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Spring3 整合Hibernate3.5 动态切换SessionFactory (切换数据库方言)

一、缘由

上一篇文章Spring3.3 整合 Hibernate3、MyBatis3.2 配置多数据源/动态切换数据源 方法介绍到了怎么样在Sping、MyBatis、Hibernate整合的应用中动态切换DataSource数据源的方法,但最终遗留下一个问题:不能切换数据库方言。数据库方言可能在当前应用的架构中意义不是很大,但是如果单纯用MyBatis或Hibernate做数据库持久化操作,还是要处理这一问题。

 

那么下面将介绍怎么样动态切换SessionFactory,为什么要切换SessionFactory?

因为这里切换SessionFactory就可以实现多数据源和多个SessionFactory,每个SessionFactory有自己独立的数据库配置和SessionFactory的相关配置。我们的数据库方言就配置在SessionFactory这里,所以实现了切换SessionFactory也就实现了切换数据库方言的问题。这个主要是针对Hibernate来操作的,而MyBatis则需要动态切换SqlSessionFactory才行。

 

二、实现代码

1、定义全局切换SessionFactory的工具

package com.hoo.framework.spring.support;
 
/**
 * <b>function:</b> 多数据源
 * @author hoojo
 * @createDate 2013-9-27 上午11:36:57
 * @file CustomerContextHolder.java
 * @package com.hoo.framework.spring.support
 * @project SHMB
 * @blog http://blog.csdn.net/IBM_hoojo
 * @email hoojo_@126.com
 * @version 1.0
 */
public abstract class CustomerContextHolder {
 
    public final static String SESSION_FACTORY_MYSQL = "mysql";
    public final static String SESSION_FACTORY_ORACLE = "oracle";
    
    private static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();  
    
    public static void setCustomerType(String customerType) {  
        contextHolder.set(customerType);  
    }  
      
    public static String getCustomerType() {  
        return contextHolder.get();  
    }  
      
    public static void clearCustomerType() {  
        contextHolder.remove();  
    }  
}

同样上面的静态变量和前一文章中介绍的一致,它需要和下面配置文件中的SessionFactory的key对应。

2、实现自己的SessionFactory

定义好接口

package com.hoo.framework.spring.support.core;
 
import org.hibernate.SessionFactory;
 
/**
 * <b>function:</b> 动态SessionFactory接口
 * @author hoojo
 * @createDate 2013-10-12 下午03:29:52
 * @file DynamicSessionFactory.java
 * @package com.hoo.framework.spring.support.core
 * @project SHMB
 * @blog http://blog.csdn.net/IBM_hoojo
 * @email hoojo_@126.com
 * @version 1.0
 */
public interface DynamicSessionFactory extends SessionFactory {
    
    public SessionFactory getHibernateSessionFactory();
}

 

实现接口

package com.hoo.framework.spring.support.core;
 
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.hibernate.Cache;
import org.hibernate.HibernateException;
import org.hibernate.Interceptor;
import org.hibernate.SessionFactory;
import org.hibernate.StatelessSession;
import org.hibernate.TypeHelper;
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 com.hoo.framework.spring.support.CustomerContextHolder;
 
/**
 * <b>function:</b> 动态数据源实现
 * @author hoojo
 * @createDate 2013-10-12 下午03:31:31
 * @file DynamicSessionFactoryImpl.java
 * @package com.hoo.framework.spring.support.core
 * @project SHMB
 * @blog http://blog.csdn.net/IBM_hoojo
 * @email hoojo_@126.com
 * @version 1.0
 */
@SuppressWarnings({ "unchecked", "deprecation" })
public class DynamicSessionFactoryImpl implements DynamicSessionFactory {
 
    private static final long serialVersionUID = 5384069312247414885L;
    
    private Map<Object, SessionFactory> targetSessionFactorys;  
    private SessionFactory defaultTargetSessionFactory; 
    
