spring源码ConfigurationClassPostProcessor类的解析

我就是我 2023-10-02 20:25 27阅读 0赞

spring源码ConfigurationClassPostProcessor类的解析今天分享，此类很重要，里面会解析很多注解，比如@ComponentScans、@ComponentScan、@Component、@PropertySource、@Import等等。下面我们依次详细分析：

1、源码很熟悉的入口

@Test
        public void test3() {
            AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(ScanBean.class);
            SelectImportBean bean = applicationContext.getBean(SelectImportBean.class);
            System.out.println(bean);
        }

点击 AnnotationConfigApplicationContext 类进入有参构造函数

public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
    		this();//点击进入
    		register(componentClasses);
    		refresh();
    	}

点击this()进入无参构造函数

public AnnotationConfigApplicationContext() {
            //	private final AnnotatedBeanDefinitionReader reader;
    		this.reader = new AnnotatedBeanDefinitionReader(this);//核心代码，点击
    		this.scanner = new ClassPathBeanDefinitionScanner(this);
    	}

2、点击 AnnotatedBeanDefinitionReader 进入：

//用接口类接受，上游传的是实现类
       public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) {
    		this(registry, getOrCreateEnvironment(registry));//点击
    	}

点击进入：

public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
    		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
    		Assert.notNull(environment, "Environment must not be null");
    		this.registry = registry;
    		this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
            //核心代码，点击进入
    		AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
    	}

3、来到 AnnotationConfigUtils 类：

public static void registerAnnotationConfigProcessors(BeanDefinitionRegistry registry) {
    		registerAnnotationConfigProcessors(registry, null);//点击进入
    	}

来到：

public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
    			BeanDefinitionRegistry registry, @Nullable Object source) {
    
    		DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
    		if (beanFactory != null) {
    			if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
    				beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
    			}
    			if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
    				beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
    			}
    		}
    
    		Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);
            //把解析注解的多个.PostProcess类放到容器beanDefs 中，下游处理注解的类或参数时需要用到。
    
    		if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    			RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);//重要
    			def.setSource(source);
    //public static final String CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME =
    //	"org.springframework.context.annotation.internalConfigurationAnnotationProcessor";
    //此参数下游会通过SPI的思想取相应的实现类。
    			beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));//点击进入
    		}
    
    		if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    			RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
    			def.setSource(source);
    			beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
    		}
    
    		// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
    		if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    			RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
    			def.setSource(source);
    			beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
    		}
    
    		// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
    		if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
    			RootBeanDefinition def = new RootBeanDefinition();
    			try {
    				def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
    						AnnotationConfigUtils.class.getClassLoader()));
    			}
    			catch (ClassNotFoundException ex) {
    				throw new IllegalStateException(
    						"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
    			}
    			def.setSource(source);
    			beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
    		}
    
    		if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
    			RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
    			def.setSource(source);
    			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
    		}
    
    		if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
    			RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
    			def.setSource(source);
    			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
    		}
    
    		return beanDefs;
    	}

点击registerPostProcessor 方法：

private static BeanDefinitionHolder registerPostProcessor(
    			BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) {
    
    		definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
    		registry.registerBeanDefinition(beanName, definition);
    		return new BeanDefinitionHolder(definition, beanName);//点击进入
    	}

来到BeanDefinitionHolder 类：

public BeanDefinitionHolder(BeanDefinition beanDefinition, String beanName) {
    		this(beanDefinition, beanName, null);//点击进入
    	}

来到：

public BeanDefinitionHolder(BeanDefinition beanDefinition, String beanName, @Nullable String[] aliases) {
    		Assert.notNull(beanDefinition, "BeanDefinition must not be null");
    		Assert.notNull(beanName, "Bean name must not be null");
    		this.beanDefinition = beanDefinition;
    		this.beanName = beanName;//重点参数，后期下游业务会替换成标准的名称
    		this.aliases = aliases;
    	}

第一阶段5个特殊的.postProcessor 初始化到beanDefinition对象里，如下图：

![d5b2d70ac7ed4b8a8d28c6ea9559bcd2.png][]

第二阶段开始，入口如下：

/*
    				 * BeanDefinitionRegistryPostProcessor
    				 * BeanFactoryPostProcessor
    				 * 完成对这两个接口的调用等等
    				 * */
    				invokeBeanFactoryPostProcessors(beanFactory);

