spring+Mybatis代码层的读写分离

深藏阁楼爱情的钟 2022-05-18 09:12 160阅读 0赞

原文地址[https://blog.csdn.net/wangpeng047/article/details/8866239][https_blog.csdn.net_wangpeng047_article_details_8866239]

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。

![20130429104020090][]

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。

![20130429105150794][]

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

![20130429111107055][]

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="${dbOne.jdbc.driverClass}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="40"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"jdbcUrl"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${dbOne.jdbc.url}" /> 
       <property name="user" value="${dbOne.jdbc.user}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="42"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"password"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${dbOne.jdbc.password}" /> 
       <property name="initialPoolSize" value="${dbOne.jdbc.initialPoolSize}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="44"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"minPoolSize"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${dbOne.jdbc.minPoolSize}" /> 
       <property name="maxPoolSize" value="${dbOne.jdbc.maxPoolSize}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="46"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"></<span class="hljs-name">bean</span>></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="47"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> </div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="48"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">bean</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"dataSourceTwo"</span> <span class="hljs-attr">class</span>=<span class="hljs-string">"com.mchange.v2.c3p0.ComboPooledDataSource"</span></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="49"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-attr">destroy-method</span>=<span class="hljs-string">"close"</span>></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="50"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"driverClass"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${dbTwo.jdbc.driverClass}" /> 
       <property name="jdbcUrl" value="${dbTwo.jdbc.url}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="52"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"user"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${dbTwo.jdbc.user}" /> 
       <property name="password" value="${dbTwo.jdbc.password}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="54"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"initialPoolSize"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${dbTwo.jdbc.initialPoolSize}" /> 
       <property name="minPoolSize" value="${dbTwo.jdbc.minPoolSize}"</span> /></span></div></div></li><li><div class="hljs-ln-numbers"><div class="hljs-ln-line hljs-ln-n" data-line-number="56"></div></div><div class="hljs-ln-code"><div class="hljs-ln-line"> <span class="hljs-tag"><<span class="hljs-name">property</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"maxPoolSize"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">"${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。

**本篇博文中的拦截器dataSourceAspect配置是有问题的，由于咨询动态多数据源的人比较多，原博主因此做了个demo给大家以供参考，请移步：**

**[Spring动态多数据源实例Demo][Spring_Demo]  
有空把这个错误的更改了，现在先转发**

[https_blog.csdn.net_wangpeng047_article_details_8866239]: https://blog.csdn.net/wangpeng047/article/details/8866239
[20130429104020090]: /images/20220518/bc5d0662ad364625abce5b617f52b1ae.png
[20130429105150794]: /images/20220518/2c483455e82942f9a5162d65ea578f7f.png
[20130429111107055]: /images/20220518/57af99f6a2744db49cacc4703de1becd.png
[Spring_Demo]: http://blog.csdn.net/wangpeng047/article/details/43450189