给我一个springboot使用druid的多数据源的例字

好的，以下是一个使用Spring Boot和Druid实现多数据源的示例：

首先，在pom.xml文件中添加依赖：

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid-spring-boot-starter</artifactId>
    <version>1.2.6</version>
</dependency>

然后，在application.properties或application.yml文件中配置Druid的数据源：

spring:
  datasource:
    master:
      driver-class-name: com.mysql.jdbc.Driver
      url: jdbc:mysql://localhost:3306/master_db?useUnicode=true&characterEncoding=utf-8
      username: root
      password: root
      type: com.alibaba.druid.pool.DruidDataSource
      initialSize: 5
      minIdle: 5
      maxActive: 20
      maxWait: 60000
    slave:
      driver-class-name: com.mysql.jdbc.Driver
      url: jdbc:mysql://localhost:3306/slave_db?useUnicode=true&characterEncoding=utf-8
      username: root
      password: root
      type: com.alibaba.druid.pool.DruidDataSource
      initialSize: 5
      minIdle: 5
      maxActive: 20
      maxWait: 60000

接下来，创建两个数据源的配置类：

@Configuration
@MapperScan(basePackages = "com.example.demo.mapper.master", sqlSessionTemplateRef = "masterSqlSessionTemplate")
public class MasterDataSourceConfig {

    @Bean(name = "masterDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DataSource dataSource() {
        return DruidDataSourceBuilder.create().build();
    }

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

    @Bean(name = "masterTransactionManager")
    public DataSourceTransactionManager transactionManager(@Qualifier("masterDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "masterSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("masterSqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

@Configuration
@MapperScan(basePackages = "com.example.demo.mapper.slave", sqlSessionTemplateRef = "slaveSqlSessionTemplate")
public class SlaveDataSourceConfig {

    @Bean(name = "slaveDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DataSource dataSource() {
        return DruidDataSourceBuilder.create().build();
    }

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

    @Bean(name = "slaveTransactionManager")
    public DataSourceTransactionManager transactionManager(@Qualifier("slaveDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "slaveSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("slaveSqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

最后，在需要使用的Mapper类中指定使用哪个数据源：

@Repository
public interface UserMapper {
    
    // 使用master数据源
    @DataSource("masterDataSource")
    List<User> selectAllFromMaster();
    
    // 使用slave数据源
    @DataSource("slaveDataSource")
    List<User> selectAllFromSlave();
}

这样就可以通过@DataSource注解来动态切换数据源了。