前言

我们配置主从数据源的时候，就需要多数据源配置。

application.properties 方式配置

#数据库连接 Master
spring.datasource.master.username=root
spring.datasource.master.password=12345678
spring.datasource.master.jdbc-url=jdbc:mysql://localhost:3308/h5_db?characterEncoding=utf-8
spring.datasource.master.driver-class-name=com.mysql.cj.jdbc.Driver
#数据库连接 Slave
spring.datasource.slave.username=user
spring.datasource.slave.password=12345678
spring.datasource.slave.jdbc-url=jdbc:mysql://localhost:3307/h5_db?characterEncoding=utf-8
spring.datasource.slave.driver-class-name=com.mysql.cj.jdbc.Driver

代码

@Configuration
public class DataSourceConfig {@Bean@ConfigurationProperties("spring.datasource.master")public DataSource masterDataSource() {return DataSourceBuilder.create().build();}@Bean@ConfigurationProperties("spring.datasource.slave")public DataSource slaveDataSource() {return DataSourceBuilder.create().type(HikariDataSource.class).build();}@Primary@Beanpublic DynamicDataSource dataSource(@Qualifier("masterDataSource") DataSource masterDataSource,@Qualifier("slaveDataSource") DataSource slaveDataSource) {Map<Object, Object> dataSourceMap = new HashMap<>();dataSourceMap.put(DataSourceType.Master, masterDataSource);dataSourceMap.put(DataSourceType.Slave, slaveDataSource);DynamicDataSource dataSource = new DynamicDataSource();dataSource.setTargetDataSources(dataSourceMap);dataSource.setDefaultTargetDataSource(masterDataSource());dataSource.afterPropertiesSet();return dataSource;}
}

bean.xml 方式配置

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><bean id="masterDataSource" class="com.zaxxer.hikari.HikariDataSource" destroy-method="close"><property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/><property name="jdbcUrl"value="jdbc:mysql://localhost:3308/h5_db?characterEncoding=utf-8"/><property name="username" value="root"/><property name="password" value="12345678"/></bean><bean id="slaveDataSource" class="com.zaxxer.hikari.HikariDataSource" destroy-method="close"><property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/><property name="jdbcUrl"value="jdbc:mysql://localhost:3307/h5_db?characterEncoding=utf-8"/><property name="username" value="user"/><property name="password" value="12345678"/></bean><bean id="dataSource" class="com.ysp.template.route.DynamicDataSource" primary="true"><property name="targetDataSources"><map key-type="java.lang.String"><entry key="master" value-ref="masterDataSource"/><entry key="slave" value-ref="slaveDataSource"/></map></property><property name="defaultTargetDataSource" ref="masterDataSource"/></bean></beans>

多数据源设置默认数据源

此外使用primary="true"设置默认数据源为动态数据源。SpringBoot自动装配SqlSessionFactory和DataSourceTransactionManager时注入的都是动态数据源。就不需要代码配置。
重点：配置多数据源强烈建议过滤数据源自动配置
过滤代码

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})

SqlSessionFactory配置
xml方式

    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"><property name="dataSource" ref="dataSource"/><property name="configLocation" value="classpath:mybatis/mybatis-config.xml"/><property name="typeAliasesPackage" value="com.ysp.template.pojo.dao"/><property name="mapperLocations" value="classpath:mybatis/mapper/*.xml"/></bean>

java方式

    @Beanpublic SqlSessionFactory sqlSessionFactory(@Qualifier("dataSource") DataSource dataSource) throws Exception {System.out.println("=>>>=======>: " + dataSource.getClass().getName());SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(dataSource);bean.setConfigLocation(new ClassPathResource("mybatis/mybatis-config.xml"));bean.setTypeAliasesPackage("com.ysp.template.pojo.dao");bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mybatis/mapper/*.xml"));return bean.getObject();}

动态数据源切换

重点：ThreadLocal 和 AbstractRoutingDataSource 使用

AbstractRoutingDataSource 源码

org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource

    // 获取数据库连接public Connection getConnection() throws SQLException {return this.determineTargetDataSource().getConnection();}// 切换数据源protected DataSource determineTargetDataSource() {Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");Object lookupKey = this.determineCurrentLookupKey();DataSource 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 + "]");} else {return dataSource;}}// 重新这个方法，返回数据源标示Key就可以动态切换@Nullableprotected abstract Object determineCurrentLookupKey();    

代码

public class DataSourceHandler {private static ThreadLocal<String> datasourceContext = new ThreadLocal<>();public static void switchDataSource(String datasource) {System.out.println("switchDataSource: " + datasource);datasourceContext.set(datasource);}public static String getDataSource() {return datasourceContext.get();}public static void clear() {datasourceContext.remove();}
}

public class DynamicDataSource extends AbstractRoutingDataSource {@Overrideprotected Object determineCurrentLookupKey() {//System.out.println(">>>>>>>>>>>>>: determineCurrentLookupKey");return DataSourceHandler.getDataSource();}
}

@Target({METHOD, TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface DataSource {String value() default "";
}

@Aspect
@Component
@Order(1) // 重点：当使用事务注解（@Transactional）的时候，切换数据源aop要优先事务执行。
public class DataSourceAspect {@Pointcut("@annotation(com.ysp.template.annotation.DataSource)")public void pointcut() {}@Before(value = "pointcut()")public void switchDataSource(JoinPoint joinPoint) {//从切面织入点处通过反射机制获取织入点处的方法MethodSignature signature = (MethodSignature) joinPoint.getSignature();//获取切入点所在的方法Method method = signature.getMethod();DataSource annotation = method.getAnnotation(DataSource.class);DataSourceHandler.switchDataSource(annotation.value());}@After(value = "pointcut()")  // 必须加@Afterpublic void clear(){DataSourceHandler.clear();}
}

注解动态切换数据源

    @Transactional@DataSource(DataSourceType.Master)public String addProject(ProjectDo projectDo, List<ProjectMemberDo> projectMembers) {return addProjectPrivate(projectDo, projectMembers);}

断点跟踪源码验证切换

1、首先是AbstractRoutingDataSource类

2、DataSourceTransactionManager

org.springframework.jdbc.datasource.DataSourceTransactionManager

    protected void doBegin(Object transaction, TransactionDefinition definition) {DataSourceTransactionManager.DataSourceTransactionObject txObject = (DataSourceTransactionManager.DataSourceTransactionObject)transaction;Connection con = null;// 中间省略了，主要逻辑，事务获取数据源连接。此处需要断点。}

3、DataSourceTransactionManagerAutoConfiguration
1、事务自动配置类：我们在这里打断点查看数据源是否是动态数据源（DynamicDataSource）
2、如果我们代码自己配置事务建议过滤调事务自动配置

@SpringBootApplication(exclude = {DataSourceTransactionManagerAutoConfiguration.class})

源码

    @ConditionalOnSingleCandidate(DataSource.class)static class DataSourceTransactionManagerConfiguration {DataSourceTransactionManagerConfiguration() {}@Bean@ConditionalOnMissingBean({PlatformTransactionManager.class})DataSourceTransactionManager transactionManager(DataSource dataSource, ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers) {// DataSource dataSource 是否为DynamicDataSourceDataSourceTransactionManager transactionManager = new DataSourceTransactionManager(dataSource);transactionManagerCustomizers.ifAvailable((customizers) -> {customizers.customize(transactionManager);});return transactionManager;}}

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