MyBatis双数据源配置

配置相关

jdbc 配置

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#============================================================================
# MySQL
#============================================================================
jdbc.mysql.driver=com.mysql.jdbc.Driver
jdbc.mysql.url=jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
jdbc.mysql.username=root
jdbc.mysql.password=root

#============================================================================
# MS SQL Server (JTDS)
#============================================================================
jdbc.sqlserver.driver=net.sourceforge.jtds.jdbc.Driver
jdbc.sqlserver.url=jdbc:jtds:sqlserver://127.0.0.1:1433/test
jdbc.sqlserver.username=sa
jdbc.sqlserver.password=sa


#============================================================================
# 通用配置
#============================================================================
jdbc.initialSize=5
jdbc.minIdle=5
jdbc.maxIdle=20
jdbc.maxActive=100
jdbc.maxWait=100000
jdbc.defaultAutoCommit=false
jdbc.removeAbandoned=true
jdbc.removeAbandonedTimeout=600
jdbc.testWhileIdle=true
jdbc.timeBetweenEvictionRunsMillis=60000
jdbc.numTestsPerEvictionRun=20
jdbc.minEvictableIdleTimeMillis=300000

jdbc.properties

单数据源时的Spring配置文件

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<?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:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="classpath:jdbc.properties"/>
</bean>
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${jdbc.mysql.driver}"/>
<property name="url" value="${jdbc.mysql.url}"/>
<property name="username" value="${jdbc.mysql.username}"/>
<property name="password" value="${jdbc.mysql.password}"/>
<property name="initialSize" value="${jdbc.initialSize}"/>
<property name="minIdle" value="${jdbc.minIdle}"/>
<property name="maxIdle" value="${jdbc.maxIdle}"/>
<property name="maxActive" value="${jdbc.maxActive}"/>
<property name="maxWait" value="${jdbc.maxWait}"/>
<property name="defaultAutoCommit" value="${jdbc.defaultAutoCommit}"/>
<property name="removeAbandoned" value="${jdbc.removeAbandoned}"/>
<property name="removeAbandonedTimeout" value="${jdbc.removeAbandonedTimeout}"/>
<property name="testWhileIdle" value="${jdbc.testWhileIdle}"/>
<property name="timeBetweenEvictionRunsMillis" value="${jdbc.timeBetweenEvictionRunsMillis}"/>
<property name="numTestsPerEvictionRun" value="${jdbc.numTestsPerEvictionRun}"/>
<property name="minEvictableIdleTimeMillis" value="${jdbc.minEvictableIdleTimeMillis}"/>
</bean>
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
</bean>

<!-- mybatis.spring自动映射 -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.cnblogs.lzrabbit"/>
</bean>

<!-- 自动扫描,多个包以 逗号分隔 -->
<context:component-scan base-package="com.cnblogs.lzrabbit"/>
<aop:aspectj-autoproxy/>
</beans>

