原文来自:http://www.sjsjw.com/kf_web/article/13_31666_9704.asp
1.问题的引入
对于普通的SSH框架而言,一般配置一个数据源,一个SessionFactory,一个事务管理和对应的ProxyCreate。那么当项目需要操作多个数据库时,如何配置呢?
方案1
配置2个数据源,2个对应的SessionFactory,2个事务等。Spring的配置如下:
<?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:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <!-- 引入datasource配置文件 --> <context:property-placeholder location="classpath:datasource.properties" /> <!--创建mysql jdbc数据源 --> <bean id="mysqlDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="driverClass" value="${jdbc.mysql.driver}" /> <property name="jdbcUrl" value="${jdbc.mysql.url}" /> <property name="user" value="${jdbc.mysql.username}" /> <property name="password" value="${jdbc.mysql.password}" /> <!-- 指定连接数据库连接池的最小连接数 --> <property name="minPoolSize" value="10" /> <!-- 指定连接数据库连接池的最大连接数 --> <property name="maxPoolSize" value="30" /> <!-- 指定连接数据库连接池的连接的最大空闲时间 --> <property name="maxIdleTime" value="1800" /> <property name="acquireIncrement" value="2" /> <property name="maxStatements" value="0" /> <!-- 指定连接数据库连接池的初始化连接数 --> <property name="initialPoolSize" value="2" /> <property name="idleConnectionTestPeriod" value="1800" /> <!-- 当连接失败时,尝试重新连接的次数 --> <property name="acquireRetryAttempts" value="30" /> <property name="breakAfterAcquireFailure" value="true" /> <property name="testConnectionOnCheckout" value="false" /> </bean> <!--创建oracle jdbc数据源 --> <bean id="oracleDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="driverClass" value="${jdbc.oracle.driver}" /> <property name="jdbcUrl" value="${jdbc.oracle.url}" /> <property name="user" value="${jdbc.oracle.username}" /> <property name="password" value="${jdbc.oracle.password}" /> <!-- 指定连接数据库连接池的最小连接数 --> <property name="minPoolSize" value="10" /> <!-- 指定连接数据库连接池的最大连接数 --> <property name="maxPoolSize" value="30" /> <!-- 指定连接数据库连接池的连接的最大空闲时间 --> <property name="maxIdleTime" value="1800" /> <property name="acquireIncrement" value="2" /> <property name="maxStatements" value="0" /> <!-- 指定连接数据库连接池的初始化连接数 --> <property name="initialPoolSize" value="2" /> <property name="idleConnectionTestPeriod" value="1800" /> <!-- 当连接失败时,尝试重新连接的次数 --> <property name="acquireRetryAttempts" value="1" /> <property name="breakAfterAcquireFailure" value="true" /> <property name="testConnectionOnCheckout" value="false" /> </bean> <!-- 创建MysqlSessionFactory--> <bean id="mysqlSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> <property name="dataSource" ref="mysqlDataSource" /> <property name="hibernateProperties"> <props> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop> <prop key="current_session_context_class">thread</prop> </props> </property> <property name="mappingResources"> <list> <value>edu/njupt/zhb/model/mysql/Student.hbm.xml</value> </list> </property> </bean> <!-- 创建OracleSessionFactory--> <bean id="oracleSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> <property name="dataSource" ref="oracleDataSource" /> <property name="hibernateProperties"> <props> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.dialect">org.hibernate.dialect.OracleDialect</prop> <prop key="current_session_context_class">thread</prop> </props> </property> <property name="mappingResources"> <list> <value>edu/njupt/zhb/model/oracle/Student.hbm.xml</value> </list> </property> </bean> <!-- 配置Mysql事务 --> <bean id="mysqlTransactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager"> <property name="sessionFactory"> <ref local="mysqlSessionFactory" /> </property> </bean> <!--Mysql hibernate4必须配置为开启事务 否则 getCurrentSession()获取不到--> <bean id="mysqlTransactionInterceptor" class="org.springframework.transaction.interceptor.TransactionInterceptor"> <property name="transactionManager"> <ref local="mysqlTransactionManager" /> </property> <property name="transactionAttributes"> <props> <prop key="register">PROPAGATION_REQUIRED</prop> <prop key="get*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="find*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="select*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="query*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="sync*">PROPAGATION_REQUIRED</prop> <prop key="finish*">PROPAGATION_REQUIRED</prop> <prop key="add*">PROPAGATION_REQUIRED</prop> <prop key="insert*">PROPAGATION_REQUIRED</prop> <prop key="edit*">PROPAGATION_REQUIRED</prop> <prop key="update*">PROPAGATION_REQUIRED</prop> <prop key="save*">PROPAGATION_REQUIRED</prop> <prop key="remove*">PROPAGATION_REQUIRED</prop> <prop key="delete*">PROPAGATION_REQUIRED</prop> <prop key="modify*">PROPAGATION_REQUIRED</prop> <prop key="*">PROPAGATION_REQUIRED,-java.lang.Exception</prop> </props> </property> </bean> <!