    /**
     * @see com.hoo.framework.spring.support.core.DynamicSessionFactory#getHibernateSessionFactory()
     * <b>function:</b> 重写这个方法,这里最关键
     * @author hoojo
     * @createDate 2013-10-18 上午10:45:25
     */
    @Override
    public SessionFactory getHibernateSessionFactory() {
        SessionFactory targetSessionFactory = targetSessionFactorys.get(CustomerContextHolder.getCustomerType());  
        if (targetSessionFactory != null) {  
            return targetSessionFactory;  
        } else if (defaultTargetSessionFactory != null) {  
            return defaultTargetSessionFactory;  
        }  
        return null;
    }
 
 
    @Override
    public void close() throws HibernateException {
        this.getHibernateSessionFactory().close();
    }
 
    @Override
    public boolean containsFetchProfileDefinition(String s) {
        return this.getHibernateSessionFactory().containsFetchProfileDefinition(s);
    }
 
    @Override
    public void evict(Class clazz) throws HibernateException {
        this.getHibernateSessionFactory().evict(clazz);
    }
 
    @Override
    public void evict(Class clazz, Serializable serializable) throws HibernateException {
        this.getHibernateSessionFactory().evict(clazz, serializable);
    }
 
    @Override
    public void evictCollection(String s) throws HibernateException {
        this.getHibernateSessionFactory().evictCollection(s);
    }
 
    @Override
    public void evictCollection(String s, Serializable serializable) throws HibernateException {
        this.getHibernateSessionFactory().evictCollection(s, serializable);
    }
 
    @Override
    public void evictEntity(String entity) throws HibernateException {
        this.getHibernateSessionFactory().evictEntity(entity);
    }
 
    @Override
    public void evictEntity(String entity, Serializable serializable) throws HibernateException {
        this.getHibernateSessionFactory().evictEntity(entity, serializable);
    }
 
    @Override
    public void evictQueries() throws HibernateException {
        this.getHibernateSessionFactory().evictQueries();        
    }
 
    @Override
    public void evictQueries(String queries) throws HibernateException {
        this.getHibernateSessionFactory().evictQueries(queries);        
    }
 
    @Override
    public Map<String, ClassMetadata> getAllClassMetadata() {
        return this.getHibernateSessionFactory().getAllClassMetadata();
    }
 
    @Override
    public Map getAllCollectionMetadata() {
        return this.getHibernateSessionFactory().getAllClassMetadata();
    }
 
    @Override
    public Cache getCache() {
        return this.getHibernateSessionFactory().getCache();
    }
 
    @Override
    public ClassMetadata getClassMetadata(Class clazz) {
        return this.getHibernateSessionFactory().getClassMetadata(clazz);
    }
 
    @Override
    public ClassMetadata getClassMetadata(String classMetadata) {
        return this.getHibernateSessionFactory().getClassMetadata(classMetadata);
    }
 
    @Override
    public CollectionMetadata getCollectionMetadata(String collectionMetadata) {
        return this.getHibernateSessionFactory().getCollectionMetadata(collectionMetadata);
    }
 
    @Override
    public Session getCurrentSession() throws HibernateException {
        return this.getHibernateSessionFactory().getCurrentSession();
    }
 
    @Override
    public Set getDefinedFilterNames() {
        return this.getHibernateSessionFactory().getDefinedFilterNames();
    }
 
    @Override
    public FilterDefinition getFilterDefinition(String definition) throws HibernateException {
        return this.getHibernateSessionFactory().getFilterDefinition(definition);
    }
 
    @Override
    public Statistics getStatistics() {
        return this.getHibernateSessionFactory().getStatistics();
    }
 
    @Override
    public TypeHelper getTypeHelper() {
        return this.getHibernateSessionFactory().getTypeHelper();
    }
 
    @Override
    public boolean isClosed() {
        return this.getHibernateSessionFactory().isClosed();
    }
 
    @Override
    public Session openSession() throws HibernateException {
        return this.getHibernateSessionFactory().openSession();
    }
 
    @Override
    public Session openSession(Interceptor interceptor) throws HibernateException {
        return this.getHibernateSessionFactory().openSession(interceptor);
    }
 
    @Override
    public Session openSession(Connection connection) {
        return this.getHibernateSessionFactory().openSession(connection);
    }
 
