Spring BeanDefinition的解析过程源码分析(下)

本文主要是介绍Spring BeanDefinition的解析过程源码分析(下)，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

前言

本文主要接上文Spring BeanDefinition的解析过程源码分析(上)
上文讲到准备调用refresh()，本文还是不会对refresh()方法中所有方法进行分析，还是围绕BeanDefinition的解析来分析，本文篇幅可能过长！

进入refresh()方法

@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			prepareRefresh();

			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			prepareBeanFactory(beanFactory);

			try {
				postProcessBeanFactory(beanFactory);

				invokeBeanFactoryPostProcessors(beanFactory);

				......
			}

		}
	}

关键方法在于invokeBeanFactoryPostProcessors(beanFactory)的执行，先大致梳理一下 refresh()逻辑吧
prepareRefresh()准备一些刷新操作，然后obtainFreshBeanFactory()方法实际上就是获取上文Spring BeanDefinition的解析过程源码分析(上)中的下面这部分

然后调用invokeBeanFactoryPostProcessors(beanFactory)方法得到一些需要注册为Bean的class并存储在beanFactory的

对染这里还未执行invokeBeanFactoryPostProcessors(beanFactory)方法，这里在上文中Spring BeanDefinition的解析过程源码分析(上)中的this()、register(annotatedClasses)方法中就添加了这些元数据！那么下面我们开始执行invokeBeanFactoryPostProcessors(beanFactory);方法！

执行invokeBeanFactoryPostProcessors(beanFactory);

	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		//传入Bean工厂并获取容器中的Bean工厂后置处理器(注意这里Bean工厂后置处理器还没有初始化)
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
		..........
	}

PostProcessorRegistrationDelegate

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

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

		//判断我们的beanFactory是否实现了BeanDefinitionRegistry
		if (beanFactory instanceof BeanDefinitionRegistry) {
			//强行把beanFactory转为BeanDefinitionRegistry
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			//保存BeanFactoryPostProcessor类型的后置处理器
			List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
			//保存BeanDefinitionRegistryPostProcessor类型的后置处理器
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

			 //循环我们传递进来的beanFactoryPostProcessors
			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				//判断我们的后置处理器是不是BeanDefinitionRegistryPostProcessor
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					//进行强制转化
					BeanDefinitionRegistryPostProcessor registryProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
					//调用它的后置方法
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					//添加到我们用于保存的BeanDefinitionRegistryPostProcessor的集合中
					registryProcessors.add(registryProcessor);
				}
				else {
					//若没有实现BeanDefinitionRegistryPostProcessor接口，那么他就是BeanFactoryPostProcessor 把当前的后置处理器加入到regularPostProcessors中
					regularPostProcessors.add(postProcessor);
				}
			}

			//定义一个集合用户保存当前准备创建的BeanDefinitionRegistryPostProcessor
			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

			//第一步:去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			//循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
			for (String ppName : postProcessorNames) {
				//判断是否实现了PriorityOrdered接口的
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					//显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					//同时也加入到processedBeans集合中去
					processedBeans.add(ppName);
				}
			}
			//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			//把他加入到用于保存到registryProcessors中
			registryProcessors.addAll(currentRegistryProcessors);
			/**
             * 在这里典型的BeanDefinitionRegistryPostProcessor就是ConfigurationClassPostProcessor
             * 用于进行bean定义的加载 比如我们的包扫描，@import等
             */
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			//调用完之后，马上clear
			currentRegistryProcessors.clear();

			//下一步 又去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			 //循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
			for (String ppName : postProcessorNames) {
				//表示没有被处理过,且实现了Ordered接口的
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					//显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					//同时也加入到processedBeans集合中去
					processedBeans.add(ppName);
				}
			}
			//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			//把他加入到用于保存到registryProcessors中
			registryProcessors.addAll(currentRegistryProcessors);
			//调用他的后置处理方法
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			//调用完之后，马上clear
			currentRegistryProcessors.clear();

