Spring多数据源配置

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项目中我们经常会遇到多数据源的问题，尤其是数据同步或定时任务等项目更是如此。多数据源让人最头痛的，不是配置多个数据源，而是如何能灵活动态的切换数据源。例如在一个spring和hibernate的框架的项目中，我们在spring配置中往往是配置一个dataSource来连接数据库，然后绑定给sessionFactory，在dao层代码中再指定sessionFactory来进行数据库操作。

正如上图所示，每一块都是指定绑死的，如果是多个数据源，也只能是下图中那种方式。

可看出在Dao层代码中写死了两个SessionFactory，这样日后如果再多一个数据源，还要改代码添加一个SessionFactory，显然这并不符合开闭原则。

那么正确的做法应该是

代码如下：

1. applicationContext.xml

<?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:cache="http://www.springframework.org/schema/cache"      xmlns:context="http://www.springframework.org/schema/context"      xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee"      xmlns:jms="http://www.springframework.org/schema/jms" xmlns:lang="http://www.springframework.org/schema/lang"      xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:oxm="http://www.springframework.org/schema/oxm"      xmlns:p="http://www.springframework.org/schema/p" xmlns:task="http://www.springframework.org/schema/task"      xmlns:tx="http://www.springframework.org/schema/tx" xmlns:util="http://www.springframework.org/schema/util"      xsi:schemaLocation="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-3.1.xsd        http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache-3.1.xsd        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.1.xsd        http://www.springframework.org/schema/jms http://www.springframework.org/schema/jms/spring-jms-3.1.xsd        http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-3.1.xsd        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd        http://www.springframework.org/schema/oxm http://www.springframework.org/schema/oxm/spring-oxm-3.1.xsd        http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.1.xsd        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd">        <context:annotation-config />        <context:component-scan base-package="com"></context:component-scan>        <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">          <property name="locations">              <list>                  <value>classpath:com/resource/config.properties</value>              </list>          </property>      </bean>        <bean id="dataSourceOne" class="com.mchange.v2.c3p0.ComboPooledDataSource"          destroy-method="close">          <property name="driverClass" value="${dbOne.jdbc.driverClass}" />          <property name="jdbcUrl" value="${dbOne.jdbc.url}" />          <property name="user" value="${dbOne.jdbc.user}" />          <property name="password" value="${dbOne.jdbc.password}" />          <property name="initialPoolSize" value="${dbOne.jdbc.initialPoolSize}" />          <property name="minPoolSize" value="${dbOne.jdbc.minPoolSize}" />          <property name="maxPoolSize" value="${dbOne.jdbc.maxPoolSize}" />      </bean>        <bean id="dataSourceTwo" class="com.mchange.v2.c3p0.ComboPooledDataSource"          destroy-method="close">          <property name="driverClass" value="${dbTwo.jdbc.driverClass}" />          <property name="jdbcUrl" value="${dbTwo.jdbc.url}" />          <property name="user" value="${dbTwo.jdbc.user}" />          <property name="password" value="${dbTwo.jdbc.password}" />          <property name="initialPoolSize" value="${dbTwo.jdbc.initialPoolSize}" />          <property name="minPoolSize" value="${dbTwo.jdbc.minPoolSize}" />          <property name="maxPoolSize" value="${dbTwo.jdbc.maxPoolSize}" />      </bean>        <bean id="dynamicDataSource" class="com.core.DynamicDataSource">          <property name="targetDataSources">              <map key-type="java.lang.String">                  <entry value-ref="dataSourceOne" key="dataSourceOne"></entry>                  <entry value-ref="dataSourceTwo" key="dataSourceTwo"></entry>              </map>          </property>          <property name="defaultTargetDataSource" ref="dataSourceOne">          </property>      </bean>        <bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">          <property name="dataSource" ref="dynamicDataSource" />          <property name="hibernateProperties">              <props>                  <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>                  <prop key="hibernate.current_session_context_class">org.springframework.orm.hibernate4.SpringSessionContext</prop>                  <prop key="hibernate.show_sql">false</prop>                  <prop key="hibernate.format_sql">true</prop>                  <prop key="hbm2ddl.auto">create</prop>              </props>          </property>          <property name="packagesToScan">              <list>                  <value>com.po</value>              </list>          </property>      </bean>        <bean id="transactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager">          <property name="sessionFactory" ref="sessionFactory" />      </bean>        <aop:config>          <aop:pointcut id="transactionPointCut" expression="execution(* com.dao..*.*(..))" />          <aop:advisor advice-ref="txAdvice" pointcut-ref="transactionPointCut" />      </aop:config>        <tx:advice id="txAdvice" transaction-manager="transactionManager">          <tx:attributes>              <tx:method name="add*" propagation="REQUIRED" />              <tx:method name="save*" propagation="REQUIRED" />              <tx:method name="update*" propagation="REQUIRED" />              <tx:method name="delete*" propagation="REQUIRED" />              <tx:method name="*" read-only="true" />          </tx:attributes>      </tx:advice>        <aop:config>          <aop:aspect id="dataSourceAspect" ref="dataSourceInterceptor">              <aop:pointcut id="daoOne" expression="execution(* com.dao.one.*.*(..))" />              <aop:pointcut id="daoTwo" expression="execution(* com.dao.two.*.*(..))" />              <aop:before pointcut-ref="daoOne" method="setdataSourceOne" />              <aop:before pointcut-ref="daoTwo" method="setdataSourceTwo" />          </aop:aspect>      </aop:config>  </beans>