    @Override
    public Session openSession(Connection connection, Interceptor interceptor) {
        return this.getHibernateSessionFactory().openSession(connection, interceptor);
    }
 
    @Override
    public StatelessSession openStatelessSession() {
        return this.getHibernateSessionFactory().openStatelessSession();
    }
 
    @Override
    public StatelessSession openStatelessSession(Connection connection) {
        return this.getHibernateSessionFactory().openStatelessSession(connection);
    }
 
    @Override
    public Reference getReference() throws NamingException {
        return this.getHibernateSessionFactory().getReference();
    }
 
    public void setTargetSessionFactorys(Map<Object, SessionFactory> targetSessionFactorys) {
        this.targetSessionFactorys = targetSessionFactorys;
    }
 
    public void setDefaultTargetSessionFactory(SessionFactory defaultTargetSessionFactory) {
        this.defaultTargetSessionFactory = defaultTargetSessionFactory;
    }
 
}

上面最重要的就是getHibernateSessionFactory重写这个方法,其他方法和原来实现的无异。重写这个方法后利用CustomerContextHolder动态设置SessionFactory类型就可以动态的切换SessionFactory。

3、动态的事务管理器,因为我们这里是动态切换SessionFactory,所以事务这块也需要动态切换SessionFactory来完成事务的操作。

package com.hoo.framework.spring.support.tx;
 
import javax.sql.DataSource;
import org.hibernate.SessionFactory;
import org.springframework.orm.hibernate3.HibernateTransactionManager;
import org.springframework.orm.hibernate3.SessionFactoryUtils;
import com.hoo.framework.spring.support.core.DynamicSessionFactory;
 
/**
 * <b>function:</b> 重写HibernateTransactionManager事务管理器,实现自己的动态的事务管理器
 * @author hoojo
 * @createDate 2013-10-12 下午03:54:02
 * @file DynamicTransactionManager.java
 * @package com.hoo.framework.spring.support.tx
 * @project SHMB
 * @blog http://blog.csdn.net/IBM_hoojo
 * @email hoojo_@126.com
 * @version 1.0
 */
public class DynamicTransactionManager extends HibernateTransactionManager {
 
    private static final long serialVersionUID = -4655721479296819154L;
    
    /** 
     * @see org.springframework.orm.hibernate4.HibernateTransactionManager#getDataSource()
     * <b>function:</b> 重写
     * @author hoojo
     * @createDate 2013-10-12 下午03:55:24
     */
    @Override
    public DataSource getDataSource() {
        return SessionFactoryUtils.getDataSource(getSessionFactory());
    }
 
    /** 
     * @see org.springframework.orm.hibernate4.HibernateTransactionManager#getSessionFactory()
     * <b>function:</b> 重写
     * @author hoojo
     * @createDate 2013-10-12 下午03:55:24
     */
    @Override
    public SessionFactory getSessionFactory() {
        DynamicSessionFactory dynamicSessionFactory = (DynamicSessionFactory) super.getSessionFactory();  
        SessionFactory hibernateSessionFactory = dynamicSessionFactory.getHibernateSessionFactory();  
        return hibernateSessionFactory;  
    }
}

这里主要重写getDataSource()/getSessionFactory()这两个方法,getSessionFactory方法是利用我们上面定义的接口来动态获取我们在上下文(CustomerContextHolder)中定义切换的SessionFactory对象。而getDataSource则是获得动态SessionFactory的DataSource,这里也不难理解。

4、至此,重写的接口和实现都完成,下面开始配置相关的代码

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:aop="http://www.springframework.org/schema/aop" 
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
    http://www.springframework.org/schema/beans/spring-beans-3.2.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop-3.2.xsd 
    http://www.springframework.org/schema/tx  
    http://www.springframework.org/schema/tx/spring-tx-3.2.xsd ">
    
    <!-- 配置c3p0数据源 -->
    <bean id="dataSourceOracle" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
        <property name="driverClass" value="${datasource.driver}"/>
        <property name="jdbcUrl" value="${datasource.url}"/>
        <property name="user" value="${datasource.username}"/>
        <property name="password" value="${datasource.password}"/>
                
