文章目录

• 一、源码时序图
• 二、源码解析
• • 1. 运行案例程序启动类
  • 2. 解析AnnotationConfigApplicationContext类的AnnotationConfigApplicationContext(Class... componentClasses)构造方法
  • 3. 解析AbstractApplicationContext类的refresh()方法
  • 4. 解析AbstractApplicationContext类的invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory)方法
  • 5. 解析PostProcessorRegistrationDelegate类的invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, ListbeanFactoryPostProcessors)方法
  • 6. 解析PostProcessorRegistrationDelegate类的invokeBeanDefinitionRegistryPostProcessors(Collection postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup)方法
  • 7. 解析ConfigurationClassPostProcessor类的postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)方法
  • 8. 解析ConfigurationClassPostProcessor类的processConfigBeanDefinitions(BeanDefinitionRegistry registry)方法
  • 9. 解析ConfigurationClassParser类的parse(SetconfigCandidates)方法
  • 10. 解析ConfigurationClassParser类的parse(AnnotationMetadata metadata, String beanName)方法
  • 11. 解析ConfigurationClassParser类的processConfigurationClass(ConfigurationClass configClass, Predicatefilter)方法
  • 12. 解析ConfigurationClassParser类的doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass, Predicatefilter)方法
  • 13. 解析ComponentScanAnnotationParser类的parse(AnnotationAttributes componentScan, String declaringClass)方法
  • 14. 解析ClassPathBeanDefinitionScanner类的doScan(String... basePackages)方法
  • 15. 解析ClassPathScanningCandidateComponentProvider类的findCandidateComponents(String basePackage)方法
  • 16. 解析ClassPathScanningCandidateComponentProvider类的scanCandidateComponents(String basePackage)方法
  • 17. 解析ClassPathScanningCandidateComponentProvider类的isCandidateComponent(MetadataReader metadataReader)方法
  • 18. 回到ClassPathScanningCandidateComponentProvider类的scanCandidateComponents(String basePackage)方法
  • 19. 回到ClassPathBeanDefinitionScanner类的doScan(String... basePackages)方法
  • 20. 解析ClassPathBeanDefinitionScanner类的registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)方法
  • 21. 解析BeanDefinitionReaderUtils类的registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)方法。
  • 22. 解析DefaultListableBeanFactory类的registerBeanDefinition(String beanName, BeanDefinition beanDefinition)方法

一、源码时序图

以源码时序图的方式，直观的感受下@ComponentScans注解与@ComponentScan注解在Spring源码层面的执行流程。@ComponentScans注解与@ComponentScan注解在Spring源码层面的执行流程如图所示：

由图可以看出，解析@ComponentScans注解与@ComponentScan注解在Spring源码中的执行流程，会涉及到ComponentScanTest类、AnnotationConfigApplicationContext类、AbstractApplicationContext类、PostProcessorRegistrationDelegate类、ConfigurationClassPostProcessor类、ConfigurationClassParser类、ComponentScanAnnotationParser类、ClassPathBeanDefinitionScanner类、ClassPathScanningCandidateComponentProvider类、BeanDefinitionReaderUtils类和DefaultListableBeanFactory类等。具体的源码执行细节参见源码解析部分。

二、源码解析

@ComponentScans注解与@ComponentScan注解在Spring源码中的执行流程，结合源码执行的时序图，会理解的更加深刻。

1. 运行案例程序启动类

public static void main(String[] args) {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ComponentScanConfig.class);String[] names = context.getBeanDefinitionNames();Arrays.stream(names).forEach(System.out::println);
}

可以看到，在ComponentScanTest类的main()方法中调用了AnnotationConfigApplicationContext类的构造方法，并传入了ComponentScanConfig类的Class对象来创建IOC容器。接下来，会进入AnnotationConfigApplicationContext类的构造方法。

2. 解析AnnotationConfigApplicationContext类的AnnotationConfigApplicationContext(Class… componentClasses)构造方法