-- 配置oracle事务 --> <bean id="oracleTransactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager"> <property name="sessionFactory"> <ref local="oracleSessionFactory" /> </property> </bean> <!--Mysql hibernate4必须配置为开启事务 否则 getCurrentSession()获取不到--> <bean id="oracleTransactionInterceptor" class="org.springframework.transaction.interceptor.TransactionInterceptor"> <property name="transactionManager"> <ref local="oracleTransactionManager" /> </property> <property name="transactionAttributes"> <props> <prop key="register">PROPAGATION_REQUIRED</prop> <prop key="get*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="find*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="select*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="query*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="sync*">PROPAGATION_REQUIRED</prop> <prop key="finish*">PROPAGATION_REQUIRED</prop> <prop key="add*">PROPAGATION_REQUIRED</prop> <prop key="insert*">PROPAGATION_REQUIRED</prop> <prop key="edit*">PROPAGATION_REQUIRED</prop> <prop key="update*">PROPAGATION_REQUIRED</prop> <prop key="save*">PROPAGATION_REQUIRED</prop> <prop key="remove*">PROPAGATION_REQUIRED</prop> <prop key="delete*">PROPAGATION_REQUIRED</prop> <prop key="modify*">PROPAGATION_REQUIRED</prop> <prop key="*">PROPAGATION_REQUIRED,-java.lang.Exception</prop> </props> </property> </bean> <!-- autoproxy 自动创建代理--> <bean id="ProxyCreator" class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator"> <property name="beanNames"> <list> <value>*ServiceImpl</value> </list> </property> <property name="interceptorNames"> <list> <value>mysqlTransactionInterceptor</value> <value>oracleTransactionInterceptor</value> </list> </property> </bean> <!--********************************注入Mysql Dao*********************************************--> <bean id="mysqlBaseDao" class="edu.njupt.zhb.dao.MysqlBaseDao"> <property name="sessionFactory" ref="mysqlSessionFactory"></property> </bean> <!--********************************注入Oracle Dao*********************************************--> <bean id="oracleBaseDao" class="edu.njupt.zhb.dao.OracleBaseDao"> <property name="sessionFactory" ref="oracleSessionFactory"></property> </bean> <!--********************************注入Services********************************--> <!--********************************注入Action********************************--> </beans>
优缺点分析:
优点:我们能够在程序中正常得使用2个不同的Dao,而且可以调用dao的getSessionFactory().getCurrentSession(),使用起来特别的方便。每个Dao都有自己的事务管理,安全性各方面和一个数据库一样。
缺点:由于事务的配置和自动创建代理的配置,只要有一个数据库连接不了,即便两外一个数据库可以连接,整个项目仍然无法正常启动。对于一些特殊的应用场景,该方案有着很大的缺陷。
比如某项目的需求为:一个项目需要同时操作2个数据库,如果一个数据库无法连接,那么项目就操作另外一个数据库,同时,将操作的动作记录下来,等另外一个数据库可以连接的时候,再将之前的操作同步到这个数据库中。而且要求,当项目启动的时候,即便只有一个数据库可以连接,那么项目仍然要正常运行。
方案2
为了解决上述的需求,我们将其中一个数据库作为本地数据库,另外一个作为远程数据库,当远程数据库无法连接时,我们跳过。整个项目使用本地数据库即可,同时将需要同步的数据,保存起来,待可连接时,再同步。
<?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:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <!-- 引入datasource配置文件 --> <context:property-placeholder location="classpath:datasource.properties" /> <!--创建mysql jdbc数据源 --> <bean id="mysqlDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="driverClass" value="${jdbc.mysql.driver}" /> <property name="jdbcUrl" value="${jdbc.mysql.url}" /> <property name="user" value="${jdbc.mysql.username}" /> <property name="password" value="${jdbc.mysql.password}" /> <!-- 指定连接数据库连接池的最小连接数 --> <property name="minPoolSize" value="10" /> <!-- 指定连接数据库连接池的最大连接数 --> <property name="maxPoolSize" value="30" /> <!-- 指定连接数据库连接池的连接的最大空闲时间 --> <property name="maxIdleTime" value="1800" /> <property name="acquireIncrement" value="2" /> <property name="maxStatements" value="0" /> <!-- 指定连接数据库连接池的初始化连接数 --> <property name="initialPoolSize" value="2" /> <property name="idleConnectionTestPeriod" value="1800" /> <!-- 当连接失败时,尝试重新连接的次数 --> <property name="acquireRetryAttempts" value="30" /> <property name="breakAfterAcquireFailure" value="true" /> <property name="testConnectionOnCheckout" value="false" /> </bean> <!