『SpringBoot 源码分析』run() 方法执行流程：（3）刷新应用上下文-处理 @ComponentScan 注解

• 基于 2.2.9.RELEASE
• 问题：当方法进行了注释标记之后，springboot 又是怎么注入到容器中并创建类呢？

1. 首先创建测试主程序

package com.lagou;@SpringBootApplication//标注在类上说明这个类是`SpringBoot`的主配置类
public class SpringBootMytestApplication{public static void main(String[] args) {SpringApplication.run(SpringBootMytestApplication.class, args);}
}

2. 创建测试 Controller

package com.lagou.controller;@RestController
public class TestController {@RequestMapping("/test")public String test(){System.out.println("源码环境构建成功...");return "源码环境构建成功";}
}

处理 @ComponentScan 注解

1. 准备好上下文以及上下文环境之后，可以继续来看看 springboot 究竟是如何把主类所在的类路径下相关的类通过 @ComponentScan 注册到 IOC 容器中。首先先走到 refreshContext() 方法，然后调用 ApplicationContext 的 refresh()

public class SpringApplication {...public ConfigurableApplicationContext run(String... args) {...try {// 将运行时参数封装ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);// 构造应用上下文环境ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);// 处理需要忽略的 BeanconfigureIgnoreBeanInfo(environment);// 打印 bannerBanner printedBanner = printBanner(environment);// 刷新应用上下文前的准备阶段context = createApplicationContext();// 实例化 SpringBootExceptionReporter.class，用来支持报告关于启动的错误exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,new Class[] { ConfigurableApplicationContext.class }, context);// 刷新应用上下文前的准备阶段prepareContext(context, environment, listeners, applicationArguments, printedBanner);// 1. 刷新应用上下文refreshContext(context);...}catch (Throwable ex) {...}...}protected void refresh(ApplicationContext applicationContext) {Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);// 2. spring 的核心方法，刷新上下文((AbstractApplicationContext) applicationContext).refresh();}
}

2. 接着 ApplicationContext 调用父类的 refresh()

public class ServletWebServerApplicationContext extends GenericWebApplicationContextimplements ConfigurableWebServerApplicationContext {...@Overridepublic final void refresh() throws BeansException, IllegalStateException {try {// 1. 调用父类 refresh() 方法super.refresh();}catch (RuntimeException ex) {stopAndReleaseWebServer();throw ex;}}
}

3. 在 refresh() 中，首先对上下文进行预处理，设置一些必要的参数，然后获取 IOC 容器，并对 IOC 容器进行一些参数进行设置，然后调用工厂处理器注册相关的 bean 进入上下文

public abstract class AbstractApplicationContext extends DefaultResourceLoaderimplements ConfigurableApplicationContext {private final Object startupShutdownMonitor = new Object();...@Overridepublic void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {// 1. 上下文设置一些必要的参数prepareRefresh();// 2. 获取 IOC 容器ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();// 3. 对 IOC 容器进行一些参数设置prepareBeanFactory(beanFactory);try {// Allows post-processing of the bean factory in context subclasses.postProcessBeanFactory(beanFactory);// 4. 调用工厂处理器，注册 bean 到 IOC 容器invokeBeanFactoryPostProcessors(beanFactory);...} catch (BeansException ex) {...}...}}protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {// 5. 对 IOC 容器调用 beanFactoryPostProcessors 来处理  		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()));}}
}

4. 通过后置处理器注册的委派类 PostProcessorRegistrationDelegate 调用 invokeBeanFactoryPostProcessors() 的逻辑相对复杂一些，我们直接跳过，只关注问题本身，走到下面的一句话

final class PostProcessorRegistrationDelegate {...public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {// Invoke BeanDefinitionRegistryPostProcessors first, if any.Set<String> processedBeans = new HashSet<>();if (beanFactory instanceof BeanDefinitionRegistry) {BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {BeanDefinitionRegistryPostProcessor registryProcessor =(BeanDefinitionRegistryPostProcessor) postProcessor;registryProcessor.postProcessBeanDefinitionRegistry(registry);registryProcessors.add(registryProcessor);}else {regularPostProcessors.add(postProcessor);}}// Do not initialize FactoryBeans here: We need to leave all regular beans// uninitialized to let the bean factory post-processors apply to them!// Separate between BeanDefinitionRegistryPostProcessors that implement// PriorityOrdered, Ordered, and the rest.List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.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);// 1. 调用 bean 注册处理器，处理类的注册			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);...}...}private static void invokeBeanDefinitionRegistryPostProcessors(Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {// 2. 其中 postProcessors 只有一个类，即为	ConfigurationClassPostProcessor 		postProcessor.postProcessBeanDefinitionRegistry(registry);}}
}

