Spring如何为多数据源配置多个事务管理器？

1.配置多个数据源

配置多个数据源的信息，可以使用xml、json、配置中心、zookeeper、数据库加载等多种方式，例如在application.properties中配置多个数据源：

# 数据源1
spring.datasource.db1.url=jdbc:mysql://localhost:3306/db1?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
spring.datasource.db1.username=root
spring.datasource.db1.password=root
spring.datasource.db1.driver-class-name=com.mysql.jdbc.Driver# 数据源2
spring.datasource.db2.url=jdbc:mysql://localhost:3306/db2?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
spring.datasource.db2.username=root
spring.datasource.db2.password=root
spring.datasource.db2.driver-class-name=com.mysql.jdbc.Driver

2.创建数据源配置类

分别创建两个数据源配置类，并分别指定数据源配置前缀：

@Configuration
public class DataSourceConfig {@Bean(name = "db1DataSource")@ConfigurationProperties(prefix = "spring.datasource.db1")public DataSource db1DataSource() {return DataSourceBuilder.create().build();}@Bean(name = "db2DataSource")@ConfigurationProperties(prefix = "spring.datasource.db2")public DataSource db2DataSource() {return DataSourceBuilder.create().build();}
}

3.创建多个事务管理器

创建两个事务管理器，并分别指定对应的数据源：

@Configuration
public class TransactionManagerConfig {@Autowired@Qualifier("db1DataSource")private DataSource db1DataSource;@Autowired@Qualifier("db2DataSource")private DataSource db2DataSource;@Bean(name = "db1TransactionManager")public DataSourceTransactionManager db1TransactionManager() {return new DataSourceTransactionManager(db1DataSource);}@Bean(name = "db2TransactionManager")public DataSourceTransactionManager db2TransactionManager() {return new DataSourceTransactionManager(db2DataSource);}
}

4.创建多个JdbcTemplate

创建两个JdbcTemplate，并分别指定对应的数据源：

@Configuration
public class JdbcTemplateConfig {@Autowired@Qualifier("db1DataSource")private DataSource db1DataSource;@Autowired@Qualifier("db2DataSource")private DataSource db2DataSource;@Bean(name = "db1JdbcTemplate")public JdbcTemplate db1JdbcTemplate() {return new JdbcTemplate(db1DataSource);}@Bean(name = "db2JdbcTemplate")public JdbcTemplate db2JdbcTemplate() {return new JdbcTemplate(db2DataSource);}
}

如果使用MyBatis，可以顺带配置一下SqlSessionFactory：

    @Bean(name = "db1SqlSessionFactory")public SqlSessionFactory db1SqlSessionFactory(@Value("${mybatis.db1.mapper-locations}") String mapperLocations) throws Exception {SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();sessionFactoryBean.setDataSource(db1DataSource);sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));// 设置MyBatis配置文件位置sessionFactoryBean.setConfigLocation(new ClassPathResource("mybatis-config.xml"));return sessionFactoryBean.getObject();}@Bean(name = "db2SqlSessionFactory")public SqlSessionFactory db2SqlSessionFactory(@Value("${mybatis.db2.mapper-locations}") String mapperLocations) throws Exception {SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();sessionFactoryBean.setDataSource(db2DataSource);sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));// 设置MyBatis配置文件位置sessionFactoryBean.setConfigLocation(new ClassPathResource("mybatis-config.xml"));return sessionFactoryBean.getObject();}

 使用事务：

    @Transactional(transactionManager = "db1TransactionManager", rollbackFor = Exception.class)public void insertDb1(String name) {db1JdbcTemplate.update("INSERT INTO test (name) VALUES (?)", name);}@Transactional(transactionManager = "db2TransactionManager", rollbackFor = Exception.class)public void insertDb2(String name) {db2JdbcTemplate.update("INSERT INTO test (name) VALUES (?)", name);}

到目前为止，一切都很顺利，问题来了：

如果架构上数据库采用主从模式，那么如何配置事务管理器？

一般主库负责写，从库负责读，事务管理器主要作用是能在异常时回滚业务代码，读数据没有回滚业务代码的必要，所以主从模式下不需要为主从数据源都配置事务管理器，只需要为主库配置事务管理即可。

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