SessionFactory在Hibernate中的作用

1 .先来说一下Configuration的作用

Configuration的构造方法: 将Hibernate的配置信息(hibernate.cfg.xml)读入到内存.

2.SessionFactory的作用

把Configuration对象中的所有配置信息拷贝到SessionFactory的缓存中,创建后不再与Configuration对象关联.

Hibernate的配置信息举例:

hibernate.cfg.xml:<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration>    <session-factory>        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>        <property name="hibernate.connection.password">root</property>        <property name="hibernate.connection.url">jdbc:mysql:///crm</property>        <property name="hibernate.connection.username">root</property>        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>    </session-factory></hibernate-configuration>

3.注入问题

dataSource数据源是注入给sessionFactory的,然后关联到session中.
sessionFactory需要注入给DAO, 做项目时,经常是让DAO层继承HibernateDaoSupport. 因为HibernareDaoSupport有个属性就是sessionFactory, 所以向DAO类中注入sessionFactory时,就是向hibernateDaoSupport中注入了.

eg:
DAO类:

public class ItemsDaoImpl extends HibernateDaoSupport implements ItemsDao {    @Override    public List<Items> findAll() {        // TODO Auto-generated method stub        return (List<Items>) this.getHibernateTemplate().find("from Items");    }    @Override    public Items findById(Integer id) {        // TODO Auto-generated method stub        return getHibernateTemplate().get(Items.class, id);    }    @Override    public void update(Items item) {        // TODO Auto-generated method stub        getHibernateTemplate().update(item);    }}

applicationContext.xml(下面例子是spring和hernate的配置文件整合成一个的演示)

    <!-- spring相关配置 -->    <!-- 1. 加载jdbc.prpperties -->    <context:property-placeholder location="classpath:jdbc.properties"/>    <!-- 2.数据源 -->    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">        <property name="driverClass" value="${jdbc.driverClass}"></property>        <property name="jdbcUrl" value="${jdbc.url}"></property>        <property name="user" value="${jdbc.username}"></property>        <property name="password" value="${jdbc.password}"></property>    </bean>    <!-- 3.SessionFactory -->    <bean id="sessionFactory" class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">        <property name="dataSource" ref="dataSource"></property>        <property name="hibernateProperties">            <props>                <prop key="hibernate.show_sql">true</prop>                <prop key="hibernate.format_sql">true</prop>                <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>            </props>        </property>        <property name="mappingLocations" value="classpath:com/qx/domain/*.hbm.xml"></property>    </bean>    <!-- 4. 平台事务管理器 -->    <bean id="txManager" class="org.springframework.orm.hibernate5.HibernateTransactionManager">        <property name="sessionFactory" ref="sessionFactory"></property>        <property name="dataSource" ref="dataSource"></property>    </bean>