• 其中，配置类最关键的对象是 ConfigurationClassPostProcessor 后置处理器
  

5. 这时候就会交由 ConfigurationClassPostProcessor 来注册 bean 到 IOC 容器中

public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {private final Set<Integer> registriesPostProcessed = new HashSet<>();...@Overridepublic 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);// 1. 注册 bean 到 IOC 容器中processConfigBeanDefinitions(registry);}
}

6. 当调用 processConfigBeanDefinitions() 时，首先会创建 ConfigurationClassParser 用于解析 @Configuration

public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {private MetadataReaderFactory metadataReaderFactory = new CachingMetadataReaderFactory();private ProblemReporter problemReporter = new FailFastProblemReporter();@Nullableprivate Environment environment;private ResourceLoader resourceLoader = new DefaultResourceLoader();private BeanNameGenerator componentScanBeanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;...public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {List<BeanDefinitionHolder> configCandidates = new ArrayList<>();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);}}// 把主类封装进 BeanDefinitionHolder 中else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));}}// Return immediately if no @Configuration classes were foundif (configCandidates.isEmpty()) {return;}// Sort by previously determined @Order value, if applicableconfigCandidates.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 contextSingletonBeanRegistry 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();}// 1. 创建解析器，用于解析 @Configuration 标注的类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 {// 2. 开始解析候选类parser.parse(candidates);...}while (!candidates.isEmpty());...}
}

• 其中，这里的 candidates 属性也就只有主类
  

7. 接下来会遍历 candidates 属性，解析主类的注解

class ConfigurationClassParser {private static final Predicate<String> DEFAULT_EXCLUSION_FILTER = className ->(className.startsWith("java.lang.annotation.") || className.startsWith("org.springframework.stereotype."));...public void parse(Set<BeanDefinitionHolder> configCandidates) {for (BeanDefinitionHolder holder : configCandidates) {BeanDefinition bd = holder.getBeanDefinition();try {if (bd instanceof AnnotatedBeanDefinition) {// 1. 解析主类配置，其中 getBeanName() 为 SpringBootMytestApplicationparse(((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();}protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {processConfigurationClass(new ConfigurationClass(metadata, beanName), DEFAULT_EXCLUSION_FILTER);}
}

8. 再走进一层嵌套中，遇到 do 开头的方法，才是真正处理的时候

class ConfigurationClassParser {...protected void processConfigurationClass(ConfigurationClass configClass, Predicate<String> filter) throws IOException {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);}}// Recursively process the configuration class and its superclass hierarchy.SourceClass sourceClass = asSourceClass(configClass, filter);do {// 1. 真正处理 @Configuration 的方法，其中 sourceClass 为 com.lagou.SpringBootMytestApplicationsourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);}while (sourceClass != null);this.configurationClasses.put(configClass, configClass);}
}

9. 接下来会根据不同的注解，执行不同的处理方法，这里主要关注处理 @ComponentScan 注解的位置，首先会判断 sourceClass 是否标注了 @ComponentScan 注解，主类 @SpringBootApplication 是肯定包含这个注解。然后通过 ComponentScanAnnotationParser 来进行解析

class ConfigurationClassParser {private final ComponentScanAnnotationParser componentScanParser;private final ConditionEvaluator conditionEvaluator;private final Environment environment;...@Nullableprotected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)throws IOException {if (configClass.getMetadata().isAnnotated(Component.class.getName())) {// Recursively process any member (nested) classes firstprocessMemberClasses(configClass, sourceClass, filter);}// Process any @PropertySource annotationsfor (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");}}// 1. 扫描主类 @ComponentScan 注解里面的配置属性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) {// 2. 解析 @ComponentScan 的注解的属性，然后把扫描到的相关类转化为 BeanDefinitionSet<BeanDefinitionHolder> 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());}}}}...}
}

