Spring IoC源码解析之invokeBeanFactoryPostProcessors

一、Bean工厂的后置处理器

　　Bean工厂的后置处理器：BeanFactoryPostProcessor（触发时机：bean定义注册之后bean实例化之前）和BeanDefinitionRegistryPostProcessor（触发时机：bean定义注册之前），所以可以在Bean工厂的后置处理器中修改Bean的定义信息，比如是否延迟加载、加入一些新的Bean的定义信息等

　　Bean工厂的后置处理器类继承图：

二、调用Bean工厂的后置处理器

　　invokeBeanFactoryPostProcessors(beanFactory)方法：

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());

// 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()));
}
}

　　进入PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())方法：

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

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();
}

　　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)  Debug进去看到如下：为什么就一个ConfigurationClassPostProcessor，因为我们自定的BeanDefinitionRegistryPostProcessor还没有被加入到Spring容器中去

　　第一步里面的invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法：

/**
* Invoke the given BeanDefinitionRegistryPostProcessor beans.
*/
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
//获取容器中的ConfigurationClassPostProcessor的后置处理器进行Bean定义的扫描
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}

　　接下来就会调用到org.springframework.context.annotation.ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry方法（很重要）：

/**
* Derive further bean definitions from the configuration classes in the registry.
*/
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
int registryId = System.identityHashCode(registry);
if (this.registriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
}
if (this.factoriesPostProcessed.contains(registryId)) {
throw new IllegalStateException(
"postProcessBeanFactory already called on this post-processor against " + registry);
}
this.registriesPostProcessed.add(registryId);
//真正的解析我们的Bean定义
processConfigBeanDefinitions(registry);
}

　　进入到真正的解析processConfigBeanDefinitions方法中：

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
else if (ConfigurationClassUtils.checkConfigurationClassCandidate(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) {
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 while
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)) {
BeanDefinition bd = registry.getBeanDefinition(candidateName);
//判断有没有被解析过
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();
}
}

　　Debug解析：

　　进入parser.parse(candidates)方法：

public void parse(Set<BeanDefinitionHolder> configCandidates) {
//用于保存延时的ImportSelectors
this.deferredImportSelectors = new LinkedList<>();

for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
//真正的解析我们的bean定义
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);
}
}
//处理我们延时的DeferredImportSelectors Spring Boot就是通过这步进行spring.factories文件中的自定装配的对象
processDeferredImportSelectors();
}

　　Debug解析:

　　进入parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName())方法：

/**
* 真正的解析我们的配置类
* @param metadata 配置类的源信息
* @param beanName 当前配置类的beanName
* @throws IOException
*/
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));
}

　　进入processConfigurationClass(new ConfigurationClass(metadata, beanName))方法：

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);

if (existingClass != null) {
//传入的配置类是通过其他配置类的Import导入进来的
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);
}
}

// Recursively process the configuration class and its superclass hierarchy.
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);

this.configurationClasses.put(configClass, configClass);
}

　　进入解析我们的配置类的doProcessConfigurationClass(configClass, sourceClass)方法：

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

// Recursively process any member (nested) classes first
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.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}

//接下来解析我们的@ComponentScans注解
//从我们的配置类上解析@ComponentScans的对象集合属性
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) {
//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());
//循环处理我们包扫描出来的bean定义
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
processImports(configClass, sourceClass, getImports(sourceClass), true);

//处理@ImportResource
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;
}

　　Debug解析：

　　① 解析@ComponentScanthis.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName())方法：

public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);

//给扫描器设置beanName的生成器对象
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));
}

　　进入真正的进行扫描解析scanner.doScan(StringUtils.toStringArray(basePackages))方法：

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) {
//找到候选的@Component
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {

ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
//设置我们的beanName
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
//处理@AutoWired相关的
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
//处理jsr250相关的组件
if (candidate instanceof AnnotatedBeanDefinition) {
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);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//注册到Spring IoC容器中
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}

　　Debug解析：

　　进过org.springframework.context.annotation.ClassPathBeanDefinitionScanner#doScan处理，Spring IoC容器中Bean的定义有12个了；

　　② 接下来处理@Import注解导入的Bean组件：

　　进入处理@Import注解的processImports(configClass, sourceClass, getImports(sourceClass), true)方法：

