首先创建一个配置类

@Configuration  //告诉spring这是一个配置类
@ComponentScan(value = "cn.yb") //扫描包，controller，service等，不然只有@bean里的组件
public class MainConfig {
    @Bean
    public Person person(){
        System.out.println("person");
        return new Person();
    }
    @Bean
    @Lazy  //懒加载，只有在第一次使用的时候才会初始化
            // 因为在单例模式下，在容器创建的时候就加载了组件
            //原型模式下，组件在调用时才会创建
    public Person person2(){
        System.out.println("person2");
        return new Person("person2",11);
    }
}

在定义的两个controller类

@Controller
public class Controller1 {
    public void test1(){
        System.out.println("test1");
    }
}

@Controller
public class Controller2 {
    public void test2(){
        System.out.println("test2");
    }
}

测试类

public class SpringTest {
    public static void main(String[] args) {
        //根据配置类来获取容器
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext("cn.yb.config");
       // AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(MainConfig.class);

        Person person = applicationContext.getBean(Person.class);
        System.out.println(person);

        String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
        for (String beanDefinitionName : beanDefinitionNames) {
            System.out.println(beanDefinitionName);
        }
    }
}

开始调试：
首先创建容器，所谓的容器，并不是说里面只有bean,还有beanDefinition等，只是一个环境，bean的扫描，解析，实例化，初始化都在这个环境里进行。

spring1.png

AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext("cn.yb.config");

1.进入AnnotationConfigApplicationContext的构造函数

    public AnnotationConfigApplicationContext(String... basePackages) {
        this();
        //扫描配置文件，并会将配置类放入BeanFactory中
        scan(basePackages);
        refresh();
    }

1.1this():空参的构造函数，此时会有一个隐藏的super()

    public AnnotationConfigApplicationContext() {
        this.reader = new AnnotatedBeanDefinitionReader(this);
        this.scanner = new ClassPathBeanDefinitionScanner(this);
    }

1.1.1super():GenericApplicationContext类中，在这里会创建一个DefaultListableBeanFactory

    public GenericApplicationContext() {
        this.beanFactory = new DefaultListableBeanFactory();
    }

DefaultListableBeanFactory:里面有个 Map<beanName,beanDefinition>保存bean

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
        implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
/** Map of bean definition objects, keyed by bean name */
    private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

beanDefinition：就是一个描述bean的类，里面有bean的各种属性（那为什么不用bean呢？而用beanDefinition来描述一个bean对象，spring就是这么命名哒，hhhhh）

spring2.png

1.2scan(basePackages) //扫描配置文件，并会将配置类放入BeanFactory中

spring3.png

spring4.png

1.3 refresh():刷新容器

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();
            }
        }
    }

其中最主要是的有两个方法：
1、invokeBeanFactoryPostProcessors(beanFactory) 在这里进行bean的扫描和解析工作，保存在beanFactory中的BeanDefinitionMap中

spring5.png

2.finishBeanFactoryInitialization(beanFactory);在这里进行对bean的创建，实例化