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

可以看到，在上述构造方法中，调用了refresh()方法来刷新IOC容器。

3. 解析AbstractApplicationContext类的refresh()方法

@Override
public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {//############省略其他代码##############try {//############省略其他代码##############invokeBeanFactoryPostProcessors(beanFactory);//############省略其他代码##############}catch (BeansException ex) {//############省略其他代码##############}finally {//############省略其他代码##############}}
}

refresh()方法是Spring中一个非常重要的方法，很多重要的功能和特性都是通过refresh()方法进行注入的。可以看到，在refresh()方法中，调用了invokeBeanFactoryPostProcessors()方法。

4. 解析AbstractApplicationContext类的invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory)方法

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

可以看到，在AbstractApplicationContext类的invokeBeanFactoryPostProcessors()方法中调用了PostProcessorRegistrationDelegate类的invokeBeanFactoryPostProcessors()方法。

5. 解析PostProcessorRegistrationDelegate类的invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, ListbeanFactoryPostProcessors)方法

由于方法的源码比较长，这里，只关注当前最核心的逻辑，如下所示：

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List beanFactoryPostProcessors) {//############省略其他代码##############List currentRegistryProcessors = new ArrayList<>();// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.String[] postProcessorNames =beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);for (String ppName : postProcessorNames) {if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));processedBeans.add(ppName);}}sortPostProcessors(currentRegistryProcessors, beanFactory);registryProcessors.addAll(currentRegistryProcessors);invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());currentRegistryProcessors.clear();// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);for (String ppName : postProcessorNames) {if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));processedBeans.add(ppName);}}sortPostProcessors(currentRegistryProcessors, beanFactory);registryProcessors.addAll(currentRegistryProcessors);invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());currentRegistryProcessors.clear();// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.boolean reiterate = true;while (reiterate) {reiterate = false;postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);for (String ppName : postProcessorNames) {if (!processedBeans.contains(ppName)) {currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));processedBeans.add(ppName);reiterate = true;}}sortPostProcessors(currentRegistryProcessors, beanFactory);registryProcessors.addAll(currentRegistryProcessors);invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());currentRegistryProcessors.clear();}//############省略其他代码##############
}

可以看到，在PostProcessorRegistrationDelegate类的invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, ListbeanFactoryPostProcessors)方法中，BeanDefinitionRegistryPostProcessor的实现类在执行逻辑上会有先后顺序，并且最终都会调用invokeBeanDefinitionRegistryPostProcessors()方法。

6. 解析PostProcessorRegistrationDelegate类的invokeBeanDefinitionRegistryPostProcessors(Collection postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup)方法

private static void invokeBeanDefinitionRegistryPostProcessors(Collection postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup) {for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {StartupStep postProcessBeanDefRegistry = applicationStartup.start("spring.context.beandef-registry.post-process").tag("postProcessor", postProcessor::toString);postProcessor.postProcessBeanDefinitionRegistry(registry);postProcessBeanDefRegistry.end();}
}

可以看到，在invokeBeanDefinitionRegistryPostProcessors()方法中，会循环遍历postProcessors集合中的每个元素，调用postProcessBeanDefinitionRegistry()方法注册Bean的定义信息。

7. 解析ConfigurationClassPostProcessor类的postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)方法

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {//##########省略其他代码###################processConfigBeanDefinitions(registry);
}

可以看到，在postProcessBeanDefinitionRegistry()方法中，会调用processConfigBeanDefinitions()方法。

8. 解析ConfigurationClassPostProcessor类的processConfigBeanDefinitions(BeanDefinitionRegistry registry)方法

这里，重点关注方法中的如下逻辑：

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {//############省略其他代码#################// Parse each @Configuration classConfigurationClassParser parser = new ConfigurationClassParser(this.metadataReaderFactory, this.problemReporter, this.environment,this.resourceLoader, this.componentScanBeanNameGenerator, registry);Set candidates = new LinkedHashSet<>(configCandidates);Set alreadyParsed = new HashSet<>(configCandidates.size());do {StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");parser.parse(candidates);parser.validate();//############省略其他代码#################}while (!candidates.isEmpty());//############省略其他代码#################
}

