Springboot创建容器和创建bean

　　Springboot框架的最主要类就是SpringApplication，最重要的注解是@SpringBootApplication。简单归纳一下，SpringApplication.run()作用是创建springContext，而@SpringBootAppcation的作用就是自动创建bean，被spring管理，包括tomcat容器。

@SpringBootApplication
public class Msv1Application{
    public static void main(String[] args) {
        SpringApplication.run(Msv1Application.class,args);
    }
}

那么为什么SpringBoot可以自动注入我们需要的对象呢？比如SqlSessionFactory，尤其是Tomcat容器呢？这是AutoEnableConfiguration注解的作用，看其源码，ImportSelector接口的selectImports返回的数组（类的全类名）都会被纳入到spring容器中.

public class AutoConfigurationImportSelector
        implements DeferredImportSelector, BeanClassLoaderAware, ResourceLoaderAware,
        BeanFactoryAware, EnvironmentAware, Ordered  //看这个类实现的接口多复杂

@Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        if (!isEnabled(annotationMetadata)) {
            return NO_IMPORTS;
        }
        AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
                .loadMetadata(this.beanClassLoader);
        AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(
                autoConfigurationMetadata, annotationMetadata);
        return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
    }