Springboot整合了Mybatis，mybatis-config.xml可以省略不写，如何配置多数据源

在Spring Boot中，配置多数据源可以通过以下步骤实现：

1. 在`application.properties`或`application.yml`中配置多个数据源的相关属性，例如：

spring:
  datasource:
    master:
      url: jdbc:mysql://localhost:3306/master_db
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver
    slave:
      url: jdbc:mysql://localhost:3306/slave_db
      username: root
      password: root
      driver-class-name: com.mysql.jdbc.Driver

2. 创建多个数据源的实例，并将它们注入到`SqlSessionFactory`中：

@Configuration
public class MybatisConfig {
    
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DataSource masterDataSource() {
        return DataSourceBuilder.create().build();
    }
    
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DataSource slaveDataSource() {
        return DataSourceBuilder.create().build();
    }
    
    @Bean
    public SqlSessionFactory masterSqlSessionFactory(@Qualifier("masterDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        return factoryBean.getObject();
    }
    
    @Bean
    public SqlSessionFactory slaveSqlSessionFactory(@Qualifier("slaveDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        return factoryBean.getObject();
    }
}

3. 配置`@MapperScan`注解扫描多个`Mapper`接口所在的包路径，并指定对应的`SqlSessionFactory`：

@Configuration
@MapperScan(basePackages = "com.example.mapper.master", sqlSessionFactoryRef = "masterSqlSessionFactory")
public class MasterDataSourceConfig {
}

@Configuration
@MapperScan(basePackages = "com.example.mapper.slave", sqlSessionFactoryRef = "slaveSqlSessionFactory")
public class SlaveDataSourceConfig {
}

这样就可以在应用中使用多个数据源了。在需要访问不同数据源的`Mapper`接口方法上，可以使用`@Qualifier`注解指定对应的`SqlSessionFactory`，例如：

@Service
public class UserService {
    
    @Autowired
    @Qualifier("masterSqlSessionFactory")
    private SqlSessionFactory masterSqlSessionFactory;
    
    @Autowired
    @Qualifier("slaveSqlSessionFactory")
    private SqlSessionFactory slaveSqlSessionFactory;
    
    public User getMasterUserById(int id) {
        try (SqlSession sqlSession = masterSqlSessionFactory.openSession()) {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            return userMapper.getById(id);
        }
    }
    
    public User getSlaveUserById(int id) {
        try (SqlSession sqlSession = slaveSqlSessionFactory.openSession()) {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            return userMapper.getById(id);
        }
    }
}