适用范围：适合SSH架构访问多个数据库，数据库的类型和表结构不必相同，且没有跨库事务的情况（跨库事务最好用分布式事务处理）。
实现方式：我们可以在spring的配置文件中配置多个sessionFactory,如：<bean id="aDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName"> <value>${adriver}</value> </property> <property name="url"> <value>${aurl}</value> </property> <property name="username"> <value>${ausername}</value> </property> <property name="password"> <value>${apassword}</value> </property></bean><bean id="bDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName"> <value>${bdriver}</value> </property> <property name="url"> <value>${burl}</value> </property> <property name="username"> <value>${busername}</value> </property> <property name="password"> <value>${bpassword}</value> </property></bean><bean id="cDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName"> <value>${cdriver}</value> </property> <property name="url"> <value>${curl}</value> </property> <property name="username"> <value>${cusername}</value> </property> <property name="password"> <value>${cpassword}</value> </property></bean>
<!-- Hibernate SessionFactorys --><bean id="aSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"> <ref local="aDataSource" /> </property> <property name="mappingResources"> <list> <value> .hbm.xml文件 </value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect"> ${ahibernate.dialect} </prop> <prop key="hibernate.show_sql">true</prop> <prop key="format_sql">true</prop> </props> </property></bean><bean id="bSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"> <ref local="bDataSource" /> </property> <property name="mappingResources"> <list> <value> .hbm.xml文件 </value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect"> ${bhibernate.dialect} </prop> <prop key="hibernate.show_sql">true</prop> <prop key="format_sql">true</prop> </props> </property></bean><bean id="cSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"> <ref local="cDataSource" /> </property> <property name="mappingResources"> <list> <value> .hbm.xml文件 </value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect"> ${chibernate.dialect} </prop> <prop key="hibernate.show_sql">true</prop> <prop key="format_sql">true</prop> </props> </property></bean><bean id="sessionFactory" class="com.cintel.dcp.datasource.MultiSessionFactory"> <property name="sessionFactory"><ref local="aSessionFactory"/></property></bean>注意：最后一个com.cintel.dcp.datasource.MultiSessionFactory要自己实现，它实现了SessionFactory接口和ApplicationContext接口，如下：package com.cintel.dcp.datasource;
import java.io.Serializable;import java.sql.Connection;import java.util.Map;import java.util.Set;
import javax.naming.NamingException;import javax.naming.Reference;
import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.hibernate.HibernateException;import org.hibernate.Interceptor;import org.hibernate.SessionFactory;import org.hibernate.StatelessSession;import org.hibernate.classic.Session;import org.hibernate.engine.FilterDefinition;import org.hibernate.metadata.ClassMetadata;import org.hibernate.metadata.CollectionMetadata;import org.hibernate.stat.Statistics;import org.springframework.beans.factory.NoSuchBeanDefinitionException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;public class MultiSessionFactory implements SessionFactory, ApplicationContextAware {private static final long serialVersionUID = 2064557324203496378L;private static final Log log = LogFactory.getLog(MultiSessionFactory.class);private ApplicationContext applicationContext = null;private SessionFactory sessionFactory = null;public ApplicationContext getApplicationContext() { return applicationContext;}public void setApplicationContext(ApplicationContext applicationContext) { this.applicationContext = applicationContext;}public SessionFactory getSessionFactory(String sessionFactoryName) { log.debug("sessionFactoryName:"+sessionFactoryName); try{ if(sessionFactoryName==null||sessionFactoryName.equals("")){ return sessionFactory; } return (SessionFactory)this.getApplicationContext().getBean(sessionFactoryName); }catch(NoSuchBeanDefinitionException ex){ throw new RuntimeException("There is not the sessionFactory <name:"+sessionFactoryName+"> in the applicationContext!"); }}public SessionFactory getSessionFactory() { String sessionFactoryName = CustomerContextHolder.getCustomerType(); return getSessionFactory(sessionFactoryName);}public void setSessionFactory(SessionFactory sessionFactory) { this.sessionFactory = sessionFactory;}/* (non-Javadoc)* @see org.hibernate.SessionFactory#close()*/public void close() throws HibernateException { getSessionFactory().close();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evict(java.lang.Class)*/public void evict(Class persistentClass) throws HibernateException { getSessionFactory().evict(persistentClass);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evict(java.lang.Class, java.io.Serializable)*/public void evict(Class persistentClass, Serializable id) throws HibernateException { getSessionFactory().evict(persistentClass, id);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evictCollection(java.lang.String)*/public void evictCollection(String roleName) throws HibernateException { getSessionFactory().evictCollection(roleName);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evictCollection(java.lang.String, java.io.Serializable)*/public void evictCollection(String roleName, Serializable id) throws HibernateException { getSessionFactory().evictCollection(roleName, id);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evictEntity(java.lang.String)*/public void evictEntity(String entityName) throws HibernateException { getSessionFactory().evictEntity(entityName);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evictEntity(java.lang.String, java.io.Serializable)*/public void evictEntity(String entityName, Serializable id) throws HibernateException { getSessionFactory().evictEntity(entityName, id);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evictQueries()*/public void evictQueries() throws HibernateException { getSessionFactory().evictQueries();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#evictQueries(java.lang.String)*/public void evictQueries(String cacheRegion) throws HibernateException { getSessionFactory().evictQueries(cacheRegion);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getAllClassMetadata()*/public Map getAllClassMetadata() throws HibernateException { return getSessionFactory().getAllClassMetadata();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getAllCollectionMetadata()*/public Map getAllCollectionMetadata() throws HibernateException { return getSessionFactory().getAllCollectionMetadata();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getClassMetadata(java.lang.Class)*/public ClassMetadata getClassMetadata(Class persistentClass) throws HibernateException { return getSessionFactory().getClassMetadata(persistentClass);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getClassMetadata(java.lang.String)*/public ClassMetadata getClassMetadata(String entityName) throws HibernateException { return getSessionFactory().getClassMetadata(entityName);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getCollectionMetadata(java.lang.String)*/public CollectionMetadata getCollectionMetadata(String roleName) throws HibernateException { return getSessionFactory().getCollectionMetadata(roleName);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getCurrentSession()*/public Session getCurrentSession() throws HibernateException { return getSessionFactory().getCurrentSession();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getDefinedFilterNames()*/public Set getDefinedFilterNames() { return getSessionFactory().getDefinedFilterNames();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getFilterDefinition(java.lang.String)*/public FilterDefinition getFilterDefinition(String filterName) throws HibernateException { return getSessionFactory().getFilterDefinition(filterName);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#getStatistics()*/public Statistics getStatistics() { return getSessionFactory().getStatistics();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#isClosed()*/public boolean isClosed() { return getSessionFactory().isClosed();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#openSession()*/public Session openSession() throws HibernateException { return getSessionFactory().openSession();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#openSession(java.sql.Connection)*/public Session openSession(Connection connection) { return getSessionFactory().openSession(connection);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#openSession(org.hibernate.Interceptor)*/public Session openSession(Interceptor interceptor) throws HibernateException { return getSessionFactory().openSession(interceptor);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#openSession(java.sql.Connection, org.hibernate.Interceptor)*/public Session openSession(Connection connection, Interceptor interceptor) { return getSessionFactory().openSession(connection, interceptor);}/* (non-Javadoc)* @see org.hibernate.SessionFactory#openStatelessSession()*/public StatelessSession openStatelessSession() { return getSessionFactory().openStatelessSession();}/* (non-Javadoc)* @see org.hibernate.SessionFactory#openStatelessSession(java.sql.Connection)*/public StatelessSession openStatelessSession(Connection connection) { return getSessionFactory().openStatelessSession(connection);}/* (non-Javadoc)* @see javax.naming.Referenceable#getReference()*/public Reference getReference() throws NamingException { return getSessionFactory().getReference();}}
然后我用一个常量类来标识sessionFactorypublic class DynamicDataSourceType {public static final String A= "aSessionFactory";public static final String B= "bSessionFactory";public static final String C= "cSessionFactory";}
最后一个关键类：用来存放当前正在使用的sessionFactorypublic class CustomerContextHolder {
private static final ThreadLocal contextHolder = new ThreadLocal();
public static void setCustomerType(String customerType) { Assert.notNull(customerType, "customerType cannot be null"); contextHolder.set(customerType);}
public static String getCustomerType() { return (String) contextHolder.get();}
public static void clearCustomerType() { contextHolder.remove();}}
可以在action、service、dao中进行数据库切换，切换方式：CustomerContextHolder.setCustomerType(DynamicDataSourceType.A);