4、点击进入：

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {//点击进入
    		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
    
    		// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
    		// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
    		if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
    			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
    			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
    		}
    	}

来到：

![aa474ee5a82545e4a9551d30bb7df0bd.png][]

点击 invokeBeanDefinitionRegistryPostProcessors 进入：

private static void invokeBeanDefinitionRegistryPostProcessors(
    			Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
    
    		for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
    			postProcessor.postProcessBeanDefinitionRegistry(registry);//点击
    		}
    	}

进入

![b613e14a3808481393f9ac6089e23973.png][]

5、循环来到 ConfigurationClassPostProcessor类：

@Override
    	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    		int registryId = System.identityHashCode(registry);
    		if (this.registriesPostProcessed.contains(registryId)) {
    			throw new IllegalStateException(
    					"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
    		}
    		if (this.factoriesPostProcessed.contains(registryId)) {
    			throw new IllegalStateException(
    					"postProcessBeanFactory already called on this post-processor against " + registry);
    		}
    		this.registriesPostProcessed.add(registryId);
    
    		//核心逻辑，重点看，点击进入
    		processConfigBeanDefinitions(registry);
    	}

6、点击 processConfigBeanDefinitions 来到

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
    		List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
    		//获取所有的beanNames
    		String[] candidateNames = registry.getBeanDefinitionNames();
    
    		for (String beanName : candidateNames) {
    			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
    			//如果有该标识就不再处理
    			if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
    				if (logger.isDebugEnabled()) {
    					logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
    				}
    			}
    			//判断是否是候选的需要处理的BeanDefinition，如果是则放入容器configCandidates
    			else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
    				configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
    			}
    		}
    
    		// Return immediately if no @Configuration classes were found
    		//如果容器为空，则直接返回
    		if (configCandidates.isEmpty()) {
    			return;
    		}
    
    		// Sort by previously determined @Order value, if applicable
    		//对需要处理的所有beanDefinition排序
    		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();
    		}
    
    		//候选BeanDefinition的解析器
    		// 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 {
    			//解析核心流程，重点看，点击进入
    			//其实就是把类上面的特殊注解解析出来最终封装成beanDefinition
    			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());
    			}
    			//@Bean @Import 内部类 @ImportedResource ImportBeanDefinitionRegistrar具体处理逻辑
    //private ConfigurationClassBeanDefinitionReader reader;
    			this.reader.loadBeanDefinitions(configClasses);
    			//已经解析完成了的类
    			alreadyParsed.addAll(configClasses);
    
    			candidates.clear();
    			//比较差异又走一遍解析流程
    			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();
    		}
    	}

点击 ConfigurationClassUtils.checkConfigurationClassCandidate 验证方法，来到ConfigurationClassUtils 类：

public static boolean checkConfigurationClassCandidate(
    			BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
    
    		String className = beanDef.getBeanClassName();
    		if (className == null || beanDef.getFactoryMethodName() != null) {
    			return false;
    		}
    
    		AnnotationMetadata metadata;
    		//如果是扫描注解产生的BeanDefinition
    		if (beanDef instanceof AnnotatedBeanDefinition &&
    				className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
    			// Can reuse the pre-parsed metadata from the given BeanDefinition...
    			metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();
    		}
    		//非扫描注解产生的beanDefinition
    		else if (beanDef instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) beanDef).hasBeanClass()) {
    			// Check already loaded Class if present...
    			// since we possibly can't even load the class file for this Class.
    			Class<?> beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();
    			if (BeanFactoryPostProcessor.class.isAssignableFrom(beanClass) ||
    					BeanPostProcessor.class.isAssignableFrom(beanClass) ||
    					AopInfrastructureBean.class.isAssignableFrom(beanClass) ||
    					EventListenerFactory.class.isAssignableFrom(beanClass)) {
    				return false;
    			}
    			metadata = AnnotationMetadata.introspect(beanClass);
    		}
    		else {
    			try {
    				MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(className);
    				metadata = metadataReader.getAnnotationMetadata();
    			}
    			catch (IOException ex) {
    				if (logger.isDebugEnabled()) {
    					logger.debug("Could not find class file for introspecting configuration annotations: " +
    							className, ex);
    				}
    				return false;
    			}
    		}
    