			//调用没有实现任何优先级接口的BeanDefinitionRegistryPostProcessor
            //定义一个重复处理的开关变量 默认值为true
			boolean reiterate = true;
			//第一次就可以进来
			while (reiterate) {
				//进入循环马上把开关变量给改为false
				reiterate = false;
				//去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				//循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
				for (String ppName : postProcessorNames) {
					//没有被处理过的
					if (!processedBeans.contains(ppName)) {
						//显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						//同时也加入到processedBeans集合中去
						processedBeans.add(ppName);
						//再次设置为true
						reiterate = true;
					}
				}
				//对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				//把他加入到用于保存到registryProcessors中
				registryProcessors.addAll(currentRegistryProcessors);
				//调用他的后置处理方法
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				//进行clear
				currentRegistryProcessors.clear();
			}

			//调用实现了BeanDefinitionRegistryPostProcessor的接口 他是他也同时实现了BeanFactoryPostProcessor的方法
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			//调用BeanFactoryPostProcessor
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {//若当前的beanFactory没有实现了BeanDefinitionRegistry 直接调用beanFactoryPostProcessor接口的方法进行后置处理
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		//最后一步 获取容器中所有的 BeanFactoryPostProcessor
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		//保存BeanFactoryPostProcessor类型实现了priorityOrdered
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		//保存BeanFactoryPostProcessor类型实现了Ordered接口的
		List<String> orderedPostProcessorNames = new ArrayList<>();
		//保存BeanFactoryPostProcessor没有实现任何优先级接口的
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			//processedBeans包含的话，表示在上面处理BeanDefinitionRegistryPostProcessor的时候处理过了
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			//判断是否实现了PriorityOrdered
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			//判断是否实现了Ordered
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			//没有实现任何的优先级接口的
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		//先调用BeanFactoryPostProcessor实现了PriorityOrdered接口的
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		//再调用BeanFactoryPostProcessor实现了Ordered.
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		//调用没有实现任何方法接口的
		List<BeanFactoryPostProcessor> 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();

}

别看这里这么多方法，这里重点我们看第一个invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法！

切入invokeBeanDefinitionRegistryPostProcessors()方法

PostProcessorRegistrationDelegate

private static void invokeBeanDefinitionRegistryPostProcessors(
			Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {

		for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
			postProcessor.postProcessBeanDefinitionRegistry(registry);
		}
	}

执行postProcessBeanDefinitionRegistry(registry)方法
ConfigurationClassPostProcessor

@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
		......
		//真正的解析我们的Bean定义
		processConfigBeanDefinitions(registry);
	}

这个方法就比较核心了，这个方法也就是找到符合Spring Bean规则的class如下！

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		 
		List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
		//获取Spring IoC容器中目前所有Bean定义的名称
		String[] candidateNames = registry.getBeanDefinitionNames();
		//循环所有的Bean定义信息
		for (String beanName : candidateNames) {
			//通过Bean的名称来获取Bean的定义对象
			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
			//判断是否有没有解析过
			if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
					ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
				if (logger.isDebugEnabled()) {
					logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
				}
			}
			//判断是否是配置类
			// checkConfigurationClassCandidate()会判断一个是否是一个配置类,并为BeanDefinition设置属性为lite或者full。
			//在这儿为BeanDefinition设置lite和full属性值是为了后面在使用
			// 如果加了@Configuration，那么对应的BeanDefinition为full;
			// 如果加了@Bean,@Component,@ComponentScan,@Import,@ImportResource这些注解，则为lite。
			//lite和full均表示这个BeanDefinition对应的类是一个配置类
			else if (ConfigurationClassUtils.checkConfiguration
			ClassCandidate(beanDef, this.metadataReaderFactory)) {
				//添加到候选的配置类集合中
				configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
			}
		}

		// 若没有找到配置类 直接返回
		if (configCandidates.isEmpty()) {
			return;
		}

		//对我们的配置类进行Order排序
		configCandidates.sort((bd1, bd2) -> {
			int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
			int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
			return Integer.compare(i1, i2);
		});

