Spring+MyBatis多数据源配置实现(AbstractRoutingDataSource)

布满荆棘的人生 2022-07-17 02:12 242阅读 0赞

在spring 中，一个很好用但是容易被忽略的，就是AbstractRoutingDataSource，它的一个作用就是可以根据用户发起的不同请求去转换不同的数据源，比如根据用户的不同地区语言选择不同的数据库，下面举例说明：

单数据源时的Spring配置文件

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<? xml version="1.0" encoding="UTF-8" ?>

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>
    
        
        <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
            <property name="basePackage" value="com.cnblogs.lzrabbit"/>
        </bean>
    
        
        <context:component-scan base-package="com.cnblogs.lzrabbit"/>
        <aop:aspectj-autoproxy/>
    </beans>

MultipleDataSource实现

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();
        }
    }

MyBatis接口Mapper定义，直接使用注解方式实现

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

手动数据源切换调用

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);
            
            //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();
        }
    }

使用SpringAOP方式实现自动切换

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();
        }
    }

调用日志

2014-05-25 20:02:04,319 DEBUG [main] com.cnblogs.lzrabbit.MySqlMapper.getList - ooo Using Connection [jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true, UserName=root@192.168.1.32, MySQL Connector Java]
    2014-05-25 20:02:04,333 DEBUG [main] com.cnblogs.lzrabbit.MySqlMapper.getList - ==>  Preparing: select * from MyTable 
    2014-05-25 20:02:04,371 DEBUG [main] com.cnblogs.lzrabbit.MySqlMapper.getList - ==> Parameters: 
    2014-05-25 20:02:04,396 DEBUG [main] com.cnblogs.lzrabbit.MySqlMapper.getList - <==      Total: 8
    2014-05-25 20:02:04,620 DEBUG [main] com.cnblogs.lzrabbit.SqlServerMapper.getList - ooo Using Connection [jdbc:jtds:sqlserver://127.0.0.1:1433/test, UserName=sa, jTDS Type 4 JDBC Driver for MS SQL Server and Sybase]
    2014-05-25 20:02:04,620 DEBUG [main] com.cnblogs.lzrabbit.SqlServerMapper.getList - ==>  Preparing: select * from TmallCityMap 
    2014-05-25 20:02:04,621 DEBUG [main] com.cnblogs.lzrabbit.SqlServerMapper.getList - ==> Parameters: 
    2014-05-25 20:02:04,681 DEBUG [main] com.cnblogs.lzrabbit.SqlServerMapper.getList - <==      Total: 397

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

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

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

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

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