        <property name="acquireIncrement" value="${c3p0.acquireIncrement}"/>
        <property name="initialPoolSize" value="${c3p0.initialPoolSize}"/>
        <property name="minPoolSize" value="${c3p0.minPoolSize}"/>
        <property name="maxPoolSize" value="${c3p0.maxPoolSize}"/>
        <property name="maxIdleTime" value="${c3p0.maxIdleTime}"/>
        <property name="idleConnectionTestPeriod" value="${c3p0.idleConnectionTestPeriod}"/>
        <property name="maxStatements" value="${c3p0.maxStatements}"/>
        <property name="numHelperThreads" value="${c3p0.numHelperThreads}"/>
        <property name="preferredTestQuery" value="${c3p0.preferredTestQuery}"/>
        <property name="testConnectionOnCheckout" value="${c3p0.testConnectionOnCheckout}"/>
    </bean>
    
    <bean id="dataSourceMySQL" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
        <property name="driverClass" value="com.mysql.jdbc.Driver"/>
        <property name="jdbcUrl" value="jdbc:mysql://172.31.108.178:3306/world?useUnicode=true&amp;characterEncoding=UTF-8&amp;zeroDateTimeBehavior=convertToNull"/>
        <property name="user" value="root"/>
        <property name="password" value="jp2011"/>
                
        <property name="acquireIncrement" value="${c3p0.acquireIncrement}"/>
        <property name="initialPoolSize" value="${c3p0.initialPoolSize}"/>
        <property name="minPoolSize" value="${c3p0.minPoolSize}"/>
        <property name="maxPoolSize" value="${c3p0.maxPoolSize}"/>
        <property name="maxIdleTime" value="${c3p0.maxIdleTime}"/>
        <property name="idleConnectionTestPeriod" value="${c3p0.idleConnectionTestPeriod}"/>
        <property name="maxStatements" value="${c3p0.maxStatements}"/>
        <property name="numHelperThreads" value="${c3p0.numHelperThreads}"/>
        <property name="preferredTestQuery" value="${c3p0.preferredTestQuery}"/>
        <property name="testConnectionOnCheckout" value="${c3p0.testConnectionOnCheckout}"/>
    </bean>
    
    <!-- Annotation 配置sessionFactory,配置数据库连接,注入hibernate数据库配置 -->
    <bean id="mySQLSessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
        <property name="dataSource" ref="dataSourceMySQL"/>
        <property name="packagesToScan" value="com.hoo.**.mysqlentity"/>
        <property name="annotatedClasses">
            <array>
                <value>com.hoo.common.entity.IDGenerator</value>
            </array>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
                <!-- 链接释放策略 on_close | after_transaction | after_statement | auto  -->
                <prop key="hibernate.connection.release_mode">after_transaction</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
            </props>
        </property>
    </bean>
    
    <!-- Annotation 配置sessionFactory,配置数据库连接,注入hibernate数据库配置 -->
    <bean id="oracleSessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
        <property name="dataSource" ref="dataSourceOracle"/>
        <property name="packagesToScan" value="com.hoo.**.entity"/>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.OracleDialect</prop>
                <prop key="hibernate.connection.release_mode">after_transaction</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
                <!--prop key="hibernate.hbm2ddl.auto">update</prop-->
            </props>
        </property>
    </bean>
    
    <!-- 动态SessionFactory -->
    <bean id="sessionFactory" class="com.hoo.framework.spring.support.core.DynamicSessionFactoryImpl">
        <property name="defaultTargetSessionFactory" ref="oracleSessionFactory"/>
        <property name="targetSessionFactorys">
            <map>     
                <entry value-ref="oracleSessionFactory" key="oracle"/>
                <entry value-ref="mySQLSessionFactory" key="mysql"/>
            </map> 
        </property>
    </bean>
 
    <!-- 自定义动态切换SessionFactory事务管理器,注入sessionFactory  -->
    <bean id="transactionManager" class="com.hoo.framework.spring.support.tx.DynamicTransactionManager">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>
    