applicationContext.xml

多数据源时Spring配置文件

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<?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:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="classpath:jdbc.properties"/>
</bean>
<bean id="sqlServerDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${jdbc.sqlserver.driver}"/>
<property name="url" value="${jdbc.sqlserver.url}"/>
<property name="username" value="${jdbc.sqlserver.username}"/>
<property name="password" value="${jdbc.sqlserver.password}"/>
<property name="initialSize" value="${jdbc.initialSize}"/>
<property name="minIdle" value="${jdbc.minIdle}"/>
<property name="maxIdle" value="${jdbc.maxIdle}"/>
<property name="maxActive" value="${jdbc.maxActive}"/>
<property name="maxWait" value="${jdbc.maxWait}"/>
<property name="defaultAutoCommit" value="${jdbc.defaultAutoCommit}"/>
<property name="removeAbandoned" value="${jdbc.removeAbandoned}"/>
<property name="removeAbandonedTimeout" value="${jdbc.removeAbandonedTimeout}"/>
<property name="testWhileIdle" value="${jdbc.testWhileIdle}"/>
<property name="timeBetweenEvictionRunsMillis" value="${jdbc.timeBetweenEvictionRunsMillis}"/>
<property name="numTestsPerEvictionRun" value="${jdbc.numTestsPerEvictionRun}"/>
<property name="minEvictableIdleTimeMillis" value="${jdbc.minEvictableIdleTimeMillis}"/>
</bean>
<bean id="mySqlDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${jdbc.mysql.driver}"/>
<property name="url" value="${jdbc.mysql.url}"/>
<property name="username" value="${jdbc.mysql.username}"/>
<property name="password" value="${jdbc.mysql.password}"/>
<property name="initialSize" value="${jdbc.initialSize}"/>
<property name="minIdle" value="${jdbc.minIdle}"/>
<property name="maxIdle" value="${jdbc.maxIdle}"/>
<property name="maxActive" value="${jdbc.maxActive}"/>
<property name="maxWait" value="${jdbc.maxWait}"/>
<property name="defaultAutoCommit" value="${jdbc.defaultAutoCommit}"/>
<property name="removeAbandoned" value="${jdbc.removeAbandoned}"/>
<property name="removeAbandonedTimeout" value="${jdbc.removeAbandonedTimeout}"/>
<property name="testWhileIdle" value="${jdbc.testWhileIdle}"/>
<property name="timeBetweenEvictionRunsMillis" value="${jdbc.timeBetweenEvictionRunsMillis}"/>
<property name="numTestsPerEvictionRun" value="${jdbc.numTestsPerEvictionRun}"/>
<property name="minEvictableIdleTimeMillis" value="${jdbc.minEvictableIdleTimeMillis}"/>
</bean>
<bean id="multipleDataSource" class="com.cnblogs.lzrabbit.MultipleDataSource">
<property name="defaultTargetDataSource" ref="mySqlDataSource"/>
<property name="targetDataSources">
<map>
<entry key="mySqlDataSource" value-ref="mySqlDataSource"/>
<entry key="sqlServerDataSource" value-ref="sqlServerDataSource"/>
</map>
</property>
</bean>
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="multipleDataSource"/>
</bean>

<!-- mybatis.spring自动映射 -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.cnblogs.lzrabbit"/>
</bean>

<!-- 自动扫描,多个包以 逗号分隔 -->
<context:component-scan base-package="com.cnblogs.lzrabbit"/>
<aop:aspectj-autoproxy/>
</beans>

MultipleDataSource实现

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package com.cnblogs.lzrabbit;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

/**
* Created by rabbit on 14-5-25.
*/
public class MultipleDataSource extends AbstractRoutingDataSource {
private static final ThreadLocal<String> dataSourceKey = new InheritableThreadLocal<String>();

public static void setDataSourceKey(String dataSource) {
dataSourceKey.set(dataSource);
}

@Override
protected Object determineCurrentLookupKey() {
return dataSourceKey.get();
}
}

手动数据源切换调用

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package com.cnblogs.lzrabbit;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
* Created by rabbit on 14-5-25.
*/
public class Main {
public static void main(String[] args) {
//初始化ApplicationContext
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");

MySqlMapper mySqlMapper = applicationContext.getBean(MySqlMapper.class);

SqlServerMapper sqlServerMapper = applicationContext.getBean(SqlServerMapper.class);

//设置数据源为MySql,使用了AOP测试时请将下面这行注释
MultipleDataSource.setDataSourceKey("mySqlDataSource");
mySqlMapper.getList();
//设置数据源为SqlServer,使用AOP测试时请将下面这行注释
MultipleDataSource.setDataSourceKey("sqlServerDataSource");
sqlServerMapper.getList();
}
}

MyBatis接口Mapper定义,直接使用注解方式实现

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public interface MySqlMapper {
@Select("select * from MyTable")
List<Map<String,Object>> getList();
}

public interface SqlServerMapper {
@Select("select * from MyTable")
List<Map<String,Object>> getList();
}

