使用@import导入实现了ImportBeanDefinitionRegistrar接口的类，不能被注册为bean

@Import({DataSourceRegister.class,A.class})
@SpringBootApplication
@ComponentScan("com.viewhigh.bi")
//@EnableCaching
public class BiApplication {
    public static void main(String[] args) {
        LogUtil.setEnabled(true);//开启日志输出

        SpringApplication sa = new SpringApplication(BiApplication.class);
        sa.setBannerMode(Banner.Mode.LOG);
        sa.run(args);
    }
}

public class DataSourceRegister<T> implements EnvironmentAware, ImportBeanDefinitionRegistrar {
    private javax.sql.DataSource defaultTargetDataSource;
    static final String MAINDATASOURCE = "mainDataSource";

    public final void setEnvironment(Environment environment) {
        DruidEntity druidEntity = FileUtil.readYmlByClassPath("db_info", DruidEntity.class);

        defaultTargetDataSource = DataSourceUtil.createMainDataSource(druidEntity);
    }

    public final void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry beanDefinitionRegistry) {
        // 0.将主数据源添加到数据源集合中
        DataSourceSet.putTargetDataSourcesMap(MAINDATASOURCE, defaultTargetDataSource);
        //1.创建DataSourceBean
        GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
        beanDefinition.setBeanClass(DataSource.class);
        beanDefinition.setSynthetic(true);
        MutablePropertyValues mpv = beanDefinition.getPropertyValues();
        //spring名称约定为defaultTargetDataSource和targetDataSources
        mpv.addPropertyValue("defaultTargetDataSource", defaultTargetDataSource);
        mpv.addPropertyValue("targetDataSources", DataSourceSet.getTargetDataSourcesMap());
        beanDefinitionRegistry.registerBeanDefinition("dataSource", beanDefinition);
    }
}

public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        FailureAnalyzers analyzers = null;
        this.configureHeadlessProperty();
        SpringApplicationRunListeners listeners = this.getRunListeners(args);
        listeners.starting();

        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
            Banner printedBanner = this.printBanner(environment);
            context = this.createApplicationContext();
            new FailureAnalyzers(context);
            this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
            this.refreshContext(context);
            this.afterRefresh(context, applicationArguments);
            listeners.finished(context, (Throwable)null);
            stopWatch.stop();
            if(this.logStartupInfo) {
                (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
            }

            return context;
        } catch (Throwable var9) {
            this.handleRunFailure(context, listeners, (FailureAnalyzers)analyzers, var9);
            throw new IllegalStateException(var9);
        }
    }

context = this.createApplicationContext();
this.refreshContext(context);

@Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset ‘active‘ flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // Reset common introspection caches in Spring‘s core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
            }
        }
    }