    		//从metadata中获取Configuration注解
    		Map<String, Object> config = metadata.getAnnotationAttributes(Configuration.class.getName());
    		//如果有Configuration注解，就是完全匹配标识
    		if (config != null && !Boolean.FALSE.equals(config.get("proxyBeanMethods"))) {
    			beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
    		}
    		//如果是有Component ComponentScan Import ImportResource或者方法上面有@Bean，就是lite匹配，点击进入
    		else if (config != null || isConfigurationCandidate(metadata)) {
    			beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
    		}
    		else {
    			return false;
    		}
    
    		//获取@Order注解值
    		// It's a full or lite configuration candidate... Let's determine the order value, if any.
    		Integer order = getOrder(metadata);
    		if (order != null) {
    			beanDef.setAttribute(ORDER_ATTRIBUTE, order);
    		}
    
    		return true;
    	}

点击isConfigurationCandidate(metadata)方法

public static boolean isConfigurationCandidate(AnnotationMetadata metadata) {
    		// Do not consider an interface or an annotation...
    		if (metadata.isInterface()) {
    			return false;
    		}
    
    		// Any of the typical annotations found?
            // candidateIndicators 是注解的集合
    		for (String indicator : candidateIndicators) {
    			if (metadata.isAnnotated(indicator)) {
    				return true;
    			}
    		}
    
    		// Finally, let's look for @Bean methods...
    		try {
    			return metadata.hasAnnotatedMethods(Bean.class.getName());
    		}
    		catch (Throwable ex) {
    			if (logger.isDebugEnabled()) {
    				logger.debug("Failed to introspect @Bean methods on class [" + metadata.getClassName() + "]: " + ex);
    			}
    			return false;
    		}
    	}

注解集合在静态代码块里，初始化对象时就加载好了

private static final Set<String> candidateIndicators = new HashSet<>(8);
    
    	static {
    		candidateIndicators.add(Component.class.getName());
    		candidateIndicators.add(ComponentScan.class.getName());
    		candidateIndicators.add(Import.class.getName());
    		candidateIndicators.add(ImportResource.class.getName());
    	}

进入下游的业务

7、点击parser.parse(candidates); 来到 ConfigurationClassParser 类

public void parse(Set<BeanDefinitionHolder> configCandidates) {
    		for (BeanDefinitionHolder holder : configCandidates) {
    			BeanDefinition bd = holder.getBeanDefinition();
    			try {
    				//扫描注解得到的BeanDefinition，点击进入
    				if (bd instanceof AnnotatedBeanDefinition) {
    					parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
    				}
    				//非扫描注解得到的BeanDefinition，进入
    				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);
    			}
    		}
    		//这行代码不能忽视,点击进入
    		this.deferredImportSelectorHandler.process();
    	}

点击parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());

protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
    		//把metadata对象和beanName封装成ConfigurationClass对象
    		processConfigurationClass(new ConfigurationClass(metadata, beanName), DEFAULT_EXCLUSION_FILTER);
    	}

点击

protected void processConfigurationClass(ConfigurationClass configClass, Predicate<String> filter) throws IOException {
    		//对@Condition注解的支持，过滤掉不需要实例化的类
    		if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
    			return;
    		}
    
    		ConfigurationClass existingClass = this.configurationClasses.get(configClass);
    		if (existingClass != null) {
    			if (configClass.isImported()) {
    				if (existingClass.isImported()) {
    					existingClass.mergeImportedBy(configClass);
    				}
    				// Otherwise ignore new imported config class; existing non-imported class overrides it.
    				return;
    			}
    			else {
    				// Explicit bean definition found, probably replacing an import.
    				// Let's remove the old one and go with the new one.
    				this.configurationClasses.remove(configClass);
    				this.knownSuperclasses.values().removeIf(configClass::equals);
    			}
    		}
    
    		//这个对象理解为跟类或者接口对应，然后把metadata对象包装进去了
    		// Recursively process the configuration class and its superclass hierarchy.
    		SourceClass sourceClass = asSourceClass(configClass, filter);
    		do {
    			//核心代码，认真读，点击进入
    			sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
    		}
    		while (sourceClass != null);
    
    		this.configurationClasses.put(configClass, configClass);
    	}

点击doProcessConfigurationClass 方法

@Nullable
    	protected final SourceClass doProcessConfigurationClass(
    			ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
    			throws IOException {
    