		//创建@CompentScan、@Import导入进来的bean名称的生成器
		SingletonBeanRegistry sbr = null;
		if (registry instanceof SingletonBeanRegistry) {
			sbr = (SingletonBeanRegistry) registry;
			if (!this.localBeanNameGeneratorSet) {
				// beanName的生成器，因为后面会扫描出所有加入到spring容器中calss类，然后把这些class
				// 解析成BeanDefinition类，此时需要利用BeanNameGenerator为这些BeanDefinition生成beanName
				BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
				if (generator != null) {
					//设置@CompentScan导入进来的bean的名称生成器
					this.componentScanBeanNameGenerator = generator;
					//设置@Import导入进来的bean的名称生成器
					this.importBeanNameGenerator = generator;
				}
			}
		}

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

		 //创建一个配置类解析器对象
		ConfigurationClassParser parser = new ConfigurationClassParser(
				this.metadataReaderFactory, this.problemReporter, this.environment,
				this.resourceLoader, this.componentScanBeanNameGenerator, registry);

		//创建一个集合用于保存我们的配置类BeanDefinitionHolder集合默认长度是配置类集合的长度
		Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
		//创建一个集合用于保存我们的已经解析的配置类，长度默认为解析出来默认的配置类的集合长度
		Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
		do {
			//真正的解析我们的配置类
			parser.parse(candidates);
			parser.validate();
			//解析出来的配置类
			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());
			}
			//真正的把我们解析出来的配置类注册到容器中
			this.reader.loadBeanDefinitions(configClasses);
			//加入到已经解析的集合中
			alreadyParsed.addAll(configClasses);

			candidates.clear();
			//判断我们Spring IoC容器中Bean的定义数量是否 > 候选原始的bean定义的个数
			if (registry.getBeanDefinitionCount() > candidateNames.length) {
				//获取所有的bean定义
				String[] newCandidateNames = registry.getBeanDefinitionNames();
				//原始的老的候选的bean定义
				Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
				Set<String> alreadyParsedClasses = new HashSet<>();
				//赋值已经解析的
				for (ConfigurationClass configurationClass : alreadyParsed) {
					alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
				}
				for (String candidateName : newCandidateNames) {
					//表示当前循环的还没有被解析过
					if (!oldCandidateNames.contains(candidateName)) {
						//判断有没有被解析过
						BeanDefinition bd = registry.getBeanDefinition(candidateName);
						if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
								!alreadyParsedClasses.contains(bd.getBeanClassName())) {
							candidates.add(new BeanDefinitionHolder(bd, candidateName));
						}
					}
				}
				candidateNames = newCandidateNames;
			}
		}
		//存在没有解析过的 需要循环解析
		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();
		}
	}

这里代码也挺多的，其核心代码在于parser.parse(candidates);和this.reader.loadBeanDefinitions(configClasses);
关于this.reader.loadBeanDefinitions(configClasses)放在文末讲

切入parser.parse(candidates);

	public void parse(Set<BeanDefinitionHolder> configCandidates) {
		for (BeanDefinitionHolder holder : configCandidates) {
			BeanDefinition bd = holder.getBeanDefinition();
			try {
				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);
			}
		}

		this.deferredImportSelectorHandler.process();
	}

这里其实是根据BeanDefinition 的不同，传入不同的入参！核心调用的还是同一个方法processConfigurationClass()！

	protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
		//把我们的配置类源信息和beanName包装成一个ConfigurationClass对象
		processConfigurationClass(new ConfigurationClass(metadata, beanName));
	}

切入processConfigurationClass()
该方法主要就是循环调用doProcessConfigurationClass(configClass, sourceClass);方法将符合Bean特征的class添加到BeanDefinitionMap中，然后将配置类添加到configurationClasses中

	protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
		if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
			return;
		}

