Spring多數據源配置

項目中我們經常會遇到多數據源的問題，尤其是數據同步或定時任務等項目更是如此。多數據源讓人最頭痛的，不是配置多個數據源，而是如何能靈活動態的切換數據源。例如在一個spring和hibernate的框架的項目中，我們在spring配置中往往是配置一個dataSource來連接數據庫，然後綁定給sessionFactory，在dao層代碼中再指定sessionFactory來進行數據庫操作。

正如上圖所示，每一塊都是指定綁死的，如果是多個數據源，也只能是下圖中那種方式。

可看出在Dao層代碼中寫死了兩個SessionFactory，這樣日後如果再多一個數據源，還要改代碼添加一個SessionFactory，顯然這並不符合開閉原則。

那麼正確的做法應該是

代碼如下：

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實體類

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，達到動態更改數據源的目的。當需要增加數據源的時候，我們只需要在applicationContext配置文件中添加aop配置，新建個DataSourceInterceptor即可。而不需要更改任何代碼。

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