spring源码解析以及常见的面试题

一 概述 

  spring是一个开源框架，以ioc和aop为核心，像是java语言的一个生态，是服务端开发的基石，因为springboot，cloud等框架是以spring为基础进行开发的。

  IOC(Inversion of Controller,控制反转)，将原本在程序中手动创建对象的控制权，交由给Spring框架来管理。IOC容器是Spring用来实现IOC的载体，IOC容器实际上就是一个Map(key, value)，Map中存放的是各种对象。

IOC和DI的区别
IOC是一种实现思想，DI是具体的实现方式。它们是同一个概念不同角度的描述，只是他们的描述方向不一样

控制反转是从容器方面，容器控制应用程序的创建，并且为其提供需要调用的外部资源。
依赖注入是从应用程序方面，应用程序依赖容器进行创建，并且注入它所需要的外部资源

二 用法

略

三 源码解读(基于注解方式)

配置类：

@EnableAspectJAutoProxy
@Configuration
@ComponentScan("funnysoul.vip.service.spring.testBeanLife")
public class AppConfig {
}

 入口

new AnnotationConfigApplicationContext(AppConfig.class);

AnnotationConfigApplicationContext的继承关系图

 AnnotationConfigApplicationContext的初始化

      1先初始化AbstractApplicationContxt  

public AbstractApplicationContext() {
   this.resourcePatternResolver = getResourcePatternResolver();
}

protected ResourcePatternResolver getResourcePatternResolver() {
   return new PathMatchingResourcePatternResolver(this);
}

    2再初始化GenericApplicationContxt

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

  3本类初始化有参数

   

public AnnotationConfigApplicationContext(Class... annotatedClasses) {
   this();
   register(annotatedClasses);
   refresh();
}

 this方法 空的构造函数

      this.reader = new AnnotatedBeanDefinitionReader(this);

      主要向beanFactory接口的默认实现DefaultListableBeanFactory的beanDefinitionMap注册后置处理器 5个processor

register方法

      主要注册配置类

BeanDefinitionHolder  主要有 beanName 和BeanDefinition

BeanDefinition bean的定义信息

详解refresh方法

1.prepareRefresh();

    设置容器的开启时间和开启状态。

    校验系统属性是否缺少

    初始化监听器和事件的集合，空的

2.ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

   区别于xml的

   只是拿到beanFactory，之前已经创建好的

3，prepareBeanFactory(beanFactory);

    填充beanFactory的属性值

4，postProcessBeanFactory(beanFactory);

    空实现，留给子类扩展

5，invokeBeanFactoryPostProcessors(beanFactory);

    主要作用就是ConfigurationClassPostProcessora解析bean，填充道beanFactory，然后实例化实现了BeanFactoryPostProcessor接口的类

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
   PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
   if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
      beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
      beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
   }
}

   进入invokeBeanFactoryPostProcessors

// Invoke BeanDefinitionRegistryPostProcessors first, if any.
		Set processedBeans = new HashSet<>();

		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

			List regularPostProcessors = new ArrayList<>();
			List registryProcessors = new ArrayList<>();

			//自定义的beanFactoryPostProcessors
			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {//BeanDefinitionRegistryPostProcessor  BeanfactoryPostProcessor
					regularPostProcessors.add(postProcessor);
				}
			}

			// Do not initialize FactoryBeans here: We need to leave all regular beans
			// uninitialized to let the bean factory post-processors apply to them!
			// Separate between BeanDefinitionRegistryPostProcessors that implement
			// PriorityOrdered, Ordered, and the rest.
			//这个currentRegistryProcessors 放的是spring内部自己实现了BeanDefinitionRegistryPostProcessor接口的对象

			List currentRegistryProcessors = new ArrayList<>();

			// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
			//BeanDefinitionRegistryPostProcessor 等于 BeanFactoryPostProcessor
			//getBeanNamesForType  根据bean的类型获取bean的名字ConfigurationClassPostProcessor
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			//这个地方可以得到一个BeanFactoryPostProcessor，因为是spring默认在最开始自己注册的
			//为什么要在最开始注册这个呢？
			//因为spring的工厂需要许解析去扫描等等功能
			//而这些功能都是需要在spring工厂初始化完成之前执行
			//要么在工厂最开始的时候、要么在工厂初始化之中，反正不能再之后
			//因为如果在之后就没有意义，因为那个时候已经需要使用工厂了
			//所以这里spring'在一开始就注册了一个BeanFactoryPostProcessor，用来插手springfactory的实例化过程
			//在这个地方断点可以知道这个类叫做ConfigurationClassPostProcessor
			//ConfigurationClassPostProcessor 他能插手spring工厂的实例化过程
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			//排序不重要，况且currentRegistryProcessors这里也只有一个数据
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			//合并list，不重要(为什么要合并，因为还有自己的)
			registryProcessors.addAll(currentRegistryProcessors);
			//最重要。注意这里是方法调用
			//执行所有BeanDefinitionRegistryPostProcessor

			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			//执行完成了所有BeanDefinitionRegistryPostProcessor
			//这个list只是一个临时变量，故而要清除
			currentRegistryProcessors.clear();

			// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
			}

			// Now, invoke the postProcessBeanFactory callback of all processors handled so far
			//前面执行的BeanFactoryPostProcessor的子类BeanDefinitionRegistryPostProcessor的回调
			//这是执行的是BeanFactoryPostProcessor    postProcessBeanFactory
			//ConfuguratuonClassPpostProcssor
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			//自定义BeanFactoryPostProcessor
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);

invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);  传入的是ConfigurationClassPostProcessor

  核心方法 processConfigBeanDefinitions(BeanDefinitionRegistry registry)

      通过这个类ConfigurationClassParser循环所有的bd，看是否加了Configuration Component ComponentScan Import ImportResource注解

      通过ComponentScanAnnotationParser去得到扫描的类classPathBeanDefinitionScaner的doScan去扫描

         本质是通过PathMatchingResourcePatternResolver的getResources方法去拿到类的信息

		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let the bean factory post-processors apply to them!
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List priorityOrderedPostProcessors = new ArrayList<>();
		List orderedPostProcessorNames = new ArrayList<>();
		List nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		List orderedPostProcessors = new ArrayList<>();
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		List nonOrderedPostProcessors = new ArrayList<>();
		for (String postProcessorName : nonOrderedPostProcessorNames) {
			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

		// Clear cached merged bean definitions since the post-processors might have
		// modified the original metadata, e.g. replacing placeholders in values...
		beanFactory.clearMetadataCache();

主要去实例化和初始化实现了BeanFactoryPostProcessor的类和调用接口的方法。    先实例化接口的Ordered

具体实例化基于getBean 后面详细解释

6 registerBeanPostProcessors(beanFactory);

    实例化实现了BeanPostProcessors接口的类

这些暂时掠过
// 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();

7 finishBeanFactoryInitialization(beanFactory);   

  太多了，不写了，脑瓜子疼

https://blog.csdn.net/weixin_43901882/article/details/120069307