    		//判断类上面是否有Component注解
    		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
    			// Recursively process any member (nested) classes first
    			//递归处理有@Component注解的内部类，点击
    			processMemberClasses(configClass, sourceClass, filter);
    		}
    
    		// Process any @PropertySource annotations
    		//处理PropertySources和 PropertySource注解
    		for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
    				sourceClass.getMetadata(), PropertySources.class,
    				org.springframework.context.annotation.PropertySource.class)) {
    			if (this.environment instanceof ConfigurableEnvironment) {
    				//核心逻辑
    				processPropertySource(propertySource);
    			}
    			else {
    				logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
    						"]. Reason: Environment must implement ConfigurableEnvironment");
    			}
    		}
    
    		// Process any @ComponentScan annotations
    		//处理ComponentScans和ComponentScan注解
    		Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
    				sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
    		//是否需要跳过
    		if (!componentScans.isEmpty() &&
    				!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
    			for (AnnotationAttributes componentScan : componentScans) {
    				// The config class is annotated with @ComponentScan -> perform the scan immediately
    				//这个parse里面的逻辑，基本上跟我们<component-scan>自定义标签解析的逻辑差不多
    				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
    				//这里又去递归，扫描到@Component生成beanDefinition后，又递归去校验类上面是否有特殊注解
    				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
    					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
    					if (bdCand == null) {
    						bdCand = holder.getBeanDefinition();
    					}
    					//判断是否是候选的BeanDefinition，如果是又parse
    					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
    						parse(bdCand.getBeanClassName(), holder.getBeanName());
    					}
    				}
    			}
    		}
    
    		//处理@Import注解 getImports(sourceClass) 获取类上面的@Import注解并封装成SourceClass
    		// Process any @Import annotations
    		processImports(configClass, sourceClass, getImports(sourceClass), filter, true);
    
    		//处理@ImportResource注解 ，没啥用，加载xml配置文件
    		// Process any @ImportResource annotations
    		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);
    				//建立xml文件和reader的映射关系
    				configClass.addImportedResource(resolvedResource, readerClass);
    			}
    		}
    
    		//处理@Bean注解，重点
    		// Process individual @Bean methods
    		//收集有@bean 注解的方法
    		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
    		for (MethodMetadata methodMetadata : beanMethods) {
    			//加入到ConfigurationClass中
    			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
    		}
    
    		//处理接口里面方法有@Bean注解的，逻辑差不多
    		// 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;
    	}

点击processMemberClasses(configClass, sourceClass, filter);

private void processMemberClasses(ConfigurationClass configClass, SourceClass sourceClass,
    			Predicate<String> filter) throws IOException {
    
    		//获取该类的内部类并又包装成sourceClass对象
    		Collection<SourceClass> memberClasses = sourceClass.getMemberClasses();
    		if (!memberClasses.isEmpty()) {
    			List<SourceClass> candidates = new ArrayList<>(memberClasses.size());
    			for (SourceClass memberClass : memberClasses) {
    				//如果类是候选的
    				if (ConfigurationClassUtils.isConfigurationCandidate(memberClass.getMetadata()) &&
    						!memberClass.getMetadata().getClassName().equals(configClass.getMetadata().getClassName())) {
    					candidates.add(memberClass);
    				}
    			}
    			//排序
    			OrderComparator.sort(candidates);
    			//循环去处理每一个内部类
    			for (SourceClass candidate : candidates) {
    				if (this.importStack.contains(configClass)) {
    					this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
    				}
    				else {
    					this.importStack.push(configClass);
    					try {
    						//candidate 子  configClass 父，candidate 是 configClass的内部类
    						processConfigurationClass(candidate.asConfigClass(configClass), filter);
    					}
    					finally {
    						this.importStack.pop();
    					}
    				}
    			}
    		}
    	}

返回 点击 processPropertySource(propertySource);

private void processPropertySource(AnnotationAttributes propertySource) throws IOException {
    		String name = propertySource.getString("name");
    		if (!StringUtils.hasLength(name)) {
    			name = null;
    		}
    		String encoding = propertySource.getString("encoding");
    		if (!StringUtils.hasLength(encoding)) {
    			encoding = null;
    		}
    		//获取配置文件路径
    		String[] locations = propertySource.getStringArray("value");
    		Assert.isTrue(locations.length > 0, "At least one @PropertySource(value) location is required");
    		boolean ignoreResourceNotFound = propertySource.getBoolean("ignoreResourceNotFound");
    
