Spring配置类源码分析详解

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		List<BeanDefinitionHolder> confiGCandidates = new ArrayList<>();
		//拿到启动过程中注入的类的名称
		String[] candidateNames = registry.getBeanDefinitionNames();
		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);
				}
			}
			//判断是不是配置类
			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
		// 通过@Order可以排序，升序排序，order越下越靠前
		configCandidates.sort((bd1, bd2) -> {
			int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
			int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
			return Integer.compare(i1, i2);
		});
		// Parse each @Configuration class
		//构建一个配置类的解析器
		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());
		// 递归解析配置类，有可能通过解析一个配置类，得到了其他的配置类，比如扫描和Import
		do {
			StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");
			//配置类解析
			parser.parse(candidates);
			parser.validate();
			// 从解析器parse得到配置类，移除已经解析过的，剩下的就是新增的
			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());
			}
			// 把parser.parse(candidates);解析到的但是未生成BeanDefinition的配置 生成对应的BeanDefinition
			this.reader.loadBeanDefinitions(configClasses);
			alreadyParsed.addAll(configClasses);
			processConfig.tag("classCount", () -> String.valueOf(configClasses.size())).end();
			// candidates中存的是BeanDefinition，configClasses中存的是ConfigurationClass
			candidates.clear();
			//loadBeanDefinitions方法会增加很多BeanDefinition 如果发现BeanDefinition增加了，则有可能增加了配置类
			//这个if对新增的BeanDefinition做处理
			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());
				}
				//遍历新增的BeanDefinition
				for (String candidateName : newCandidateNames) {
					if (!oldCandidateNames.contains(candidateName)) {
						BeanDefinition bd = registry.getBeanDefinition(candidateName);
						//判断新增的BeanDefinition是不是一个配置类
						if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
								!alreadyParsedClasses.contains(bd.getBeanClassName())) {
							//如果是配置类 添加到这个集合当中 交给do while 循环解析配置类
							candidates.add(new BeanDefinitionHolder(bd, candidateName));
						}
					}
				}
				candidateNames = newCandidateNames;
			}
		}
		while (!candidates.isEmpty());
	}

public static boolean checkConfigurationClassCandidate(
			BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
		String className = beanDef.getBeanClassName();
		if (className == null || beanDef.getFactoryMethodName() != null) {
			return false;
		}
		// AnnotationMetadata表示某个类的注解信息，但是并一定要加载这个类
		AnnotationMetadata metadata;
		// 如果AnnotatedBeanDefinition，则直接取AnnotationMetadata
		if (beanDef instanceof AnnotatedBeanDefinition &&
				className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
			// Can reuse the pre-parsed metadata from the given BeanDefinition...
			metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();
		}
		// 如果是AbstractBeanDefinition，则解析beanClass得到AnnotationMetadata
		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;
			}
		}
		//如果该类有@Configuration注解 表示是一个配置类
		Map<String, Object> config = metadata.getAnnotationAttributes(Configuration.class.getName());
		// 存在@Configuration，并且proxyBeanMethods不为false(为true或为null)时，就是Full配置类
		if (config != null && !Boolean.FALSE.equals(config.get("proxyBeanMethods"))) {
			beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
		// 存在@Configuration，并且proxyBeanMethods为false时，是lite配置类
		// 或者不存在@Configuration，但是只要存在@Component、@ComponentScan、@Import、@ImportResource四个中的一个，就是lite配置类
		// 或者不存在@Configuration，只要存在@Bean注解了的方法，就是lite配置类
		else if (config != null || isConfigurationCandidate(metadata)) {
			beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
		}
		else {
			return false;
		}
		// 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;
	}

