Configuring Multiple Data Sources in Spring Boot with MyBatis

Starting from BeanFactory, the article explains how Spring integrates MyBatis by injecting MyBatis beans via Spring's FactoryBean, with SqlSessionFactoryBean being the key component.

It then describes how to configure Spring Boot to use multiple data sources, defining separate datasource properties (primary and slave) and replacing the default datasource configuration.

Key dependencies include spring-boot-starter-web, mybatis-spring-boot-starter, mysql-connector-java, and druid-spring-boot-starter.

The project structure contains separate DAO packages for each datasource and a configuration class that creates DataSource, SqlSessionFactory, and SqlSessionTemplate beans for each source.

@Configuration
@MapperScan(basePackages = "com.example.dao1", sqlSessionFactoryRef = "sqlSessionFactory1")
public class DataSource1Config {
    @Bean
    @ConfigurationProperties(prefix = "spring.primary")
    public DataSource dataSourcePrimary() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    public SqlSessionFactory sqlSessionFactory1() throws Exception {
        SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
        sessionFactoryBean.setDataSource(dataSourcePrimary());
        String locationPattern = "classpath*:/mapperPrimary/*.xml";
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        sessionFactoryBean.setMapperLocations(resolver.getResources(locationPattern));
        return sessionFactoryBean.getObject();
    }

    @Bean(name = "sqlSessionTemplate1")
    public SqlSessionTemplate sqlSessionTemplate1(@Qualifier("sqlSessionFactory1") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

A similar configuration is created for the secondary datasource (slave).

@RestController
@RequestMapping("/data")
public class DataSourceController {
    @Autowired
    private User1Mapper userMapper;
    @Autowired
    private User2Mapper user2Mapper;

    @GetMapping("/get-user1/{name}")
    public User getUserFromTestDb(@PathVariable("name") String userName) {
        return userMapper.selectUser(userName);
    }

    @GetMapping("/get-user2/{name}")
    public User getUserFromTestDb2(@PathVariable("name") String userName) {
        return user2Mapper.selectUser(userName);
    }
}

The article concludes with a summary of the main components: DataSource, SqlSessionFactory, @MapperScan, and the overall flow for integrating Spring Boot with MyBatis to handle multiple databases.