--创建oracle jdbc数据源 --> <bean id="oracleDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="driverClass" value="${jdbc.oracle.driver}" /> <property name="jdbcUrl" value="${jdbc.oracle.url}" /> <property name="user" value="${jdbc.oracle.username}" /> <property name="password" value="${jdbc.oracle.password}" /> <!-- 指定连接数据库连接池的最小连接数 --> <property name="minPoolSize" value="10" /> <!-- 指定连接数据库连接池的最大连接数 --> <property name="maxPoolSize" value="30" /> <!-- 指定连接数据库连接池的连接的最大空闲时间 --> <property name="maxIdleTime" value="1800" /> <property name="acquireIncrement" value="2" /> <property name="maxStatements" value="0" /> <!-- 指定连接数据库连接池的初始化连接数 --> <property name="initialPoolSize" value="2" /> <property name="idleConnectionTestPeriod" value="1800" /> <!-- 当连接失败时,尝试重新连接的次数 --> <property name="acquireRetryAttempts" value="1" /> <property name="breakAfterAcquireFailure" value="true" /> <property name="testConnectionOnCheckout" value="false" /> </bean> <!-- 创建MysqlSessionFactory--> <bean id="mysqlSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> <property name="dataSource" ref="mysqlDataSource" /> <property name="hibernateProperties"> <props> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop> <prop key="current_session_context_class">thread</prop> </props> </property> <property name="mappingResources"> <list> <value>edu/njupt/zhb/model/mysql/Student.hbm.xml</value> </list> </property> </bean> <!-- 创建OracleSessionFactory--> <bean id="oracleSessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"> <property name="dataSource" ref="oracleDataSource" /> <property name="hibernateProperties"> <props> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.dialect">org.hibernate.dialect.OracleDialect</prop> <prop key="current_session_context_class">thread</prop> </props> </property> <property name="mappingResources"> <list> <value>edu/njupt/zhb/model/oracle/Student.hbm.xml</value> </list> </property> </bean> <!-- 配置Mysql事务 --> <bean id="mysqlTransactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager"> <property name="sessionFactory"> <ref local="mysqlSessionFactory" /> </property> </bean> <!--Mysql hibernate4必须配置为开启事务 否则 getCurrentSession()获取不到--> <bean id="mysqlTransactionInterceptor" class="org.springframework.transaction.interceptor.TransactionInterceptor"> <property name="transactionManager"> <ref local="mysqlTransactionManager" /> </property> <property name="transactionAttributes"> <props> <prop key="register">PROPAGATION_REQUIRED</prop> <prop key="get*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="find*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="select*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="query*">PROPAGATION_REQUIRED,readOnly</prop> <prop key="sync*">PROPAGATION_REQUIRED</prop> <prop key="finish*">PROPAGATION_REQUIRED</prop> <prop key="add*">PROPAGATION_REQUIRED</prop> <prop key="insert*">PROPAGATION_REQUIRED</prop> <prop key="edit*">PROPAGATION_REQUIRED</prop> <prop key="update*">PROPAGATION_REQUIRED</prop> <prop key="save*">PROPAGATION_REQUIRED</prop> <prop key="remove*">PROPAGATION_REQUIRED</prop> <prop key="delete*">PROPAGATION_REQUIRED</prop> <prop key="modify*">PROPAGATION_REQUIRED</prop> <prop key="*">PROPAGATION_REQUIRED,-java.lang.Exception</prop> </props> </property> </bean> <!-- autoproxy 自动创建代理--> <bean id="ProxyCreator" class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator"> <property name="beanNames"> <list> <value>*ServiceImpl</value> </list> </property> <property name="interceptorNames"> <list> <value>mysqlTransactionInterceptor</value> </list> </property> </bean> <!--********************************注入Mysql Dao*********************************************--> <bean id="mysqlBaseDao" class="edu.njupt.zhb.dao.MysqlBaseDao"> <property name="sessionFactory" ref="mysqlSessionFactory"></property> </bean> <!--********************************注入Oracle Dao*********************************************--> <bean id="oracleBaseDao" class="edu.njupt.zhb.dao.OracleBaseDao"> <property name="sessionFactory" ref="oracleSessionFactory"></property> </bean> <!--********************************注入Services********************************--> <!--********************************注入Action********************************--> </beans>
这种配置下,oracleBaseDao的数据源的属性:acquireRetryAttempts的值配置为1,即便无法连接,我们也只需要连接一次,不会出现“卡住”的情况。而且,由于oracleBaseDao中,我们没有配置事务,因此,dao无法获得getCurrentSession,只能通过sessionFactory().openSession()来使用Hibernate。同时为了捕获异常,我们将session设置成手动提交的方式。