使用SpringAOP方式实现自动切换

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package com.cnblogs.lzrabbit;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.stereotype.Component;

@Component
@Aspect
public class MultipleDataSourceAspectAdvice {

@Around("execution(* com.cnblogs.lzrabbit.*.*(..))")
public Object doAround(ProceedingJoinPoint jp) throws Throwable {
if (jp.getTarget() instanceof MySqlMapper) {
MultipleDataSource.setDataSourceKey("mySqlDataSource");
} else if (jp.getTarget() instanceof SqlServerMapper) {
MultipleDataSource.setDataSourceKey("sqlServerDataSource");
}
return jp.proceed();
}
}

配置详解

这里就上面的实现做个简单解释,在我们配置单数据源时可以看到数据源类型使用了org.apache.commons.dbcp.BasicDataSource,而这个代码实现了javax.sql.DataSource接口

配置sqlSessionFactory时org.mybatis.spring.SqlSessionFactoryBean注入参数dataSource类型就是javax.sql.DataSource

实现多数据源的方法就是我们自定义了一个MultipleDataSource,这个类继承自AbstractRoutingDataSource,而AbstractRoutingDataSource继承自AbstractDataSource ,AbstractDataSource 实现了javax.sql.DataSource接口,所以我们的MultipleDataSource也实现了javax.sql.DataSource接口,可以赋值给sqlSessionFactory的dataSource属性

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public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
}

public abstract class AbstractDataSource implements DataSource {
}

再来说下MultipleDataSource的实现原理,MultipleDataSource实现AbstractRoutingDataSource抽象类,然后实现了determineCurrentLookupKey方法,这个方法用于选择具体使用targetDataSources中的哪一个数据源

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<bean id="multipleDataSource" class="com.cnblogs.lzrabbit.MultipleDataSource">
<property name="defaultTargetDataSource" ref="mySqlDataSource"/>
<property name="targetDataSources">
<map>
<entry key="mySqlDataSource" value-ref="mySqlDataSource"/>
<entry key="sqlServerDataSource" value-ref="sqlServerDataSource"/>
</map>
</property>
</bean>

可以看到Spring配置中multipleDataSource设置了两个属性defaultTargetDataSource和targetDataSources,这两个属性定义在AbstractRoutingDataSource,当MyBatis执行查询时会先选择数据源,选择顺序时现根据determineCurrentLookupKey方法返回的值到targetDataSources中去找,若能找到怎返回对应的数据源,若找不到返回默认的数据源defaultTargetDataSource,具体参考AbstractRoutingDataSource的源码

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public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {

private Map<Object, Object> targetDataSources;

private Object defaultTargetDataSource;


/**
* Retrieve the current target DataSource. Determines the
* {@link #determineCurrentLookupKey() current lookup key}, performs
* a lookup in the {@link #setTargetDataSources targetDataSources} map,
* falls back to the specified
* {@link #setDefaultTargetDataSource default target DataSource} if necessary.
* @see #determineCurrentLookupKey()
*/
protected DataSource determineTargetDataSource() {
Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
Object lookupKey = determineCurrentLookupKey();
DataSource dataSource = this.resolvedDataSources.get(lookupKey);
if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
dataSource = this.resolvedDefaultDataSource;
}
if (dataSource == null) {
throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
}
return dataSource;
}

/**
* Determine the current lookup key. This will typically be
* implemented to check a thread-bound transaction context.
* <p>Allows for arbitrary keys. The returned key needs
* to match the stored lookup key type, as resolved by the
* {@link #resolveSpecifiedLookupKey} method.
*/
protected abstract Object determineCurrentLookupKey();
  
  .............

}

在动态切换数据源方法时选择了AOP方式实现,这里实现的简单粗暴,具体应用时根据实际需要灵活变通吧