		//获取我们的配置类对象
		ConfigurationClass existingClass = this.configurationClasses.get(configClass);
		 //传入的配置类是通过其他配置类的Import导入进来的
		if (existingClass != null) {
			if (configClass.isImported()) {
				if (existingClass.isImported()) {
					//需要合并配置
					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);
			}
		}

		// 处理配置类，由于配置类可能存在父类(若父类的全类名是以java开头的，则除外)，所有需要将configClass变成sourceClass去解析，然后返回sourceClass的父类。
		// 如果此时父类为空，则不会进行while循环去解析，如果父类不为空，则会循环的去解析父类
		// SourceClass的意义：简单的包装类，目的是为了以统一的方式去处理带有注解的类，不管这些类是如何加载的
		SourceClass sourceClass = asSourceClass(configClass);
		//真正的进行配置类的解析
		do {
			//解析我们的配置类
			sourceClass = doProcessConfigurationClass(configClass, sourceClass);
		}
		while (sourceClass != null);
		
		// 将解析的配置类存储起来，这样回到parse()方法时，能取到值
		this.configurationClasses.put(configClass, configClass);
	}

切入doProcessConfigurationClass(configClass, sourceClass);

@Nullable
	protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
			throws IOException {

		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
			// 处理内部类，处理内部类时，最终还是调用doProcessConfigurationClass()方法
			processMemberClasses(configClass, sourceClass);
		}

		//处理我们的@PropertySources注解的
		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");
			}
		}

		//处理@ComponentScan或者@ComponentScans注解
        //从先找出类上的@ComponentScan和@ComponentScans注解的所有属性(例如basePackages等属性值)
		Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
		if (!componentScans.isEmpty() &&
				!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
			//循环解析（我们解析出来的AnnotationAttributes）
			for (AnnotationAttributes componentScan : componentScans) {
				//解析@ComponentScan和@ComponentScans配置的扫描的包所包含的类
				// 比如 basePackages = com.tiantang.study, 那么在这一步会扫描出这个包及子包下的class，然后将其解析成BeanDefinition
				// (BeanDefinition可以理解为等价于BeanDefinitionHolder)
				//把我们扫描出来的类变为bean定义的集合
				Set<BeanDefinitionHolder> scannedBeanDefinitions =
						this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
				// 通过上一步扫描包com.tiantang.com下的类，有可能扫描出来的bean中可能也添加了ComponentScan或者ComponentScans注解.
				//所以这里需要循环遍历一次，进行递归(parse)，继续解析，直到解析出的类上没有ComponentScan和ComponentScans
				// (这时3.1这一步解析出componentScans为空列表，不会进入到if语句，递归终止)
				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
					if (bdCand == null) {
						bdCand = holder.getBeanDefinition();
					}
					//判断当前扫描出来的bean定义是不是一个配置类,若是的话 直接进行递归解析
					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
						//递归解析
						parse(bdCand.getBeanClassName(), holder.getBeanName());
					}
				}
			}
		}

		//处理Import注解注册的bean，这一步只会将import注册的bean变为ConfigurationClass,不会变成BeanDefinition
		// 而是在loadBeanDefinitions()方法中变成BeanDefinition，再放入到BeanDefinitionMap中
		// 关于Import注解,后面会单独写文章介绍
		processImports(configClass, sourceClass, getImports(sourceClass), true);

		//处理@ImportResource注解引入的
		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);
			}
		}

		//处理@Bean methods获取到我们配置类中所有标注了@Bean的方法
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}

		//处理配置类接口的
		processInterfaces(configClass, sourceClass);

		//处理配置类的父类的
		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();
			}
		}

		//没有父类解析完成
		return null;
	}

其中有个很重要的方法this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());和ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)
先讲checkConfigurationClassCandidate，因为this.componentScanParser.parse方法调用栈比较长！
切入checkConfigurationClassCandidate