可以看到，在processConfigBeanDefinitions()方法中，创建了一个ConfigurationClassParser类型的对象parser，并且调用了parser的parse()方法来解析类的配置信息。

9. 解析ConfigurationClassParser类的parse(SetconfigCandidates)方法

public void parse(Set 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();
}

可以看到，在ConfigurationClassParser类的parse(SetconfigCandidates)方法中，调用了类中的另一个parse()方法。

10. 解析ConfigurationClassParser类的parse(AnnotationMetadata metadata, String beanName)方法

protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {processConfigurationClass(new ConfigurationClass(metadata, beanName), DEFAULT_EXCLUSION_FILTER);
}

可以看到，上述parse()方法的实现比较简单，直接调用了processConfigurationClass()方法。

11. 解析ConfigurationClassParser类的processConfigurationClass(ConfigurationClass configClass, Predicatefilter)方法

protected void processConfigurationClass(ConfigurationClass configClass, Predicate filter) throws IOException {//###############省略其他代码####################SourceClass sourceClass = asSourceClass(configClass, filter);do {sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);}while (sourceClass != null);this.configurationClasses.put(configClass, configClass);
}

可以看到，在processConfigurationClass()方法中，会通过do-while()循环获取配置类和其父类的注解信息，SourceClass类中会封装配置类上注解的详细信息。在processConfigurationClass()方法中，调用了doProcessConfigurationClass()方法。

12. 解析ConfigurationClassParser类的doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass, Predicatefilter)方法

protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass, Predicate filter)throws IOException {//##############省略其他代码################// Process any @ComponentScan annotationsSet 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 immediatelySet scannedBeanDefinitions =this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());// Check the set of scanned definitions for any further config classes and parse recursively if neededfor (BeanDefinitionHolder holder : scannedBeanDefinitions) {BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();if (bdCand == null) {bdCand = holder.getBeanDefinition();}if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {parse(bdCand.getBeanClassName(), holder.getBeanName());}}}}//##############省略其他代码################// No superclass -> processing is completereturn null;
}

这里，只关注与@ComponentScan注解相关的逻辑，可以看到，在上述处理@ComponentScan注解的逻辑中，通过componentScanParser的parse()方法对@ComponentScan注解进行解析。

13. 解析ComponentScanAnnotationParser类的parse(AnnotationAttributes componentScan, String declaringClass)方法

public Set parse(AnnotationAttributes componentScan, String declaringClass) {ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);Class generatorClass = componentScan.getClass("nameGenerator");boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :BeanUtils.instantiateClass(generatorClass));ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");if (scopedProxyMode != ScopedProxyMode.DEFAULT) {scanner.setScopedProxyMode(scopedProxyMode);}else {Class resolverClass = componentScan.getClass("scopeResolver");scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));}scanner.setResourcePattern(componentScan.getString("resourcePattern"));for (AnnotationAttributes includeFilterAttributes : componentScan.getAnnotationArray("includeFilters")) {List typeFilters = TypeFilterUtils.createTypeFiltersFor(includeFilterAttributes, this.environment,this.resourceLoader, this.registry);for (TypeFilter typeFilter : typeFilters) {scanner.addIncludeFilter(typeFilter);}}for (AnnotationAttributes excludeFilterAttributes : componentScan.getAnnotationArray("excludeFilters")) {List typeFilters = TypeFilterUtils.createTypeFiltersFor(excludeFilterAttributes, this.environment,this.resourceLoader, this.registry);for (TypeFilter typeFilter : typeFilters) {scanner.addExcludeFilter(typeFilter);}}boolean lazyInit = componentScan.getBoolean("lazyInit");if (lazyInit) {scanner.getBeanDefinitionDefaults().setLazyInit(true);}Set 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) {@Overrideprotected boolean matchClassName(String className) {return declaringClass.equals(className);}});return scanner.doScan(StringUtils.toStringArray(basePackages));
}

