目前最优的方式是，注入多个datasource 然后通过org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource在执行得时候设置根据key设置当前上下文不同的datasource，通过@Primary设置实现类为默认数据源。在事务中不支持数据源切换，因为事务默认不是分布式不跨库的。

下面这是为不同mapper设置不同datasource的方式，不优雅。

@Configuration
@MapperScan(basePackages = "com.activitytomongo.mapper", sqlSessionTemplateRef = "promoteSqlSessionTemplate")
public class PromoteDatasourceConfig {
	
	@Bean(name = "promoteDatasource")
	@ConfigurationProperties(prefix = "spring.datasource.promote")
	public DataSource setPromoteDataSource() {
		return DataSourceBuilder.create().build();
	}

	@Bean(name = "promoteTransactionManager")
	public PlatformTransactionManager promoteSqlSessionTemplate(@Qualifier("promoteDatasource") DataSource dataSource) {
		return new DataSourceTransactionManager(dataSource);
	}

	@Bean(name = "promoteSqlSessionFactory")
	public SqlSessionFactory promoteSqlSessionFactory(@Qualifier("promoteDatasource") DataSource dataSource) throws Exception {
		SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
		bean.setDataSource(dataSource);
		return bean.getObject();
	}

	@Bean(name = "promoteSqlSessionTemplate")
	public SqlSessionTemplate setSqlSessionTemplate(
			@Qualifier("promoteSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
		// return new SqlSessionTemplate(sqlSessionFactory);
		return new SqlSessionTemplate(sqlSessionFactory, ExecutorType.BATCH);
	}
}