    		Class<? extends PropertySourceFactory> factoryClass = propertySource.getClass("factory");
    		PropertySourceFactory factory = (factoryClass == PropertySourceFactory.class ?
    				DEFAULT_PROPERTY_SOURCE_FACTORY : BeanUtils.instantiateClass(factoryClass));
    
    		for (String location : locations) {
    			try {
    				//替换占位符
    				String resolvedLocation = this.environment.resolveRequiredPlaceholders(location);
    				//流的方式加载配置文件并封装成Resource对象
    				Resource resource = this.resourceLoader.getResource(resolvedLocation);
    				//加载Resource中的配置属性封装成Properties对象中，并创建PropertySource对象加入到Environment对象中
    				addPropertySource(factory.createPropertySource(name, new EncodedResource(resource, encoding)));
    			}
    			catch (IllegalArgumentException | FileNotFoundException | UnknownHostException ex) {
    				// Placeholders not resolvable or resource not found when trying to open it
    				if (ignoreResourceNotFound) {
    					if (logger.isInfoEnabled()) {
    						logger.info("Properties location [" + location + "] not resolvable: " + ex.getMessage());
    					}
    				}
    				else {
    					throw ex;
    				}
    			}
    		}
    	}

点击addPropertySource

private void addPropertySource(PropertySource<?> propertySource) {
    		String name = propertySource.getName();
    		//获取Environment对象中的MutablePropertySources
    		MutablePropertySources propertySources = ((ConfigurableEnvironment) this.environment).getPropertySources();
    
    		//如果已经存在了该配置文件的PropertySource则合并久的
    		if (this.propertySourceNames.contains(name)) {
    			// We've already added a version, we need to extend it
    			PropertySource<?> existing = propertySources.get(name);
    			if (existing != null) {
    				PropertySource<?> newSource = (propertySource instanceof ResourcePropertySource ?
    						((ResourcePropertySource) propertySource).withResourceName() : propertySource);
    				//合并二次后的类型
    				if (existing instanceof CompositePropertySource) {
    					((CompositePropertySource) existing).addFirstPropertySource(newSource);
    				}
    				else {
    					if (existing instanceof ResourcePropertySource) {
    						existing = ((ResourcePropertySource) existing).withResourceName();
    					}
    					//其实就是CompositePropertySource里面有一个Set，Set里面装了新和旧的PropertySource对象
    					CompositePropertySource composite = new CompositePropertySource(name);
    					composite.addPropertySource(newSource);
    					composite.addPropertySource(existing);
    					propertySources.replace(name, composite);
    				}
    				return;
    			}
    		}
    
    		if (this.propertySourceNames.isEmpty()) {
    			propertySources.addLast(propertySource);
    		}
    		else {
    			//用于计算插入的位置index
    			String firstProcessed = this.propertySourceNames.get(this.propertySourceNames.size() - 1);
    			//吧propertySource对象存入MutablePropertySources的list中
    			propertySources.addBefore(firstProcessed, propertySource);
    		}
    		this.propertySourceNames.add(name);
    	}

8、返回调用 processImports(configClass, sourceClass, getImports(sourceClass), filter, true);

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
    			Collection<SourceClass> importCandidates, Predicate<String> exclusionFilter,
    			boolean checkForCircularImports) {
    
    		//如果没有@Import注解直接返回，不处理
    		if (importCandidates.isEmpty()) {
    			return;
    		}
    