10. parse() 主体逻辑就是首先创建 ClassPathBeanDefinitionScanner 扫描器，然后判断主类的 @ComponentScan 注解是否标注了 basePackages 属性，没有的话就把主类所在的包放进去，然后扫描所有的 @Component 类，封装成 BeanDefinition

• 重点：所以这里就是为什么主类所在的包，以及其子包的类都能扫出来

class ComponentScanAnnotationParser {private final BeanNameGenerator beanNameGenerator;private final ResourceLoader resourceLoader;private final Environment environment;private final BeanDefinitionRegistry registry;...// declaringClass 为 com.lagou.SpringBootMytestApplicationpublic Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {// 1. 创建 BeanDefinition 扫描器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));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"));for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {for (TypeFilter typeFilter : typeFiltersFor(filter)) {scanner.addIncludeFilter(typeFilter);}}for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {for (TypeFilter typeFilter : typeFiltersFor(filter)) {scanner.addExcludeFilter(typeFilter);}}boolean lazyInit = componentScan.getBoolean("lazyInit");if (lazyInit) {scanner.getBeanDefinitionDefaults().setLazyInit(true);}Set<String> basePackages = new LinkedHashSet<>();// 2. 尝试查看注解有没添加 basePackages 属性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()) {// 3. 没有就获取类所在的包名，这里是 com.lagou			basePackages.add(ClassUtils.getPackageName(declaringClass));}scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {@Overrideprotected boolean matchClassName(String className) {return declaringClass.equals(className);}});// 4. 扫描对应的包，把所有相关的 @Component 的类封装成 BeanDefinition 返回return scanner.doScan(StringUtils.toStringArray(basePackages));}
}

• 其中，componentScan 包含的相关属性如下
  

11. doScan() 先通过 basePackages 属性，找到所有候选 Components，然后把它们注册到 IOC 容器中并返回

public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {private final BeanDefinitionRegistry registry;private BeanNameGenerator beanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;private ScopeMetadataResolver scopeMetadataResolver = new AnnotationScopeMetadataResolver();...protected Set<BeanDefinitionHolder> doScan(String... basePackages) {// 1. basePackages 为 com.lagouAssert.notEmpty(basePackages, "At least one base package must be specified");Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();for (String basePackage : basePackages) {// 2. 根据 basePackage 找到所有候选的 ComponentsSet<BeanDefinition> 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);// 3. 将候选 Components 注册进 IOC 容器registerBeanDefinition(definitionHolder, this.registry);}}}// 4. 返回 beanDefinitionsreturn beanDefinitions;}
}

• 其中，findCandidateComponents() 会调用嵌套方法 scanCandidateComponents()。它会把 basePackage 属性拼接起来，形成 classpath*:com/lagou/**/*.class 路径，扫描所有的类，并返回

public class ClassPathScanningCandidateComponentProvider implements EnvironmentCapable, ResourceLoaderAware {static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";private String resourcePattern = DEFAULT_RESOURCE_PATTERN;...private Set<BeanDefinition> scanCandidateComponents(String basePackage) {Set<BeanDefinition> candidates = new LinkedHashSet<>();try {// 1. 拼接的路径为 classpath*:com/lagou/**/*.classString packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +resolveBasePackage(basePackage) + '/' + this.resourcePattern;// 2. 得到已经扫描出来的源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 {MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource);// 先判断 resource 是不是候选的 componentif (isCandidateComponent(metadataReader)) {//  封装成通用 BeanDefinitionScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);sbd.setSource(resource);if (isCandidateComponent(sbd)) {if (debugEnabled) {logger.debug("Identified candidate component class: " + resource);}candidates.add(sbd);}else {if (debugEnabled) {logger.debug("Ignored because not a concrete top-level class: " + resource);}}}else {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);}// 3. 返回所有扫描出来的候选 componentsreturn candidates;
}

• （续）
  • 扫描出来的 resources 属性如下
    
• （续）
  • 最后的候选 components 属性（只有 com.lagou.config.MyDataSourceConfig 与 com.lagou.controller.TestController）如下
    
• 其中，registerBeanDefinition() 会调用 BeanDefinitionReaderUtils 来注册扫描出来的类

public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {...protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {// 1. 注册扫描出来的类。这里先注册 com.lagou.config.MyDataSourceConfig，后注册 com.lagou.controller.TestControllerBeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);}
}