    <!-- 配置事务的传播特性 -->
    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
            <tx:method name="add*" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
            <tx:method name="edit*" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
            <tx:method name="remove*" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
            <tx:method name="execute*" propagation="REQUIRED" rollback-for="java.lang.Exception"/>
            <tx:method name="*" read-only="true" />
        </tx:attributes>
    </tx:advice>
    
    <!-- 配置那些类、方法纳入到事务的管理 -->
    <aop:config>
        <aop:pointcut expression="execution(* com.hoo.**.service.impl.*.*(..))" id="transactionManagerMethod"/>
        <aop:advisor advice-ref="txAdvice" pointcut-ref="transactionManagerMethod" />
    </aop:config>
</beans>

配置也和我们之前的配置差不多,就是事务管理器部分注入的SessionFactory是我们自己定义的。

5、简单测试

@Test
public void testAdd() {
    // 主要就是这行代码 它才是完成SessionFactory的切换
    CustomerContextHolder.setCustomerType(CustomerContextHolder.SESSION_FACTORY_MYSQL);
    
    DeviceInfo entity = new DeviceInfo();
    entity.setSbbh(System.currentTimeMillis() + "");
    entity.setIpdz("my ip address2");
    entity.setJd(1234);
    try {
        service.add(entity);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

经过测试发现可以查询数据,利用hibernate查询分页也可以生成对应数据库的分页语句。同样在服务层的方法中添加完操作后,特意抛出一个异常,数据也能正常回滚操作,所以DynamicTransactionManager也是起到了该有的作用!

这里我的测试用例是手动切换CustomerContextHolder.setCustomerType的,但实际开发中我们还是得用Spring的Aop中的Interceptor进行切面编程,完成动态切换SessionFactory。上一篇文章Spring3.3 整合 Hibernate3、MyBatis3.2 配置多数据源/动态切换数据源 方法已经提到了(读者可以参考该篇博文中的第二节的3、7小节DataSourceMethodInterceptor MultipleDataSourceInterceptor),这里就不再赘述!

 

三、引发的问题

上述的实现如果在使用不当的情况下,在实际开发中很可能存在一些问题!

问题1是这样的,通常事务是在Service这层完成,这个应该是没有异议。倘若是这样的话,问题便出现了。而通常我们在MVC中的视图层中仅仅会调用Service中一个方法来完成所有当前业务的处理。如果这个Service中同时操作dbA、dbB两个数据库,事务提交的时候是用哪个数据库的事务呢?所以我们把不同数据库的操作放在一个方法,就会出现事务的问题的,除非两个数据库的事务能够同时回滚!

大致情景是:Service中的add4Oracle操作Oracle数据库,Service中的add4MySQL操作MySQL数据库,最后把Service中的add4Oracle、add4MySQL方法放到一个operation方法中,MVC视图层的业务控制调用Service中的operation。像这样的情况,如果add4Oracle或add4MySQL方法中的某一个方法出现异常,就需要把两个数据库事务都回滚。

解决办法就是在Service或Dao中的一个方法中同时操作两个数据库,手动完成事务控制。出现异常就全部回滚,没有异常就全部提交,只能这样牺牲下。

问题2是利用拦截器不能同时切换一个方法操作两个数据库的可能,例如一个service中的query方法即需要用query MySQL,也需要query Oracle。那么解决办法就是在query方法中调用当前service的query4Oracle和query4Oracle,那样绕过去还是能利用拦截器进行动态切换的。

四、总结

要完成数据库方言的切换,我们就需要配置多个SessionFactory利用自己实现的DynamicSessionFactory和CustomerContextHolder完成SessionFactory的切换。利用DynamicTransactionManager完成当前Session的事务操作。通过对这些对象的操作和配置,最终可以完成SessionFactory的动态切换。实际使用中虽然有些问题出现,但是最终还是有解决方案,尽管有些不完美。所谓的完美的东西总有它不完美的地方,这样才算完美,比如断臂的维纳斯女神~!

posted on 2013-10-18 11:58 hoojo 阅读(...) 评论(...) 编辑 收藏