    		if (checkForCircularImports && isChainedImportOnStack(configClass)) {
    			this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
    		}
    		else {
    			this.importStack.push(configClass);
    			try {
    				//循环类上面的每一个@Import
    				for (SourceClass candidate : importCandidates) {
    					//如果Import进来的是一个ImportSelector类型
    					if (candidate.isAssignable(ImportSelector.class)) {
    						// Candidate class is an ImportSelector -> delegate to it to determine imports
    						Class<?> candidateClass = candidate.loadClass();
    						//反射实例化
    						ImportSelector selector = ParserStrategyUtils.instantiateClass(candidateClass, ImportSelector.class,
    								this.environment, this.resourceLoader, this.registry);
    						Predicate<String> selectorFilter = selector.getExclusionFilter();
    						if (selectorFilter != null) {
    							exclusionFilter = exclusionFilter.or(selectorFilter);
    						}
    						//如果是一个DeferredImportSelector类型
    						if (selector instanceof DeferredImportSelector) {
    							//比较复杂，springboot中自动配置用到了
    							this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
    						}
    						else {
    							//在这里调用selectImports方法，返回所有的需要import到spring容器的beanName
    							String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
    							Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames, exclusionFilter);
    							//递归处理，有可能import进来的类又有@Import注解
    							processImports(configClass, currentSourceClass, importSourceClasses, exclusionFilter, false);
    						}
    					}
    					//如果Import进来的是一个ImportBeanDefinitionRegistrar类型
    					else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
    						// Candidate class is an ImportBeanDefinitionRegistrar ->
    						// delegate to it to register additional bean definitions
    						Class<?> candidateClass = candidate.loadClass();
    						//反射实例化
    						ImportBeanDefinitionRegistrar registrar =
    								ParserStrategyUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class,
    										this.environment, this.resourceLoader, this.registry);
    						//加入到importBeanDefinitionRegistrars容器中，这里还没有调用registerBeanDefinitions
    						configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
    					}
    					else {
    						// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
    						// process it as an @Configuration class
    						this.importStack.registerImport(
    								currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
    						//如果都不是，则走这里
    						processConfigurationClass(candidate.asConfigClass(configClass), exclusionFilter);
    					}
    				}
    			}
    			catch (BeanDefinitionStoreException ex) {
    				throw ex;
    			}
    			catch (Throwable ex) {
    				throw new BeanDefinitionStoreException(
    						"Failed to process import candidates for configuration class [" +
    						configClass.getMetadata().getClassName() + "]", ex);
    			}
    			finally {
    				this.importStack.pop();
    			}
    		}
    	}

点击 getImports(sourceClass)方法

private Set<SourceClass> getImports(SourceClass sourceClass) throws IOException {
    		Set<SourceClass> imports = new LinkedHashSet<>();
    		Set<SourceClass> visited = new LinkedHashSet<>();
    		collectImports(sourceClass, imports, visited);//点击进入
    		return imports;
    	}

来到 collectImports(sourceClass, imports, visited);方法

private void collectImports(SourceClass sourceClass, Set<SourceClass> imports, Set<SourceClass> visited)
    			throws IOException {
    
    		if (visited.add(sourceClass)) {
    			for (SourceClass annotation : sourceClass.getAnnotations()) {
    				String annName = annotation.getMetadata().getClassName();
    				if (!annName.equals(Import.class.getName())) {
    					collectImports(annotation, imports, visited);//判断是否有Import注解
    				}
    			}
    			imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), "value"));
    		}
    	}

9、返回 调用 processInterfaces(configClass, sourceClass);

private void processInterfaces(ConfigurationClass configClass, SourceClass sourceClass) throws IOException {
    		for (SourceClass ifc : sourceClass.getInterfaces()) {
    			Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(ifc);
    			for (MethodMetadata methodMetadata : beanMethods) {
    				if (!methodMetadata.isAbstract()) {
    					// A default method or other concrete method on a Java 8+ interface...
    					configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
    				}
    			}
    			processInterfaces(configClass, ifc);//递归调用
    		}
    	}

10、返回processConfigBeanDefinitions 方法点击 this.reader.loadBeanDefinitions(configClasses);

进入 ConfigurationClassBeanDefinitionReader 类：

public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
    		TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
    		for (ConfigurationClass configClass : configurationModel) {
    			loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);//点击进入
    		}
    	}

来到：

private void loadBeanDefinitionsForConfigurationClass(
    			ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
    
    		//是否要跳过
    		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;
    		}
    
    		//@Import进来的类，和内部类走这里变成BeanDefinition
    		if (configClass.isImported()) {
    			registerBeanDefinitionForImportedConfigurationClass(configClass);
    		}
    		//@Bean注解的方法变成BeanDefinition
    		for (BeanMethod beanMethod : configClass.getBeanMethods()) {
    			loadBeanDefinitionsForBeanMethod(beanMethod);
    		}
    
    		//走xml解析流程，点击进入
    		loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
    		//调用ImportBeanDefinitionRegistrar的方法，点击进入
    		loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
    	}

点击loadBeanDefinitionsFromImportedResources 方法

private void loadBeanDefinitionsFromImportedResources(
    			Map<String, Class<? extends BeanDefinitionReader>> importedResources) {
    
