spring源码解析一bean

　　学习spring源码是一件非常煎熬且很有挑战的事情，在我们日常的工作中用的最多的框架可能就是spring及其的拓展，这是一个极其庞大的家族，首先我们来先来学习spring源码，然后在它的基础上学习spring mvc ,springboot,spring colud等。
　　1、 BeanFactory 对bean的生命周期进行管理，生产各种所需要的bean供我们使用
　　BeanFactory是一个接口，它的子接口跟实现有：AnnotationConfigApplicationContext 是用来管理注解bean的容器；GenericApplicationContext 通用应用上下文； AnnotationConfigRegistry 注解配置注册表，ListableBeanFactory根据各种条件获取bean的配置清单；ConfigurableBeanFactory提供配置factory的各种方法
　　2、BeanFactoryPostProcessor:对beanFactory进行操作更新的类； @FunctionalInterface public interface BeanFactoryPostProcessor {     /**    * Modify the application context＂s internal bean factory after its standard    * initialization. All bean definitions will have been loaded, but no beans    * will have been instantiated yet. This allows for overriding or adding    * properties even to eager-initializing beans.    * @param beanFactory the bean factory used by the application context    * @throws org.springframework.beans.BeansException in case of errors    */   void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;   }
　　BeanFactoryPostProcessor 就一个方法 postProcessBeanFactory，看一下他的实现ConfigurationClassPostProcessor  class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,     PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
　　ConfigurationClassPostProcessor 实现了好几个接口，我们简单说一下： BeanDefinitionRegistryPostProcessor： BeanFactoryPostProcessor的子接口，在常规的BeanFactoryPostProcessor检测之前注册bean的定义信息
　　PriorityOrdered：设置优先级
　　ResourceLoaderAware：设置资源加载器，可以获取到外部资源文件
　　BeanClassLoaderAware：设置类加载器
　　EnvironmentAware：设置环境变量  /**    * 添加CGLIB增强处理及ImportAwareBeanPostProcessor后置处理类    *    * Prepare the Configuration classes for servicing bean requests at runtime    * by replacing them with CGLIB-enhanced subclasses.    */   @Override   public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {     int factoryId = System.identityHashCode(beanFactory);     if (this.factoriesPostProcessed.contains(factoryId)) {       throw new IllegalStateException(           ＂postProcessBeanFactory already called on this post-processor against ＂ + beanFactory);     }     this.factoriesPostProcessed.add(factoryId);     if (!this.registriesPostProcessed.contains(factoryId)) {   //构建和验证一个类是否被@Configuration修饰，并做相关的解析工作       processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);     }   //增强配置     enhanceConfigurationClasses(beanFactory);     //添加后置处理类     beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));   }
　　3、BeanDefinition:bean的定义描述信息；
　　从加载配置文件后生成bean定义信息，主要就是设置类名，作用域，单例还是原型，是否懒加载等
　　4、 beanPostProcessor:对初始化前后进行处理的类；
　　主要就两个方法 public interface BeanPostProcessor {      /**     * 初始化方法调用前要进行的处理逻辑     *     * Apply this {@code BeanPostProcessor} to the given new bean instance before any bean     * initialization callbacks (like InitializingBean＂s {@code afterPropertiesSet}     * or a custom init-method). The bean will already be populated with property values.     * The returned bean instance may be a wrapper around the original.     * 
The default implementation returns the given {@code bean} as-is.     * @param bean the new bean instance     * @param beanName the name of the bean     * @return the bean instance to use, either the original or a wrapped one;     * if {@code null}, no subsequent BeanPostProcessors will be invoked     * @throws org.springframework.beans.BeansException in case of errors     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet     */    @Nullable    default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {       return bean;    }      /**     * 在初始化方法指定后要进行的处理逻辑     *     * Apply this {@code BeanPostProcessor} to the given new bean instance after any bean     * initialization callbacks (like InitializingBean＂s {@code afterPropertiesSet}     * or a custom init-method). The bean will already be populated with property values.     * The returned bean instance may be a wrapper around the original.     * 
In case of a FactoryBean, this callback will be invoked for both the FactoryBean     * instance and the objects created by the FactoryBean (as of Spring 2.0). The     * post-processor can decide whether to apply to either the FactoryBean or created     * objects or both through corresponding {@code bean instanceof FactoryBean} checks.     * 
This callback will also be invoked after a short-circuiting triggered by a     * {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method,     * in contrast to all other {@code BeanPostProcessor} callbacks.     * 
The default implementation returns the given {@code bean} as-is.     * @param bean the new bean instance     * @param beanName the name of the bean     * @return the bean instance to use, either the original or a wrapped one;     * if {@code null}, no subsequent BeanPostProcessors will be invoked     * @throws org.springframework.beans.BeansException in case of errors     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet     * @see org.springframework.beans.factory.FactoryBean     */    @Nullable    default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {       return bean;    }
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