该方法是用来判断一个是否是一个配置类，并为BeanDefinition设置属性为lite或者full。如果加了@Configuration，那么对应的BeanDefinition为full，如果加了@Bean，@Component，@ComponentScan，@Import，@ImportResource这些注解，则为lite。lite和full均表示这个BeanDefinition对应的类是一个配置类。
public static boolean checkConfigurationClassCandidate(BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
	// ... 省略部分不重要的代码
	if (isFullConfigurationCandidate(metadata)) {
		// 含有@Configuration注解，那么对应的BeanDefinition的configurationClass属性值设置为full
		beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
	}
	else if (isLiteConfigurationCandidate(metadata)) {
		// 含有@Bean,@Component,@ComponentScan,@Import,@ImportResource注解
		// configurationClass属性值设置为lite
		beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
	}
	else {
		return false;
	}
	return true;
}

切入this.componentScanParser.parse()

	public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
		//给扫描器设置beanName的生成器对象
		ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
				componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);

		Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
		boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
		scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
				BeanUtils.instantiateClass(generatorClass));
		
		//设置bean的域代理模型
		ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
		if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
			scanner.setScopedProxyMode(scopedProxyMode);
		}
		else {
			Class<? extends ScopeMetadataResolver> resolverClass = componentScan.getClass("scopeResolver");
			scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
		}

		scanner.setResourcePattern(componentScan.getString("resourcePattern"));
		//设置ComponentScan对象的includeFilters包含的属性
		for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
			for (TypeFilter typeFilter : typeFiltersFor(filter)) {
				scanner.addIncludeFilter(typeFilter);
			}
		}
		//设置ComponentScan对象的excludeFilters不包含的属性
		for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
			for (TypeFilter typeFilter : typeFiltersFor(filter)) {
				scanner.addExcludeFilter(typeFilter);
			}
		}
		//是否懒加载
		boolean lazyInit = componentScan.getBoolean("lazyInit");
		if (lazyInit) {
			scanner.getBeanDefinitionDefaults().setLazyInit(true);
		}
		//包路径
		Set<String> basePackages = new LinkedHashSet<>();
		String[] basePackagesArray = componentScan.getStringArray("basePackages");
		for (String pkg : basePackagesArray) {
			String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg),
					ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
			Collections.addAll(basePackages, tokenized);
		}
		for (Class<?> clazz : componentScan.getClassArray("basePackageClasses")) {
			basePackages.add(ClassUtils.getPackageName(clazz));
		}
		if (basePackages.isEmpty()) {
			basePackages.add(ClassUtils.getPackageName(declaringClass));
		}

		scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
			@Override
			protected boolean matchClassName(String className) {
				return declaringClass.equals(className);
			}
		});
		//真正的进行扫描解析
		return scanner.doScan(StringUtils.toStringArray(basePackages));
	}

切入scanner.doScan(StringUtils.toStringArray(basePackages))
doScan方法主要是实现了扫描的逻辑，也就是通过findCandidateComponents(basePackage)方法扫描指定包下的符合Bean特征的class，然后存放到candidates ，然后通过一系列判断进入registerBeanDefinition方法，将符合Bean特征的Bean注册到beanDefinitionMap中去

	//类路径Bean定义扫描器扫描给定包及其子包
	protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
		Assert.notEmpty(basePackages, "At least one base package must be specified");
		//创建bean定义的holder对象用于保存扫描后生成的bean定义对象
		Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
		//循环我们的包路径集合
		for (String basePackage : basePackages) {
			//调用父类ClassPathScanningCandidateComponentProvider的方法
			//扫描给定类路径，获取符合条件的Bean定义
			Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
			//遍历扫描到的Bean
			for (BeanDefinition candidate : candidates) {
				//获取@Scope注解的值，即获取Bean的作用域
				ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
				//为Bean设置作用域
				candidate.setScope(scopeMetadata.getScopeName());
				为Bean生成名称。也就是设置我们的beanName
				String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
				/如果扫描到的Bean不是Spring的注解Bean，则为Bean设置默认值，
				//设置Bean的自动依赖注入装配属性等
				if (candidate instanceof AbstractBeanDefinition) {
					postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
				}
				//处理jsr250相关的组件
				if (candidate instanceof AnnotatedBeanDefinition) {
					//处理注解Bean中通用的注解，在分析注解Bean定义类读取器时已经分析过
					AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
				}
				//把我们解析出来的组件bean定义注册到Spring IoC容器中
				if (checkCandidate(beanName, candidate)) {
					BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
					//根据注解中配置的作用域，为Bean应用相应的代理模式
					definitionHolder =
							AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
					beanDefinitions.add(definitionHolder);
					//注册到Spring IoC容器中
					registerBeanDefinition(definitionHolder, this.registry);
				}
			}
		}
		return beanDefinitions;
	}