• （续）
  • BeanDefinitionReaderUtils 又会通过 BeanDefinitionRegistry （其实就是我们一开始创建的上下文转换强转过来的）调用 registerBeanDefinition() 方法进行注册

public abstract class BeanDefinitionReaderUtils {...public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)throws BeanDefinitionStoreException {// Register bean definition under primary name.String beanName = definitionHolder.getBeanName();// 1. 通过 BeanDefinitionRegistry 注册扫描出来的类，这里是先注册 com.lagou.config.MyDataSourceConfig，后注册 com.lagou.controller.TestControllerregistry.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);}}}
}

• （续）
  • 最后会把这些扫描出来的类，放到 beanDefinitionMap 属性中

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactoryimplements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {/** List of bean definition names, in registration order. */private volatile List<String> beanDefinitionNames = new ArrayList<>(256);/** Map of bean definition objects, keyed by bean name. */private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);...@Overridepublic void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)throws BeanDefinitionStoreException {Assert.hasText(beanName, "Bean name must not be empty");Assert.notNull(beanDefinition, "BeanDefinition must not be null");if (beanDefinition instanceof AbstractBeanDefinition) {try {((AbstractBeanDefinition) beanDefinition).validate();}catch (BeanDefinitionValidationException ex) {throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,"Validation of bean definition failed", ex);}}BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);if (existingDefinition != null) {if (!isAllowBeanDefinitionOverriding()) {throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);}else if (existingDefinition.getRole() < beanDefinition.getRole()) {// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTUREif (logger.isInfoEnabled()) {logger.info("Overriding user-defined bean definition for bean '" + beanName +"' with a framework-generated bean definition: replacing [" +existingDefinition + "] with [" + beanDefinition + "]");}}else if (!beanDefinition.equals(existingDefinition)) {if (logger.isDebugEnabled()) {logger.debug("Overriding bean definition for bean '" + beanName +"' with a different definition: replacing [" + existingDefinition +"] with [" + beanDefinition + "]");}}else {if (logger.isTraceEnabled()) {logger.trace("Overriding bean definition for bean '" + beanName +"' with an equivalent definition: replacing [" + existingDefinition +"] with [" + beanDefinition + "]");}}this.beanDefinitionMap.put(beanName, beanDefinition);}else {if (hasBeanCreationStarted()) {// Cannot modify startup-time collection elements anymore (for stable iteration)synchronized (this.beanDefinitionMap) {// 1. 把对应的 beanDefinition 注册到 beanDefinitionMap 中this.beanDefinitionMap.put(beanName, beanDefinition);List<String> 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();}}
}

12. 返回完 ComponentScans 注解扫描的类之后，会判断候选类是不是有 @Configuration 标记，有的话，会继续深度调用 processConfigurationClass()，继续扫描所有候选类，注册进 beanDefinitionMap 中

class ConfigurationClassParser {private final ComponentScanAnnotationParser componentScanParser;private final ConditionEvaluator conditionEvaluator;private final Environment environment;...@Nullableprotected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)throws IOException {if (configClass.getMetadata().isAnnotated(Component.class.getName())) {// Recursively process any member (nested) classes firstprocessMemberClasses(configClass, sourceClass, filter);}// Process any @PropertySource annotationsfor (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");}}// 扫描处理所有 @ComponentScan 注解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) {// 解析 @ComponentScan 的注解，然后把相关对象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 neededfor (BeanDefinitionHolder holder : scannedBeanDefinitions) {BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();if (bdCand == null) {bdCand = holder.getBeanDefinition();}// 1. 判断扫描的类是不是用  @Configuration 标记if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {// 2. 是的话继续解析该配置类 parse(bdCand.getBeanClassName(), holder.getBeanName());}}}}...}protected final void parse(@Nullable String className, String beanName) throws IOException {Assert.notNull(className, "No bean class name for configuration class bean definition");MetadataReader reader = this.metadataReaderFactory.getMetadataReader(className);// 3. 形成递归调用解析processConfigurationClass(new ConfigurationClass(reader, beanName), DEFAULT_EXCLUSION_FILTER);}
}

13. 直到这里我们就能够明白如何把主类所在的类路径下相关的类通过 @ComponentScan 注册到 IOC 容器中，像相关的 @Import、@ImportResource 注册，也是在 processConfigurationClass() 这个方法里解析，下节再解析
14. 总结