Spring+Mybatis连接多个数据库

1.需求

开发先从需求或项目情况说起，

1. 项目用到几个简单的数据库和表，但是因为库和表简单，所以都配置在一个mapper里面。也即，一个mapper，需要对应多个数据库。
2. 数据库配置文件要放在最终生成的可执行jar同目录下的config文件里，跟其它设备的相关配置一起放在connection.properties文件中。

2.开发与设计

2.1 数据库配置信息

屏蔽了ip信息

jdbc.driver=com.mysql.jdbc.Driver
source.jdbc.url=jdbc:mysql://192.168.**.**:3306/Source?autoReconnect=true&connectTimeout=5000
antennapara.jdbc.url=jdbc:mysql://192.168.**.**:3306/AntennaPara?autoReconnect=true&connectTimeout=5000
tsys.jdbc.url=jdbc:mysql://192.168.**.**:3306/Tcal?autoReconnect=true&connectTimeout=5000
jdbc.username=root
jdbc.password=root

2.2 applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans-3.2.xsd 
		http://www.springframework.org/schema/mvc 
		http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd 
		http://www.springframework.org/schema/context 
		http://www.springframework.org/schema/context/spring-context-3.2.xsd 
		http://www.springframework.org/schema/aop 
		http://www.springframework.org/schema/aop/spring-aop-3.2.xsd 
		http://www.springframework.org/schema/tx 
		http://www.springframework.org/schema/tx/spring-tx-3.2.xsd ">

  <!-- 配置信息放在同目录下的config/connection.properties中，需要用file而不是classspath-->
	<context:property-placeholder location="file:./config/connection.properties"/>
	 <!-- 配置数据库1-->
	<bean id="sourceDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
		<property name="driverClassName" value="${jdbc.driver}" />
		<property name="url" value="${source.jdbc.url}" />
		<property name="username" value="${jdbc.username}" />
		<property name="password" value="${jdbc.password}" />
		<property name="maxActive" value="10"/>
		<property name="maxIdle" value="5"/>
	</bean>
	 <!-- 配置数据库2-->
	<bean id="antennaparaDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
		<property name="driverClassName" value="${jdbc.driver}" />
		<property name="url" value="${antennapara.jdbc.url}" />
		<property name="username" value="${jdbc.username}" />
		<property name="password" value="${jdbc.password}" />
		<property name="maxActive" value="10"/>
		<property name="maxIdle" value="5"/>
	</bean>
	 <!-- 配置数据库3-->
	<bean id="tsysDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
		<property name="driverClassName" value="${jdbc.driver}" />
		<property name="url" value="${tsys.jdbc.url}" />
		<property name="username" value="${jdbc.username}" />
		<property name="password" value="${jdbc.password}" />
		<property name="maxActive" value="10"/>
		<property name="maxIdle" value="5"/>
	</bean>
	 <!-- 动态数据库，**.**.**.DatabaseContextHolder 屏蔽了包名，为具体选择数据库的类 -->
	<bean id="dataSource" class="**.**.**.DatabaseContextHolder">
        <property name="defaultTargetDataSource" ref="sourceDataSource"/>
        <property name="targetDataSources">
            <map>
                <entry key="sourceDataSource" value-ref="sourceDataSource"/>
                <entry key="antennaparaDataSource" value-ref="antennaparaDataSource"/>
                <entry key="tsysDataSource" value-ref="tsysDataSource"/>
            </map>
        </property>
    </bean>
		 <!-- 因为mybatis配置里面没有设置什么内容，所以就先屏蔽掉了 -->
	<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
	<!-- 	<property name="configLocation" value="mybatis/SqlMapConfig.xml"/> -->
		<property name="dataSource" ref="dataSource"/>
	</bean>
	
		 <!-- 屏蔽了包名 -->
	<bean id="mapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
		<property name="mapperInterface" value="**.**.**.Mapper"></property>
		<property name="sqlSessionFactory" ref="sqlSessionFactory"></property>
	</bean>
	
</beans>

2.3 DatabaseContextHolder.java

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

/*
* @author: dolphinZhao
* @date:Aug 28, 2019
* @version:
* @description:
*/
public class DatabaseContextHolder extends AbstractRoutingDataSource{
	
	public static final ThreadLocal<String> contextHolder = new ThreadLocal<String>();

    public static void setSelectedDatabase(String databaseName){
        contextHolder.set(databaseName);
    }
    public static String getSelectedDatabase(){
        String databaseName= (String)contextHolder.get();
        return dbType;
    }
    public void clearContext(){
        contextHolder.remove();
    }

	@Override
	protected Object determineCurrentLookupKey() {
		return DatabaseContextHolder.getSelectedDatabase();
	}
}

2.4 使用

DatabaseContextHolder.setDbType("sourceDataSource");
Mapper mapper = (Mapper) ac.getBean("mapper");
//调用mapper完成具体操作

3 参考文献

【1】https://blog.youkuaiyun.com/u010716879/article/details/78459529
【2】https://blog.youkuaiyun.com/qq_31305965/article/details/99747686