其中findCandidateComponents(basePackage)和registerBeanDefinition(definitionHolder, this.registry)方法尤为重要！

切入findCandidateComponents(basePackage)

	public Set<BeanDefinition> findCandidateComponents(String basePackage) {
		if (this.componentsIndex != null && indexSupportsIncludeFilters()) {
			return addCandidateComponentsFromIndex(this.componentsIndex, basePackage);
		}
		else {
			return scanCandidateComponents(basePackage);
		}
	}

执行scanCandidateComponents方法

该方法的核心逻辑就是在指定的包路径下，及其子包扫描符合规则的类，并收集为candidates返回

	private Set<BeanDefinition> scanCandidateComponents(String basePackage) {
		Set<BeanDefinition> candidates = new LinkedHashSet<>();
		try {
			//补全扫描路径，扫描所有.class文件 classpath*:com/mydemo/**/*.class
			String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
					resolveBasePackage(basePackage) + '/' + this.resourcePattern;
			//定位资源
			Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);
			boolean traceEnabled = logger.isTraceEnabled();
			boolean debugEnabled = logger.isDebugEnabled();
			for (Resource resource : resources) {
				if (traceEnabled) {
					logger.trace("Scanning " + resource);
				}
				if (resource.isReadable()) {
					try {
						//通过ASM获取class元数据，并封装在MetadataReader元数据读取器中
						MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);
						//判断该类是否符合@CompoentScan的过滤规则
						//过滤匹配排除excludeFilters排除过滤器(可以没有),包含includeFilter中的包含过滤器（至少包含一个）。
						if (isCandidateComponent(metadataReader)) {
							//把元数据转化为 BeanDefinition
							ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
							sbd.setResource(resource);
							sbd.setSource(resource);
							//判断是否是合格的bean定义
							if (isCandidateComponent(sbd)) {
								if (debugEnabled) {
									logger.debug("Identified candidate component class: " + resource);
								}
								//加入到集合中
								candidates.add(sbd);
							}
							else {
								//不合格 不是顶级类、具体类
								if (debugEnabled) {
									logger.debug("Ignored because not a concrete top-level class: " + resource);
								}
							}
						}
						else {
							//不符@CompoentScan过滤规则
							if (traceEnabled) {
								logger.trace("Ignored because not matching any filter: " + resource);
							}
						}
					}
					catch (Throwable ex) {
						throw new BeanDefinitionStoreException(
								"Failed to read candidate component class: " + resource, ex);
					}
				}
				else {
					if (traceEnabled) {
						logger.trace("Ignored because not readable: " + resource);
					}
				}
			}
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
		}
		return candidates;
	}

这里有个判断是否符合过滤规则的方法isCandidateComponent()
切入isCandidateComponent()
判断元信息读取器读取的类是否符合容器定义的注解过滤规则

	//@CompoentScan的过滤规则支持5种 （注解、类、正则、aop、自定义）
	protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
		//如果读取的类的注解在排除注解过滤规则中，返回false
		for (TypeFilter tf : this.excludeFilters) {
			if (tf.match(metadataReader, getMetadataReaderFactory())) {
				return false;
			}
		}
		//如果读取的类的注解在包含的注解的过滤规则中，则返回ture
		for (TypeFilter tf : this.includeFilters) {
			//判断当前类的注解是否match规则
			if (tf.match(metadataReader, getMetadataReaderFactory())) {
				//是否有@Conditional注解，进行相关处理
				return isConditionMatch(metadataReader);
			}
		}
		return false;
	}