看到这里，大家是不是有一种豁然开朗的感觉，原来@ComponentScan注解是在这里解析的！！！！

可以看到，在parse()方法中，会创建一个ClassPathBeanDefinitionScanner类型的扫描器scanner，将@ComponentScan注解上配置的信息都设置到扫描器scanner中，最后调用扫描器scanner的doScan()方法进行扫描。

14. 解析ClassPathBeanDefinitionScanner类的doScan(String… basePackages)方法

protected Set doScan(String... basePackages) {Assert.notEmpty(basePackages, "At least one base package must be specified");Set beanDefinitions = new LinkedHashSet<>();for (String basePackage : basePackages) {Set candidates = findCandidateComponents(basePackage);for (BeanDefinition candidate : candidates) {ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);candidate.setScope(scopeMetadata.getScopeName());String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);if (candidate instanceof AbstractBeanDefinition) {postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);}if (candidate instanceof AnnotatedBeanDefinition) {AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);}if (checkCandidate(beanName, candidate)) {BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);definitionHolder =AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);beanDefinitions.add(definitionHolder);registerBeanDefinition(definitionHolder, this.registry);}}}return beanDefinitions;
}

在doScan()方法中，会遍历传入的每个包路径，调用findCandidateComponents()方法来扫描带有注解（例如@Component注解）的类。

15. 解析ClassPathScanningCandidateComponentProvider类的findCandidateComponents(String basePackage)方法

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

可以看到，Spring在扫描类时，会调用scanCandidateComponents()方法。

16. 解析ClassPathScanningCandidateComponentProvider类的scanCandidateComponents(String basePackage)方法

private Set scanCandidateComponents(String basePackage) {Set candidates = new LinkedHashSet<>();try {String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +resolveBasePackage(basePackage) + '/' + this.resourcePattern;Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath);boolean traceEnabled = logger.isTraceEnabled();boolean debugEnabled = logger.isDebugEnabled();for (Resource resource : resources) {String filename = resource.getFilename();if (filename != null && filename.contains(ClassUtils.CGLIB_CLASS_SEPARATOR)) {// Ignore CGLIB-generated classes in the classpathcontinue;}if (traceEnabled) {logger.trace("Scanning " + resource);}try {MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);if (isCandidateComponent(metadataReader)) {ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);sbd.setSource(resource);if (isCandidateComponent(sbd)) {if (debugEnabled) {logger.debug("Identified candidate component class: " + resource);}candidates.add(sbd);}//################省略其他代码###################catch (IOException ex) {throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);}return candidates;
}

可以看到，在scanCandidateComponents()方法中，会调用isCandidateComponent()方法来判断当前注解是不是要扫描的注解。

17. 解析ClassPathScanningCandidateComponentProvider类的isCandidateComponent(MetadataReader metadataReader)方法

protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {for (TypeFilter tf : this.excludeFilters) {if (tf.match(metadataReader, getMetadataReaderFactory())) {return false;}}for (TypeFilter tf : this.includeFilters) {if (tf.match(metadataReader, getMetadataReaderFactory())) {return isConditionMatch(metadataReader);}}return false;
}

可以看到，isCandidateComponent()方法的逻辑还是比较简单的，就是遍历匹配excludeFilters和includeFilters指定的规则。

优先匹配excludeFilters指定的规则，如果匹配excludeFilters指定的规则，直接返回false。接下来，匹配includeFilters指定的规则，匹配成功，则调用isConditionMatch()方法进行条件匹配。