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
Collection<SourceClass> importCandidates, boolean checkForCircularImports) {

if (importCandidates.isEmpty()) {
return;
}

if (checkForCircularImports && isChainedImportOnStack(configClass)) {
this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
}
else {
this.importStack.push(configClass);
try {
//获取我们Import导入进来的所有组件
for (SourceClass candidate : importCandidates) {
//判断该组件是不是实现了ImportSelector的
if (candidate.isAssignable(ImportSelector.class)) {
// Candidate class is an ImportSelector -> delegate to it to determine imports
Class<?> candidateClass = candidate.loadClass();
//实例化我们的SelectImport组件
ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
//调用相关的aware方法
ParserStrategyUtils.invokeAwareMethods(
selector, this.environment, this.resourceLoader, this.registry);
//判断是不是延时的DeferredImportSelectors，是这个类型不进行处理
if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
this.deferredImportSelectors.add(
new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
}
else {//不是延时的调用selector的selectImports
String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
//反之SelectImport导入进来的又是Import进来的 所以递归解析
Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
processImports(configClass, currentSourceClass, importSourceClasses, false);
}
}
//判断我们导入的组件是不是ImportBeanDefinitionRegistrar
else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
// Candidate class is an ImportBeanDefinitionRegistrar ->
// delegate to it to register additional bean definitions
Class<?> candidateClass = candidate.loadClass();
//实例话我们的ImportBeanDefinitionRegistrar对象
ImportBeanDefinitionRegistrar registrar =
BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
ParserStrategyUtils.invokeAwareMethods(
registrar, this.environment, this.resourceLoader, this.registry);
//保存我们的ImportBeanDefinitionRegistrar对象
configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
}
else {//就是一个普通的组件  但是防止我们普通的组件是一个配置类 所以还是直接走了processConfigurationClass()方法
this.importStack.registerImport(
currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
processConfigurationClass(candidate.asConfigClass(configClass));
}
}
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process import candidates for configuration class [" +
configClass.getMetadata().getClassName() + "]", ex);
}
finally {
this.importStack.pop();
}
}
}

 　　③ 接下来处理@ImportSource比如@ImportResource("classpath:circulation-di.xml")，基于xml的（略）

　　 ④ 接下来处理@Bean：

　　至此解析完成，注意@Import、@ImportSource、@Bean的定义还未注册到Spring IoC的容器中去

　　接下来将剩余的Bean定义信息注册到Spring IoC容器中：

 　　进入真正的把我们解析出来的配置类注册到容器中this.reader.loadBeanDefinitions(configClasses)方法：

public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
//注册我们的配置类到容器中
for (ConfigurationClass configClass : configurationModel) {
loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
}
}

　　进入loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator)方法：

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;
}

//是不是通过@Import导入进来的
if (configClass.isImported()) {
registerBeanDefinitionForImportedConfigurationClass(configClass);
}
//是不是通过我们的@Bean导入进来的组件
for (BeanMethod beanMethod : configClass.getBeanMethods()) {
loadBeanDefinitionsForBeanMethod(beanMethod);
}

//是不是通过@ImportResources导入进来的
loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
//是不是通过ImportBeanDefinition注解导入进来的
loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
}

　　① 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 + "'");
}
}

 　　② 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();

// Do we need to mark the bean as skipped by its condition?
if (this.conditionEvaluator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
configClass.skippedBeanMethods.add(methodName);
return;
}
if (configClass.skippedBeanMethods.contains(methodName)) {
return;
}

AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
Assert.state(bean != null, "No @Bean annotation attributes");

// Consider name and any aliases
List<String> names = new ArrayList<>(Arrays.asList(bean.getStringArray("name")));
String beanName = (!names.isEmpty() ? names.remove(0) : methodName);

// Register aliases even when overridden
for (String alias : names) {
this.registry.registerAlias(beanName, alias);
}

// Has this effectively been overridden before (e.g. via XML)?
if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
if (beanName.equals(beanMethod.getConfigurationClass().getBeanName())) {
throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
beanName, "Bean name derived from @Bean method '" + beanMethod.getMetadata().getMethodName() +
"' clashes with bean name for containing configuration class; please make those names unique!");
}
return;
}

ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata);
beanDef.setResource(configClass.getResource());
beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));

if (metadata.isStatic()) {
// static @Bean method
beanDef.setBeanClassName(configClass.getMetadata().getClassName());
beanDef.setFactoryMethodName(methodName);
}
else {
// instance @Bean method
beanDef.setFactoryBeanName(configClass.getBeanName());
beanDef.setUniqueFactoryMethodName(methodName);
}
beanDef.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
beanDef.setAttribute(RequiredAnnotationBeanPostProcessor.SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);

AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);

Autowire autowire = bean.getEnum("autowire");
if (autowire.isAutowire()) {
beanDef.setAutowireMode(autowire.value());
}

String initMethodName = bean.getString("initMethod");
if (StringUtils.hasText(initMethodName)) {
beanDef.setInitMethodName(initMethodName);
}

String destroyMethodName = bean.getString("destroyMethod");
beanDef.setDestroyMethodName(destroyMethodName);

// Consider scoping
ScopedProxyMode proxyMode = ScopedProxyMode.NO;
AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(metadata, Scope.class);
if (attributes != null) {
beanDef.setScope(attributes.getString("value"));
proxyMode = attributes.getEnum("proxyMode");
if (proxyMode == ScopedProxyMode.DEFAULT) {
proxyMode = ScopedProxyMode.NO;
}
}

// Replace the original bean definition with the target one, if necessary
BeanDefinition beanDefToRegister = beanDef;
if (proxyMode != ScopedProxyMode.NO) {
BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
new BeanDefinitionHolder(beanDef, beanName), this.registry,
proxyMode == ScopedProxyMode.TARGET_CLASS);
beanDefToRegister = new ConfigurationClassBeanDefinition(
(RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata);
}

if (logger.isDebugEnabled()) {
logger.debug(String.format("Registering bean definition for @Bean method %s.%s()",
configClass.getMetadata().getClassName(), beanName));
}
this.registry.registerBeanDefinition(beanName, beanDefToRegister);
}

　　③ 通过@ImportResources导入进来的执行loadBeanDefinitionsFromImportedResources(configClass.getImportedResources())方法：

private void loadBeanDefinitionsFromImportedResources(
Map<String, Class<? extends BeanDefinitionReader>> importedResources) {

Map<Class<?>, BeanDefinitionReader> readerInstanceCache = new HashMap<>();

importedResources.forEach((resource, readerClass) -> {
// Default reader selection necessary?
if (BeanDefinitionReader.class == readerClass) {
if (StringUtils.endsWithIgnoreCase(resource, ".groovy")) {
// When clearly asking for Groovy, that's what they'll get...
readerClass = GroovyBeanDefinitionReader.class;
}
else {
// Primarily ".xml" files but for any other extension as well
readerClass = XmlBeanDefinitionReader.class;
}
}

BeanDefinitionReader reader = readerInstanceCache.get(readerClass);
if (reader == null) {
try {
// Instantiate the specified BeanDefinitionReader
reader = readerClass.getConstructor(BeanDefinitionRegistry.class).newInstance(this.registry);
// Delegate the current ResourceLoader to it if possible
if (reader instanceof AbstractBeanDefinitionReader) {
AbstractBeanDefinitionReader abdr = ((AbstractBeanDefinitionReader) reader);
abdr.setResourceLoader(this.resourceLoader);
abdr.setEnvironment(this.environment);
}
readerInstanceCache.put(readerClass, reader);
}
catch (Throwable ex) {
throw new IllegalStateException(
"Could not instantiate BeanDefinitionReader class [" + readerClass.getName() + "]");
}
}

// TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
reader.loadBeanDefinitions(resource);
});
}

　　④ 通过ImportBeanDefinition注解导入进来的执行loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars())方法：

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

 　　至此第一步里面的invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法执行完毕！！！！

　　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) 此时就有了自己定义的BeanDefinitionRegistryPostProcessor了，接下来调用自定义的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry后置方法，然后再调用postProcessBeanFactory原因是BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor；

　　最后一步：获取容器中所有的BeanFactoryPostProcessor的名称 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false) 此时就有了自己定义的BeanFactoryPostProcessor了，接下来调用自定义的BeanFactoryPostProcessor的postProcessBeanFactory方法；

　　完整的Spring IoC源码解析见：Spring系列（三）：Spring IoC源码解析

三、Spring IoC扫描Bean的流程图

　　总结：通过调用我们的Bean工厂的后置处理器，第一步：ConfigurationClassPostProcessor，解析我们的配置类，将所有的Bean的定义信息注册到Spring IoC容器中；第二步调用自定义的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry后置方法，然后再调用postProcessBeanFactory；最后调用自定义的BeanFactoryPostProcessor的postProcessBeanFactory方法