来都来了，看看match方法如何实现的吧！
tf.match()

	@Override
	public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory)
			throws IOException {

		//检查当前类的注解是否符合规律规则
		if (matchSelf(metadataReader)) {
			return true;
		}
		//check 类名是否符合规则
		ClassMetadata metadata = metadataReader.getClassMetadata();
		if (matchClassName(metadata.getClassName())) {
			return true;
		}
		//如果有继承父类
		if (this.considerInherited) {
			String superClassName = metadata.getSuperClassName();
			if (superClassName != null) {
				// Optimization to avoid creating ClassReader for super class.
				Boolean superClassMatch = matchSuperClass(superClassName);
				if (superClassMatch != null) {
					if (superClassMatch.booleanValue()) {
						return true;
					}
				}
				else {
					// Need to read super class to determine a match...
					try {
						if (match(metadata.getSuperClassName(), metadataReaderFactory)) {
							return true;
						}
					}
					catch (IOException ex) {
						logger.debug("Could not read super class [" + metadata.getSuperClassName() +
								"] of type-filtered class [" + metadata.getClassName() + "]");
					}
				}
			}
		}
		//如果有实现接口
		if (this.considerInterfaces) {
			for (String ifc : metadata.getInterfaceNames()) {
				// Optimization to avoid creating ClassReader for super class
				Boolean interfaceMatch = matchInterface(ifc);
				if (interfaceMatch != null) {
					if (interfaceMatch.booleanValue()) {
						return true;
					}
				}
				else {
					// Need to read interface to determine a match...
					try {
						if (match(ifc, metadataReaderFactory)) {
							return true;
						}
					}
					catch (IOException ex) {
						logger.debug("Could not read interface [" + ifc + "] for type-filtered class [" +
								metadata.getClassName() + "]");
					}
				}
			}
		}

		return false;
	}

我们接着matchSelf方法深入

	protected boolean matchSelf(MetadataReader metadataReader) {
		//获取注解元数据
		AnnotationMetadata metadata = metadataReader.getAnnotationMetadata();
		//check 注解及其派生注解中是否包含@Component
		//获取当前类的注解 metadata.hasAnnotation    @Controller
		//获取当前类的注解及其派生注解 metadata.hasAnnotation   @Controller包含的@Component\@Documented等等
		return metadata.hasAnnotation(this.annotationType.getName()) ||
				(this.considerMetaAnnotations && metadata.hasMetaAnnotation(this.annotationType.getName()));
	}

这段代码可以解决Spring发现@Configuration、@Controller、@Service这些注解修饰的类的，在这些注解底层都是使用@Component的派生注解，而spring通过metadata.hasMetaAnnotation()方法获取到这些注解包含@Component，所以都可以扫描到

执行registerBeanDefinition(definitionHolder, this.registry)

	protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
	}

	public static void registerBeanDefinition(
			BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
			throws BeanDefinitionStoreException {

		// Register bean definition under primary name.
		String beanName = definitionHolder.getBeanName();
		registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

		// Register aliases for bean name, if any.
		String[] aliases = definitionHolder.getAliases();
		if (aliases != null) {
			for (String alias : aliases) {
				registry.registerAlias(beanName, alias);
			}
		}
	}

registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

	@Override
	public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
			throws BeanDefinitionStoreException {

		
		
		BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
		if (existingDefinition != null) {
			......
		}
		else {
			if (hasBeanCreationStarted()) {
				// Cannot modify startup-time collection elements anymore (for stable iteration)
				synchronized (this.beanDefinitionMap) {
					this.beanDefinitionMap.put(beanName, beanDefinition);
					List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
					updatedDefinitions.addAll(this.beanDefinitionNames);
					updatedDefinitions.add(beanName);
					this.beanDefinitionNames = updatedDefinitions;
					if (this.manualSingletonNames.contains(beanName)) {
						Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
						updatedSingletons.remove(beanName);
						this.manualSingletonNames = updatedSingletons;
					}
				}
			}
			else {
				// Still in startup registration phase
				this.beanDefinitionMap.put(beanName, beanDefinition);
				this.beanDefinitionNames.add(beanName);
				this.manualSingletonNames.remove(beanName);
			}
			this.frozenBeanDefinitionNames = null;
		}

		if (existingDefinition != null || containsSingleton(beanName)) {
			resetBeanDefinition(beanName);
		}
	}

那么这里this.beanDefinitionMap.put(beanName, beanDefinition);就是添加beanDefinitionMap中的核心方法

切入this.reader.loadBeanDefinitions(configClasses)

该方法实际上是将通过@Import、@Bean等注解方式注册的类解析成BeanDefinition，然后注册到BeanDefinitionMap中。

	public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
		TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
		// 循环调用loadBeanDefinitionsForConfigurationClass()
		for (ConfigurationClass configClass : configurationModel) {
			loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
		}
	}

	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;
		}
		// 如果一个bean是通过@Import(ImportSelector)的方式添加到容器中的，那么此时configClass.isImported()返回的是true
		// 而且configClass的importedBy属性里面存储的是ConfigurationClass就是将bean导入的类
		 //是不是通过@Import导入进来的
		if (configClass.isImported()) {
			registerBeanDefinitionForImportedConfigurationClass(configClass);
		}
		// 判断当前的bean中是否含有@Bean注解的方法，如果有，需要把这些方法产生的bean放入到BeanDefinitionMap当中
		for (BeanMethod beanMethod : configClass.getBeanMethods()) {
			loadBeanDefinitionsForBeanMethod(beanMethod);
		}
		//是不是通过@ImportResources导入进来的
		loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
		// 如果bean上存在@Import注解，且import的是一个实现了ImportBeanDefinitionRegistrar接口,则执行ImportBeanDefinitionRegistrar的registerBeanDefinitions()方法，也就是判断是不是通过ImportBeanDefinition注解导入进来的
		loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
	}

registerBeanDefinitionForImportedConfigurationClass(configClass);
通过@Import导入进来的执行registerBeanDefinitionForImportedConfigurationClass(configClass)方法：

	private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
        //获取我们的配置类的源信息
        AnnotationMetadata metadata = configClass.getMetadata();
        //构建为我们的bean定义
        AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);
        //设置他的scope
        ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
        configBeanDef.setScope(scopeMetadata.getScopeName());
        //获取bean的名称
        String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
        //处理我们的JRS250组件的
        AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);

        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
        //注册我们的bean定义到我们的容器中
        this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
        configClass.setBeanName(configBeanName);

        if (logger.isDebugEnabled()) {
            logger.debug("Registered bean definition for imported class '" + configBeanName + "'");
        }
    }

loadBeanDefinitionsForBeanMethod(beanMethod);
通过@Bean导入进来的执行loadBeanDefinitionsForBeanMethod(beanMethod)方法：

	private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
		ConfigurationClass configClass = beanMethod.getConfigurationClass();
		MethodMetadata metadata = beanMethod.getMetadata();
		String methodName = metadata.getMethodName();
		.......
		this.registry.registerBeanDefinition(beanName, beanDefToRegister);
	}

这里又将符合Bean特征的class添加到BeanDefinitionMap中，那么至此整个invokeBeanFactoryPostProcessors(beanFactory);方法就至此完了！这里把符合Bean特征的class解析成BeanDefinition存储在beanFactory中

然后后期通过finishBeanFactoryInitialization(beanFactory)方法实例化这些Bean的操作！

这篇关于Spring BeanDefinition的解析过程源码分析(下)的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！