2. DynamicDataSource.class

package com.core;    import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;    public class DynamicDataSource extends AbstractRoutingDataSource{        @Override      protected Object determineCurrentLookupKey() {          return DatabaseContextHolder.getCustomerType();       }    }

3. DatabaseContextHolder.class

package com.core;    public class DatabaseContextHolder {        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();      }  }

4. DataSourceInterceptor.class

package com.core;    import org.aspectj.lang.JoinPoint;  import org.springframework.stereotype.Component;    @Component  public class DataSourceInterceptor {        public void setdataSourceOne(JoinPoint jp) {          DatabaseContextHolder.setCustomerType("dataSourceOne");      }            public void setdataSourceTwo(JoinPoint jp) {          DatabaseContextHolder.setCustomerType("dataSourceTwo");      }  }

5. po实体类

package com.po;    import javax.persistence.Column;  import javax.persistence.Entity;  import javax.persistence.Id;  import javax.persistence.Table;    @Entity  @Table(name = "BTSF_BRAND", schema = "hotel")  public class Brand {        private String id;      private String names;      private String url;        @Id      @Column(name = "ID", unique = true, nullable = false, length = 10)      public String getId() {          return this.id;      }        public void setId(String id) {          this.id = id;      }        @Column(name = "NAMES", nullable = false, length = 50)      public String getNames() {          return this.names;      }        public void setNames(String names) {          this.names = names;      }        @Column(name = "URL", length = 200)      public String getUrl() {          return this.url;      }        public void setUrl(String url) {          this.url = url;      }  }

package com.po;    import javax.persistence.Column;  import javax.persistence.Entity;  import javax.persistence.Id;  import javax.persistence.Table;    @Entity  @Table(name = "CITY", schema = "car")  public class City {        private Integer id;            private String name;        @Id      @Column(name = "ID", unique = true, nullable = false)      public Integer getId() {          return id;      }        public void setId(Integer id) {          this.id = id;      }        @Column(name = "NAMES", nullable = false, length = 50)      public String getName() {          return name;      }        public void setName(String name) {          this.name = name;      }  }

6. BrandDaoImpl.class

package com.dao.one;    import java.util.List;    import javax.annotation.Resource;    import org.hibernate.Query;  import org.hibernate.SessionFactory;  import org.springframework.stereotype.Repository;    import com.po.Brand;    @Repository  public class BrandDaoImpl implements IBrandDao {        @Resource      protected SessionFactory sessionFactory;        @SuppressWarnings("unchecked")      @Override      public List<Brand> findAll() {          String hql = "from Brand";          Query query = sessionFactory.getCurrentSession().createQuery(hql);          return query.list();      }  }

7. CityDaoImpl.class

package com.dao.two;    import java.util.List;    import javax.annotation.Resource;    import org.hibernate.Query;  import org.hibernate.SessionFactory;  import org.springframework.stereotype.Repository;    import com.po.City;    @Repository  public class CityDaoImpl implements ICityDao {        @Resource      private SessionFactory sessionFactory;        @SuppressWarnings("unchecked")      @Override      public List<City> find() {          String hql = "from City";          Query query = sessionFactory.getCurrentSession().createQuery(hql);          return query.list();      }  }

8. DaoTest.class

package com.test;    import java.util.List;    import javax.annotation.Resource;    import org.junit.Test;  import org.junit.runner.RunWith;  import org.springframework.test.context.ContextConfiguration;  import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;  import org.springframework.test.context.transaction.TransactionConfiguration;    import com.dao.one.IBrandDao;  import com.dao.two.ICityDao;  import com.po.Brand;  import com.po.City;    @RunWith(SpringJUnit4ClassRunner.class)  @ContextConfiguration(locations = "classpath:com/resource/applicationContext.xml")  @TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = false)  public class DaoTest {        @Resource      private IBrandDao brandDao;        @Resource      private ICityDao cityDao;        @Test      public void testList() {          List<Brand> brands = brandDao.findAll();          System.out.println(brands.size());            List<City> cities = cityDao.find();          System.out.println(cities.size());      }  }

利用aop，达到动态更改数据源的目的。当需要增加数据源的时候，我们只需要在applicationContext配置文件中添加aop配置，新建个DataSourceInterceptor即可。而不需要更改任何代码。

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