MyBatis雙數據源配置

配置相關

jdbc 配置

#============================================================================
# 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

單數據源時的Spring配置文件

<?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自動映射 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.cnblogs.lzrabbit"/>
    </bean>

    <!-- 自動掃描，多個包以 逗號分隔 -->
    <context:component-scan base-package="com.cnblogs.lzrabbit"/>
    <aop:aspectj-autoproxy/>
</beans>

applicationContext.xml

多數據源時Spring配置文件

<?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自動映射 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.cnblogs.lzrabbit"/>
    </bean>

    <!-- 自動掃描，多個包以 逗號分隔 -->
    <context:component-scan base-package="com.cnblogs.lzrabbit"/>
    <aop:aspectj-autoproxy/>
</beans>

MultipleDataSource實現

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();
    }
}

手動數據源切換調用

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);
        
        //設置數據源為MySql,使用了AOP測試時請將下面這行注釋
        MultipleDataSource.setDataSourceKey("mySqlDataSource");
        mySqlMapper.getList();
        //設置數據源為SqlServer,使用AOP測試時請將下面這行注釋
        MultipleDataSource.setDataSourceKey("sqlServerDataSource");
        sqlServerMapper.getList();
    }
}

MyBatis接口Mapper定義，直接使用注解方式實現

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方式實現自動切換

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();
    }
}

---

配置詳解

這里就上面的實現做個簡單解釋，在我們配置單數據源時可以看到數據源類型使用了org.apache.commons.dbcp.BasicDataSource，而這個代碼實現了javax.sql.DataSource接口

配置sqlSessionFactory時org.mybatis.spring.SqlSessionFactoryBean注入參數dataSource類型就是javax.sql.DataSource

實現多數據源的方法就是我們自定義了一個MultipleDataSource，這個類繼承自AbstractRoutingDataSource，而AbstractRoutingDataSource繼承自AbstractDataSource ，AbstractDataSource 實現了javax.sql.DataSource接口，所以我們的MultipleDataSource也實現了javax.sql.DataSource接口，可以賦值給sqlSessionFactory的dataSource屬性

public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
}

public abstract class AbstractDataSource implements DataSource {
}

再來說下MultipleDataSource的實現原理，MultipleDataSource實現AbstractRoutingDataSource抽象類，然后實現了determineCurrentLookupKey方法，這個方法用於選擇具體使用targetDataSources中的哪一個數據源

<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設置了兩個屬性defaultTargetDataSource和targetDataSources，這兩個屬性定義在AbstractRoutingDataSource，當MyBatis執行查詢時會先選擇數據源，選擇順序時現根據determineCurrentLookupKey方法返回的值到targetDataSources中去找，若能找到怎返回對應的數據源，若找不到返回默認的數據源defaultTargetDataSource，具體參考AbstractRoutingDataSource的源碼

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();
　　
　　.............

}

在動態切換數據源方法時選擇了AOP方式實現，這里實現的簡單粗暴，具體應用時根據實際需要靈活變通吧