory = new XmlBeanFactory(resource);
    CSSDAOImpl dao = (CSSDAOImpl) beanFactory.getBean("CSSDAO");

    @RequestMapping(method = RequestMethod.GET)
    public ModelAndView showIndex(HttpServletRequest request) throws Exception {
        List<StyleChooser> styleChooser = dao.selectAllCSS();
        return new ModelAndView("stylechoosertable", "styleChooser", styleChooser);
    }
}

Answer 1

Few observation:

1. In your retrieve methods, transaction shouldn't be used ie they should be non-transactional.

2. Add <tx:annotation-driven transaction-manager="transactionManager"/> in your configuration to recognize the transactional annotations.

3. If you use @Transactional annotation then don't need to use programmatic transactions. Add the propagation attribute in the @Transactional annotation as @Transactional(propagation=Propagation.REQUIRED) and leave the transaction management to Hibernate.

4. For first time you need to open the session and if not closed you may use the same session next time. For getting the session , better to use an utility method as below:

    private Session getSession(SessionFactory sessionFactory){ Session session = null; try{ session = sessionFactory.getCurrentSession(); }catch(HibernateException hex){ hex.printStackTrace(); } if(session == null && !session.isClosed()){ session = sessionFactory.openSession(); } } 

This way, you will get the session if available and open otherwise open a new session.