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。