public interface ImportSelector {

    /**
     * Select and return the names of which class(es) should be imported based on
     * the {@link AnnotationMetadata} of the importing @{@link Configuration} class.
     */
    String[] selectImports(AnnotationMetadata importingClassMetadata);

}

看一下該介面，註釋說明，實現該介面的selectImport則返回的String[]的 class字串 類將被註冊為@Configuration，即只要實現該介面返回的類將被注入Spring容器。@see ImportBeanDefinitionRegistrar則說明是使用 ImportBeanDefinitionRegistrar的registerBeanDefinitions方法進行注入。看一下其直接繼承的子類關係圖：

大致分為五類（後續分析其他原始碼需要）：
Spring boot的自動裝配、測試、快取自動裝配、web相關。
Spring的aop相關的：@EnableTransactionManagement、@Async、@EnableCaching
下面以@EnableTransactionManagement主線進行梳理
只是從註釋看是通過ImportBeanDefinitionRegistrar進行注入的，但是今天梳理了一下，發現源頭還是從ApplicationContext的refresh模板模式方法（可以參見模板方法模式-簡單實現和Spring中的使用分析）開始。

@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();
        }
    }
}

模板方法第五步就是：