代码使用springboot测试

1.ConfigurationClassPostProcessor

构造context时会创建reader。

构造reader时会创建processor。
最关键是第一个，类型是ConfigurationClassPostProcessor。

AbstractApplicationContext类的refresh方法的invokeBeanFactoryPostProcessors方法会调用PostProcessorRegistrationDelegate类的invokeBeanFactoryPostProcessors方法

这个方法会从beanDefinitions中拿到ConfigurationClassPostProcessor，然后进行实例化，然后执行它，执行它的目的就是注册其他的beanDefinition，例如有component注解的类

	public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

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

		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {
					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.
			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

			// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
			//关键1 这里会拿到而且只能拿到上面标题1的ConfigurationClassPostProcessor
			//为什么能拿到？ 因为ConfigurationClassPostProcessor实现了BeanDefinitionRegistryPostProcessor接口
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			//遍历 其实就一个		
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					//通过名字实例化ConfigurationClassPostProcessor，添加到currentRegistryProcessors这个list中
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			//关键方法 执行上面实例化的ConfigurationClassPostProcessor
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
			//关键2 和关键1相同的步骤 关键1中已经导入了一部分beanDefinition 所以这里再重新获取一次
			//可能会获取到别的实现了BeanDefinitionRegistryPostProcessor接口的类
			//这里如果用了mybatis 则会获取到MapperScannerConfigurer，因为它实现了BeanDefinitionRegistryPostProcessor接口
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				//这里判断关键1中已经获取的就不要了 还有一个条件是ordered MapperScannerConfigurer不会通过判断 所以继续向下执行
				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;
				//关键3 这里再获取一次 还是关键2中获取的那两个
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					//这里只会排除关键1中获取的ConfigurationClassPostProcessor
					//少了ordered的判断条件 所以MapperScannerConfigurer会通过判断
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				//执行MapperScannerConfigurer 获取mapper接口的beanDefinition
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
			}

			// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// Invoke factory processors registered with the context instance.
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		// 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<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> 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<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		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();
	}

1.1.关键1的invokeBeanDefinitionRegistryPostProcessors方法

上面代码中关键1的invokeBeanDefinitionRegistryPostProcessors方法最终会调用ConfigurationClassPostProcessor类的processConfigBeanDefinitions方法。
这个方法会获取到启动类，然后根据启动类的@SpringBootApplication注解下的@ComponentScan注解去注册beanDefinition （ConfigurationClassParser 的parse方法）

	public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
		//获取到所有的beanDefinition，springboot项目这里能获取到启动类和标题1获取的几个processor，启动类的获取是在run方法的prepareContext方法的结尾处，启动类调用run方法会传进去启动类
		String[] candidateNames = registry.getBeanDefinitionNames();
		//遍历拿到启动类
		for (String beanName : candidateNames) {
			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
			if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
				if (logger.isDebugEnabled()) {
					logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
				}
			}
			//启动类会进这个判断
			else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
				configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
			}
		}

		// Return immediately if no @Configuration classes were found
		if (configCandidates.isEmpty()) {
			return;
		}

		// Sort by previously determined @Order value, if applicable
		configCandidates.sort((bd1, bd2) -> {
			int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
			int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
			return Integer.compare(i1, i2);
		});

		// Detect any custom bean name generation strategy supplied through the enclosing application context
		SingletonBeanRegistry sbr = null;
		if (registry instanceof SingletonBeanRegistry) {
			sbr = (SingletonBeanRegistry) registry;
			if (!this.localBeanNameGeneratorSet) {
				BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(
						AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR);
				if (generator != null) {
					this.componentScanBeanNameGenerator = generator;
					this.importBeanNameGenerator = generator;
				}
			}
		}

		if (this.environment == null) {
			this.environment = new StandardEnvironment();
		}

		// Parse each @Configuration class
		ConfigurationClassParser parser = new ConfigurationClassParser(
				this.metadataReaderFactory, this.problemReporter, this.environment,
				this.resourceLoader, this.componentScanBeanNameGenerator, registry);

		Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
		Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
		do {
			//ConfigurationClassParser 的parse方法 传入启动类
			//这个方法解析ComponentScan注解 Component注解
			//关键1
			parser.parse(candidates);
			parser.validate();

			Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
			configClasses.removeAll(alreadyParsed);

			// Read the model and create bean definitions based on its content
			if (this.reader == null) {
				this.reader = new ConfigurationClassBeanDefinitionReader(
						registry, this.sourceExtractor, this.resourceLoader, this.environment,
						this.importBeanNameGenerator, parser.getImportRegistry());
			}
			this.reader.loadBeanDefinitions(configClasses);
			alreadyParsed.addAll(configClasses);

			candidates.clear();
			if (registry.getBeanDefinitionCount() > candidateNames.length) {
				String[] newCandidateNames = registry.getBeanDefinitionNames();
				Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
				Set<String> alreadyParsedClasses = new HashSet<>();
				for (ConfigurationClass configurationClass : alreadyParsed) {
					alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
				}
				for (String candidateName : newCandidateNames) {
					if (!oldCandidateNames.contains(candidateName)) {
						BeanDefinition bd = registry.getBeanDefinition(candidateName);
						if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
								!alreadyParsedClasses.contains(bd.getBeanClassName())) {
							candidates.add(new BeanDefinitionHolder(bd, candidateName));
						}
					}
				}
				candidateNames = newCandidateNames;
			}
		}
		while (!candidates.isEmpty());

		// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
		if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
			sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
		}

		if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
			// Clear cache in externally provided MetadataReaderFactory; this is a no-op
			// for a shared cache since it'll be cleared by the ApplicationContext.
			((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
		}
	}

