如何使用Spring和Hibernate管理持久性

Question

I just started a web application in Spring using Hibernate and this is the way I figured(after finding few ways of doing it):

GenericDAO

public interface GenericDAO<T extends DomainModel> {
     public T getById(Integer id);
     public List<T> getAll();
     public void saveEntity(T object);
     public void deleteEntity(T object);
}

GenericDAOImpl

public class GenericDAOImpl<T extends DomainModel> implements GenericDAO<T> {

    private Class<T> type;    
    @Autowired
    protected SessionFactory sessionFactory;    
    public void setSessionFactory(SessionFactory sessionFactory){
        this.sessionFactory = sessionFactory;
    }        
    public Session getCurrentSession(){
        return sessionFactory.getCurrentSession();
    }    
    public GenericDAOImpl(Class<T> type) {
        super();
        this.type = type;
    }

    @SuppressWarnings("unchecked")
    @Transactional(readOnly = true)
    @Override
    public T getById(Integer id) {
        if( id == null){
            return null;
        } else {
            return (T) getCurrentSession().get(type, id);
        }        
    }
    @SuppressWarnings("unchecked")
    @Transactional(readOnly = true)
    @Override
    public List<T> getAll() {        
        return getCurrentSession().createQuery("select o from " + type.getName() + " o").list();
    }


    @Transactional(readOnly = true)
    @Override
    public void saveEntity(T object) {
        getCurrentSession().persist(object);        
    }
    @Transactional(readOnly =  true)
    @Override
    public void deleteEntity(T object) {
        getCurrentSession().delete(object);        
    }
}

UserService

public interface UserService {
     public void addUser(User user);
     public List<User> getUsers();
     public User get(Integer id);
     public void delete(User user);
}

UserServiceImpl

@Service
@Transactional
public class UserServiceImpl implements UserService {

    @Autowired
    private GenericDAO<User> userDAO;

    @Override
    public void addUser(User user) {
        userDAO.saveEntity(user);        
    }

    @Override
    public User get(Integer id) {
        return userDAO.getById(id);
    }

    @Override
    public void delete(User user) {
        userDAO.deleteEntity(user);        
    }

    @Override
    public List<User> getUsers() {
       return userDAO.getAll();
    }
}

UserController

@Controller
public class UserController {

     @Autowired
     private UserService userService;

     @RequestMapping(value = "test", method = RequestMethod.GET)
     public String test(){

          User u1 = userService.get(1);        
          return "test";
     }
}

Configuration hibernate

<?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:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:p="http://www.springframework.org/schema/p"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

    <bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/online_auction" />
        <property name="username" value="root" />
        <property name="password" value="123456" />
    </bean>

    <!-- Hibernate 4 SessionFactory Bean definition -->
    <bean id="mySessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="myDataSource" />
        <property name="packagesToScan" value="online_auction.domain_model" />
        <property name="hibernateProperties">
            <props>
                <!-- SQL dialect depends on which database you connect to -->
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
            </props>
        </property>
    </bean>


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

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

Configuration Spring

<?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:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.1.xsd">


    <import resource="classpath:dataSource.xml"/>

    <mvc:annotation-driven />

    <context:component-scan base-package="online_auction"/>

    <mvc:resources location="css" mapping="/css/**" />
    <mvc:resources location="images" mapping="/images/**" />

    <!-- Tiles configuration -->

    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass">
            <value>
                org.springframework.web.servlet.view.tiles2.TilesView
            </value>
        </property>
    </bean>
    <bean id="tilesConfigurer"
        class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
        <property name="definitions">
            <list>
                <value>/WEB-INF/tiles.xml</value>
            </list>
        </property>
    </bean>
    <bean class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor"/>    
</beans>

My questions are:

1. How is the management of the database connection made ? Session per
   web Request ? When is the database connection opened and closed ?
2. Should I create the session in the Service and pass it as parameter to the repositories constructors. Should I also manipulate the session methods like : open session, begin transaction, commit, close session.
3. Since is my first layered application using Repository and Service any suggestions on how to manage database connection/session/transaction are more then welcomed. Thanks in advance!

Answer 1

A pointer for few of your queries - Consider using Spring's OpenSessionInViewInterceptor , it binds Hibernate Session to the thread for the entire processing of the request. You can have it's bean defined as:

<bean name="openSessionInViewInterceptor"
    class="org.springframework.orm.hibernate4.support.OpenSessionInViewInterceptor">
    <property name="sessionFactory">
        <ref bean="sessionFactory" />
    </property>
</bean>

and referred in "interceptors" property of SimpleUrlHandlerMapping bean in Spring's context.xml.

More detail on OpenSessionInViewInterceptor here .