深入理解spring多数据源配置

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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。