深入理解spring多数据源配置

2019-11-26 13:18:17

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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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