其中，对于includeFilters而言，默认的过滤规则如下所示：

protected void registerDefaultFilters() {this.includeFilters.add(new AnnotationTypeFilter(Component.class));ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();try {this.includeFilters.add(new AnnotationTypeFilter(((Class) ClassUtils.forName("jakarta.annotation.ManagedBean", cl)), false));logger.trace("JSR-250 'jakarta.annotation.ManagedBean' found and supported for component scanning");}catch (ClassNotFoundException ex) {// JSR-250 1.1 API (as included in Jakarta EE) not available - simply skip.}try {this.includeFilters.add(new AnnotationTypeFilter(((Class) ClassUtils.forName("jakarta.inject.Named", cl)), false));logger.trace("JSR-330 'jakarta.inject.Named' annotation found and supported for component scanning");}catch (ClassNotFoundException ex) {// JSR-330 API not available - simply skip.}
}

可以看到，对于includeFilters而言，默认的过滤规则会匹配@Component注解，JSR-250中的注解和JSR-330中的注解。

18. 回到ClassPathScanningCandidateComponentProvider类的scanCandidateComponents(String basePackage)方法

在ClassPathScanningCandidateComponentProvider类的scanCandidateComponents(String basePackage)方法中，会将标注了@Component注解，JSR-250中的注解和JSR-330中的注解的类信息封装成ScannedGenericBeanDefinition类对象，也就是类的Bean定义信息。

ScannedGenericBeanDefinition类的构造方法如下所示：

public ScannedGenericBeanDefinition(MetadataReader metadataReader) {Assert.notNull(metadataReader, "MetadataReader must not be null");this.metadata = metadataReader.getAnnotationMetadata();setBeanClassName(this.metadata.getClassName());setResource(metadataReader.getResource());
}

19. 回到ClassPathBeanDefinitionScanner类的doScan(String… basePackages)方法

在ClassPathBeanDefinitionScanner类的doScan(String… basePackages)方法中，会将扫描到的类的Bean定义信息注册到IOC容器中，如下代码片段所示：

if (checkCandidate(beanName, candidate)) {BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);definitionHolder =AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);beanDefinitions.add(definitionHolder);registerBeanDefinition(definitionHolder, this.registry);
}

可以看到，在doScan()方法中，会调用registerBeanDefinition()注册Bean定义信息。

20. 解析ClassPathBeanDefinitionScanner类的registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)方法

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

可以看到，在方法中直接调用了BeanDefinitionReaderUtils类的registerBeanDefinition()方法。

21. 解析BeanDefinitionReaderUtils类的registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)方法。

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());//###########省略其他代码###################
}

可以看到，在上述代码中，会继续调用BeanDefinitionRegistry类型的对象registry的registerBeanDefinition()方法，将类的Bean定义信息注册到IOC容器。

22. 解析DefaultListableBeanFactory类的registerBeanDefinition(String beanName, BeanDefinition beanDefinition)方法

@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)throws BeanDefinitionStoreException {//##############省略其他代码#################BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);if (existingDefinition != null) {//##############省略其他代码#################this.beanDefinitionMap.put(beanName, beanDefinition);}else {//##############省略其他代码#################if (hasBeanCreationStarted()) {// Cannot modify startup-time collection elements anymore (for stable iteration)synchronized (this.beanDefinitionMap) {this.beanDefinitionMap.put(beanName, beanDefinition);List updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);updatedDefinitions.addAll(this.beanDefinitionNames);updatedDefinitions.add(beanName);this.beanDefinitionNames = updatedDefinitions;removeManualSingletonName(beanName);}}else {// Still in startup registration phasethis.beanDefinitionMap.put(beanName, beanDefinition);this.beanDefinitionNames.add(beanName);removeManualSingletonName(beanName);}this.frozenBeanDefinitionNames = null;}if (existingDefinition != null || containsSingleton(beanName)) {resetBeanDefinition(beanName);}else if (isConfigurationFrozen()) {clearByTypeCache();}
}

可以看到，Spring会将扫描到的标注了符合过滤规则的注解的类封装成对应的Bean定义信息，最终会将这些Bean定义信息注册到beanDefinitionMap中。这一点和前面章节注册ConfigurationClassPostProcessor类的Bean定义信息有点类似。

好了，至此，@ComponentScans注解与@ComponentScan注解在Spring源码中的执行流程分析完毕。