    		Map<Class<?>, BeanDefinitionReader> readerInstanceCache = new HashMap<>();
    
    		importedResources.forEach((resource, readerClass) -> {
    			// Default reader selection necessary?
    			if (BeanDefinitionReader.class == readerClass) {
    				if (StringUtils.endsWithIgnoreCase(resource, ".groovy")) {
    					// When clearly asking for Groovy, that's what they'll get...
    					readerClass = GroovyBeanDefinitionReader.class;
    				}
    				else {
    					// Primarily ".xml" files but for any other extension as well
    					readerClass = XmlBeanDefinitionReader.class;
    				}
    			}
    
    			BeanDefinitionReader reader = readerInstanceCache.get(readerClass);
    			if (reader == null) {
    				try {
    					// Instantiate the specified BeanDefinitionReader
    					reader = readerClass.getConstructor(BeanDefinitionRegistry.class).newInstance(this.registry);
    					// Delegate the current ResourceLoader to it if possible
    					if (reader instanceof AbstractBeanDefinitionReader) {
    						AbstractBeanDefinitionReader abdr = ((AbstractBeanDefinitionReader) reader);
    						abdr.setResourceLoader(this.resourceLoader);
    						abdr.setEnvironment(this.environment);
    					}
    					readerInstanceCache.put(readerClass, reader);
    				}
    				catch (Throwable ex) {
    					throw new IllegalStateException(
    							"Could not instantiate BeanDefinitionReader class [" + readerClass.getName() + "]");
    				}
    			}
    
    			//这个逻辑，xml解析时已经讲过，点击大概看看
    			// TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
    			reader.loadBeanDefinitions(resource);
    		});
    	}

如图：

![2d1cbb012db148de87c5294c4b7663ac.png][] 此时你就恍然大悟了吧，这就是我们最初分析xml文件的过程。

点击 loadBeanDefinitionsFromRegistrars 方法

private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {
    		registrars.forEach((registrar, metadata) ->
    				registrar.registerBeanDefinitions(metadata, this.registry, this.importBeanNameGenerator));//点击
    	}

点击来到 ImportBeanDefinitionRegistrar 接口

default void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry,
    			BeanNameGenerator importBeanNameGenerator) {
    
    		registerBeanDefinitions(importingClassMetadata, registry);//点击
    	}

点击：来到业务实现类

![5bc55b68a5c644faa6d824da4a581af7.png][]

进入看看自定义业务：

import com.enjoy.jack.bean.BeanDefinitionBean;
    import org.springframework.beans.MutablePropertyValues;
    import org.springframework.beans.factory.support.BeanDefinitionRegistry;
    import org.springframework.beans.factory.support.GenericBeanDefinition;
    import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
    import org.springframework.core.type.AnnotationMetadata;
    
    /**
     * @Classname JamesImportBeanDefinitionRegistrar
     * @Author Nandao
     */
    public class JamesImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
        @Override
        public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
            //自己创建beanDefinition对象，然后注册到BeanDefinitionRegistry中
            GenericBeanDefinition genericBeanDefinition = new GenericBeanDefinition();
            genericBeanDefinition.setBeanClass(BeanDefinitionBean.class);
            MutablePropertyValues propertyValues = genericBeanDefinition.getPropertyValues();
            propertyValues.add("name","Nandao");
            registry.registerBeanDefinition("beanDefinitionBean",genericBeanDefinition);
        }
    }

到此、spring源码ConfigurationClassPostProcessor类的解析分析完毕，下篇我们分析其相关注解的使用，敬请期待！

[d5b2d70ac7ed4b8a8d28c6ea9559bcd2.png]: https://img-blog.csdnimg.cn/d5b2d70ac7ed4b8a8d28c6ea9559bcd2.png
[aa474ee5a82545e4a9551d30bb7df0bd.png]: https://img-blog.csdnimg.cn/aa474ee5a82545e4a9551d30bb7df0bd.png
[b613e14a3808481393f9ac6089e23973.png]: https://img-blog.csdnimg.cn/b613e14a3808481393f9ac6089e23973.png
[2d1cbb012db148de87c5294c4b7663ac.png]: https://img-blog.csdnimg.cn/2d1cbb012db148de87c5294c4b7663ac.png
[5bc55b68a5c644faa6d824da4a581af7.png]: https://img-blog.csdnimg.cn/5bc55b68a5c644faa6d824da4a581af7.png