public static boolean isConfigurationCandidate(AnnotationMetadata metadata) {
		//如果是一个接口类型，那么直接返回false 就不是一个配置类
		if (metadata.isInterface()) {
			return false;
		}
		// 只要存在@Component、@ComponentScan、@Import、@ImportResource四个中的一个，就是lite配置类
		for (String indicator : candidateIndicators) {
			if (metadata.isAnnotated(indicator)) {
				return true;
			}
		}
		// 只要存在@Bean注解了的方法，就是lite配置类
		return hasBeanMethods(metadata);
	}
static {
		candidateIndicators.add(Component.class.getName());
		candidateIndicators.add(ComponentScan.class.getName());
		candidateIndicators.add(Import.class.getName());
		candidateIndicators.add(ImportResource.class.getName());
	}

protected void processConfigurationClass(ConfigurationClass configClass, Predicate<String> filter) throws IOException {
		// 条件注解判断
		if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
			return;
		}
		ConfigurationClass existingClass = this.configurationClasses.get(configClass);
		if (existingClass != null) {
			if (configClass.isImported()) {
				// OrderService导入了AccountService，UserService也导入了AccountService，就会符合这个条件
				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);
			}
		}
		// Recursively process the configuration class and its superclass hierarchy.
		SourceClass sourceClass = asSourceClass(configClass, filter);
		//循环 解析了该类后 解析父类
		do {
			//核心方法 真正解析类 --> 解析类上的各种配置注解并做出对应处理
			sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
		}
		while (sourceClass != null);
		// ConfigurationClass重写了equals方法，只要两个ConfigurationClass对应的className相等就可以
		this.configurationClasses.put(configClass, configClass);
	}

	protected final SourceClass doProcessConfigurationClass(
			ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
			throws IOException {
		//对@Component注解做处理
		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
			// 处理内部类
			proceSSMemberClasses(configClass, sourceClass, filter);
		}
		//对@PropertySource注解做处理
		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");
			}
		}
		//对@ComponentScan注解做处理
		Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
		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
				// 底层调用doScan 进行扫描所有的bean得到BeanDefinition
				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
				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
					if (bdCand == null) {
						bdCand = holder.getBeanDefinition();
					}
					// 检查扫描出来的BeanDefinition是不是配置类（full和lite）
					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
						//如果是配置类递归执行 解析配置类的方法
						parse(bdCand.getBeanClassName(), holder.getBeanName());
					}
				}
			}
		}
		// getImports(sourceClass)会拿到所有导入的类
		//对@Import注解做处理
		processImports(configClass, sourceClass, getImports(sourceClass), filter, true);
		//对@ImportResource注解做处理 @ImportResource导入一个xml作为配置文件 这里暂时没有解析xml文件
		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
		// 解析配置类中的@Bean，但并没有真正处理@Bean，只是暂时找出来
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}
		// Process default methods on interfaces
		// 解析配置类所实现的接口中的@Bean，但并没有真正处理@Bean，只是暂时找出来
		processInterfaces(configClass, sourceClass);
		// Process superclass, if any
		//如果有父类就返回父类
		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();
			}
		}
		//如果没有父类 那么这个类就解析完了
		return null;
	}

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;
		}
		//将Importe和@component的内部类 生成BeanDefinition
		if (configClass.isImported()) {
			registerBeanDefinitionForImportedConfigurationClass(configClass);
		}
		//解析所有的@bean 生成对应的BeanDefinition
		for (BeanMethod beanMethod : configClass.getBeanMethods()) {
			loadBeanDefinitionsForBeanMethod(beanMethod);
		}
		//解析导入进来的xml文件 生成bean对应的BeanDefinition
		loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
		//执行实现了ImportBeanDefinitionRegistrar接口的方法
		loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
	}

//定义一个类
public class Aaaa {
	public void test(){
		System.out.println("-----------Aaaa----------");
	}
}
//定义一个Import类
public class ImportDemo {
	@Bean
	public Aaaa aaaa(){
		return new Aaaa();
	}
}

@ComponentScan(basePackages = {"service","config","aop"})
@Configuration
@Import(ImportDemo.class)
public class AppConfig {
}
public class Test {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
		Aaaa aaaa = (Aaaa)context.getBean("aaaa");
		aaaa.test();
	}
}