在开发过程中，可能出现需要连接多个数据库情况，此时就需要在项目中配置多数据库；
或者当前项目需要使用除当前数据以外的数据库数据作为一些基础

基础说明

1.项目使用 SpringBoot
2.数据库为两个 5.7.X的MySQL
3,Maven配置，根据版本自行调整

<!-- druid -->
<dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid-spring-boot-starter</artifactId>
      <version>1.1.10</version>
 </dependency>
 <!-- mysql -->
 <dependency>
     <groupId>mysql</groupId>
     <artifactId>mysql-connector-java</artifactId>
</dependency>

数据源配置

本项目使用yml进行配置

spring:
  datasource:
      primary:
        type: com.alibaba.druid.pool.DruidDataSource
        jdbc-url: jdbc:mysql://localhost:3306/locat_a?characterEncoding=utf8
        username: root
        password: 123
        # 数据库连接驱动
        driver-class-name: com.mysql.cj.jdbc.Driver

      secondary:
      	type: com.alibaba.druid.pool.DruidDataSource
        jdbc-url: jdbc:mysql://localhost:3306/locat_b?characterEncoding=utf8
        username: root
        password: 456
        driver-class-name: com.mysql.cj.jdbc.Driver

配置类

MySQL1配置类

@Configuration
@MapperScan(basePackages = "com.test.mapper.primary", sqlSessionTemplateRef = "MasterSqlSessionTemplate")
public class DruidPrimaryDataSourceConfig {

    @Bean(name = "masterDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    @Primary
    public DataSource testDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "MasterSqlSessionFactory")
    @Primary
    public SqlSessionFactory testSqlSessionFactory(@Qualifier("masterDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:com/test/mapper/primary/*.xml"));
        return bean.getObject();
    }

    @Bean(name = "MasterTransactionManager")
    @Primary
    public DataSourceTransactionManager testTransactionManager(@Qualifier("masterDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "MasterSqlSessionTemplate")
    @Primary
    public SqlSessionTemplate testSqlSessionTemplate(@Qualifier("MasterSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }

}

MySQL2配置类

@Configuration
@MapperScan(basePackages = "com.test.mapper.secondary", sqlSessionTemplateRef = "SalverSqlSessionTemplate")
public class DruidSecondaryDataSourceConfig {

    @Bean(name = "salverDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource testDataSource() { return DataSourceBuilder.create().build(); }

    @Bean(name = "SalverSqlSessionFactory")
    public SqlSessionFactory testSqlSessionFactory(@Qualifier("salverDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:com/test/mapper/secondary/*.xml"));
        return bean.getObject();
    }

    @Bean(name = "SalverTransactionManager")
    public DataSourceTransactionManager testTransactionManager(@Qualifier("salverDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "SalverSqlSessionTemplate")
    public SqlSessionTemplate testSqlSessionTemplate(@Qualifier("SalverSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }

}

注：
1.相同颜色的方框需要保持相同；
2.椭圆框需要保证数据存在
3.@Primary 注解，只有主数据库可以进行配置，但是不可以两个配置类都是用此注解，出现多个会报错
4.两个数据库对应的DAO需要分开，便于进行配置，也便于查找问题

补充

如果bean名称相同，需要使用别名；

@Mapper
@Component("twoUserMapper")
public interface UserMapper {
}

service层引入数据

@Autowired
@Qualifier("twoUserMapper")
private com.test.mapper.secondary.UserMapper twoUserMapper;