@Configuration中@Autowired private DataSource rabbitProducerDataSource;

@Slf4j
@Configuration
@PropertySource({"classpath:rabbit-producer-message.properties"})
public class RabbitProducerDataSourceConfiguration {

   /**赋值*/
   @Value("${rabbit.producer.druid.type}")
   private Class<? extends DataSource> dataSourceType;

   /**给DataSource rabbitProducerDataSource 起个名字*/
   @Bean(name ="rabbitProducerDataSource")


   /*
    Spring boot有多个数据源时, 必须有一个是primary的, 否则无法启动.
     一般我们设置某个bean为primary时, 是添加primary注解
    */
   @ConfigurationProperties(prefix = "rabbit.producer.druid.jdbc")
   public DataSource rabbitProducerDataSource() throws SQLException {
      DataSource rabbitProducerDataSource = DataSourceBuilder.create().type(dataSourceType).build();
      log.info("============= rabbitProducerDataSource : {} ================", rabbitProducerDataSource);
      return rabbitProducerDataSource;
   }

   public DataSourceProperties primaryDataSourceProperties(){
      return new DataSourceProperties();
   }

   /**用于备份*/
   public DataSource primaryDataSource(){
      return primaryDataSourceProperties().initializeDataSourceBuilder().build();
   }

}

@Configuration
@AutoConfigureAfter(value = {RabbitProducerDataSourceConfiguration.class})
public class RabbitProducerMyBatisConfiguration {

   @Resource(name= "rabbitProducerDataSource")
   private DataSource rabbitProducerDataSource;

   @Bean(name="rabbitProducerSqlSessionFactory")            //自动注入上面 private DataSource rabbitProducerDataSource 入参
   public SqlSessionFactory rabbitProducerSqlSessionFactory(DataSource rabbitProducerDataSource) {
      
      SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
      bean.setDataSource(rabbitProducerDataSource);
      ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
      try {
         bean.setMapperLocations(resolver.getResources("classpath:mapper/*.xml"));
         SqlSessionFactory sqlSessionFactory = bean.getObject();
         if (sqlSessionFactory != null) {
            sqlSessionFactory.getConfiguration().setCacheEnabled(Boolean.TRUE);
         }
         return sqlSessionFactory;
      } catch (Exception e) {
         throw new RuntimeException(e);
      }
   }
   
   @Bean(name="rabbitProducerSqlSessionTemplate")
   public SqlSessionTemplate rabbitProducerSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
      return new SqlSessionTemplate(sqlSessionFactory);
   }
   
}

@Configuration
public class BrokerMessageConfiguration {

    @Autowired
    private DataSource rabbitProducerDataSource;

    /**sql 脚本*/
    @Value("classpath:rabbit-producer-message-schema.sql")
    private Resource schemaScript;
    
    @Bean
    public DataSourceInitializer initDataSourceInitializer() {
       System.err.println("--------------rabbitProducerDataSource-----------:" + rabbitProducerDataSource);
        final DataSourceInitializer initializer = new DataSourceInitializer();
        //set数据源 创建jdbc 连接
        initializer.setDataSource(rabbitProducerDataSource);
        //执行脚本sql语句   （填充器）
        initializer.setDatabasePopulator(databasePopulator());
        return initializer;
    }

    private DatabasePopulator databasePopulator() {
        final ResourceDatabasePopulator populator = new ResourceDatabasePopulator();
        populator.addScript(schemaScript);
        return populator;
    }
}

这里有三个@Configuration修饰的类, 

@Configuration
@AutoConfigureAfter(value = {RabbitProducerDataSourceConfiguration.class})
public class RabbitProducerMyBatisConfiguration {
//此类在 加载前有条件 @AutoConfigureAfter(value = {RabbitProducerDataSourceConfiguration.class})
要等到这个配置类先加载 然后在执行 这样能保证  @Resource(name= "rabbitProducerDataSource") 可以被注入

 @Resource(name= "rabbitProducerDataSource")
   private DataSource rabbitProducerDataSource;

....
....
...

}

@Configuration
public class BrokerMessageConfiguration {
//此类为什么不加 @AutoConfigureAfter(value = {RabbitProducerDataSourceConfiguration.class})
能保证@Autowired 注入的数据源是 RabbitProducerDataSourceConfiguration 这个类声明的
 @Bean(name ="rabbitProducerDataSource")


    @Autowired
    private DataSource rabbitProducerDataSource;
}

还请希望详细解答一下