1.1.1 ConfigurationClassParser 的parse方法

	public void parse(Set<BeanDefinitionHolder> configCandidates) {
		for (BeanDefinitionHolder holder : configCandidates) {
			BeanDefinition bd = holder.getBeanDefinition();
			try {
				//关键1 启动类会进入这个判断
				if (bd instanceof AnnotatedBeanDefinition) {
					parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
				}
				else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
					parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
				}
				else {
					parse(bd.getBeanClassName(), holder.getBeanName());
				}
			}
			catch (BeanDefinitionStoreException ex) {
				throw ex;
			}
			catch (Throwable ex) {
				throw new BeanDefinitionStoreException(
						"Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
			}
		}
		//关键2 处理autoconfig的类（META-INF下spring.factories文件中） 这个会有很多 而且不是直接变成beandefinition 而是存在ConfigurationClassParser类的configurationClasses属性中
		this.deferredImportSelectorHandler.process();
	}

关键1.最终会调用ConfigurationClassParser类的doProcessConfigurationClass方法
就会把controller service component configuration注解的类加到beandefinition中。同时还会处理传入的参数（也就是启动类）的内部类@bean @import注解

	protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
			throws IOException {
		//处理Component注解的类的内部的bean
		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
			// Recursively process any member (nested) classes first
			processMemberClasses(configClass, sourceClass);
		}

		// Process any @PropertySource annotations
		for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), PropertySources.class,
				org.springframework.context.annotation.PropertySource.class)) {
			if (this.environment instanceof ConfigurableEnvironment) {
				processPropertySource(propertySource);
			}
			else {
				logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
						"]. Reason: Environment must implement ConfigurableEnvironment");
			}
		}

		// Process any @ComponentScan annotations
		//关键 获取所有的componentScan注解 启动类刚好有一个这个注解
		Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
		if (!componentScans.isEmpty() &&
				!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
				//遍历 其实就一个
			for (AnnotationAttributes componentScan : componentScans) {
				// The config class is annotated with @ComponentScan -> perform the scan immediately
				//调用componentScanParser.parse处理componentScan注解
				Set<BeanDefinitionHolder> scannedBeanDefinitions =
						this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
				// Check the set of scanned definitions for any further config classes and parse recursively if needed
				//scannedBeanDefinitions里边有了controller service component configuration注解的类
				//这里遍历是递归调用parse方法 应该是处理内部类的 暂不处理
				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
					if (bdCand == null) {
						bdCand = holder.getBeanDefinition();
					}
					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
						parse(bdCand.getBeanClassName(), holder.getBeanName());
					}
				}
			}
		}

		// Process any @Import annotations
		//处理启动类的@Import注解
		processImports(configClass, sourceClass, getImports(sourceClass), true);

		// Process any @ImportResource annotations
		//处理启动类的@ImportResource注解
		AnnotationAttributes importResource =
				AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
		if (importResource != null) {
			String[] resources = importResource.getStringArray("locations");
			Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
			for (String resource : resources) {
				String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
				configClass.addImportedResource(resolvedResource, readerClass);
			}
		}

		// Process individual @Bean methods
		//处理启动类的@Bean注解
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}

		// Process default methods on interfaces
		processInterfaces(configClass, sourceClass);

		// Process superclass, if any
		if (sourceClass.getMetadata().hasSuperClass()) {
			String superclass = sourceClass.getMetadata().getSuperClassName();
			if (superclass != null && !superclass.startsWith("java") &&
					!this.knownSuperclasses.containsKey(superclass)) {
				this.knownSuperclasses.put(superclass, configClass);
				// Superclass found, return its annotation metadata and recurse
				return sourceClass.getSuperClass();
			}
		}

		// No superclass -> processing is complete
		return null;
	}

2.deferredImportSelectorHandler.process()方法
目的是获取自动配置类（META-INF下spring.factories文件中）存在ConfigurationClassParser类的configurationClasses属性中。

1.1.2 this.reader.loadBeanDefinitions(configClasses)方法

ConfigurationClassBeanDefinitionReader类的loadBeanDefinitions方法
传进来的就是ConfigurationClassParser类的configurationClasses属性。一个set集合，保存所有配置类。
遍历处理配置类中引入的bean

org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader#loadBeanDefinitionsForConfigurationClass方法

private void loadBeanDefinitionsForConfigurationClass(
		ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {

	if (trackedConditionEvaluator.shouldSkip(configClass)) {
		String beanName = configClass.getBeanName();
		if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
			this.registry.removeBeanDefinition(beanName);
		}
		this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
		return;
	}
	//处理当前遍历的类 看当前配置类的importedBy属性不为空就添加到beandifinition
	if (configClass.isImported()) {
		registerBeanDefinitionForImportedConfigurationClass(configClass);
	}
	//处理当前遍历的类中 @bean注解引入的类 添加到beandifinition
	for (BeanMethod beanMethod : configClass.getBeanMethods()) {
		loadBeanDefinitionsForBeanMethod(beanMethod);
	}
	
	loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
	//处理实现beanDefinitionRegistrars接口的类
	loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}

经过这两个步骤 所有需要导入的bean（configuration controller service component ）以及自动配置类和自动配置类中@bean的类都变成了beandefinition
过程：
先注册ConfigurationClassPostProcessor成为beandefinition，然后进行实例化，然后执行它，然后会获取到启动类，也就是componentScan注解，然后调用ConfigurationClassParser 的parse方法，这个方法有两个作用，1是调用componentScanParser.parse方法，完成componentScan配置的包下的@Component（controller service Configuration）注解的类的注册，2是调用deferredImportSelectorHandler.process()方法获取自动配置类及内部的@bean导入的类放在ConfigurationClassParser类的configurationClasses属性中。然后在ConfigurationClassBeanDefinitionReader类的loadBeanDefinitions方法中完成注册。