Spring 容器初始化之 invokeBeanFactoryPostProcessors

Spring容器初始化 refresh() 方法_02

你的贊，是我最大的動力。期待與你們一塊兒，共同進步。

  以前的文章介紹到了，AbstractApplicationContext.refresh()方法，在該方法中有十幾個流程，上一篇文章中介紹了refresh()的前四個流程。這篇文章將重點介紹invokeBeanFactoryPostProcessors(beanFactory)。這個 代碼是重點流程，這篇文章詳細分析一下。

5.invokeBeanFactoryPostProcessors()

5.1 該方法調用流過程

第①步：AbstractApplicationContext#invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory)

第②步：PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

2.1 registryProcessor.postProcessBeanDefinitionRegistry(registry) 處理自定義的 BeanDefinitionRegistryPostProcessor子類
   2.2 DefaultListableBeanFactory.getBeanNamesForType(java.lang.Class<?>, boolean, boolean) 經過type獲得 獲得一個Ben的名稱
複製代碼

第③步：PostProcessorRegistrationDelegate#invokeBeanDefinitionRegistryPostProcessors() spring內部本身實現了BeanDefinitionRegistryPostProcessor接口

第④步：postProcessor.postProcessBeanDefinitionRegistry(registry) 不一樣的子類去本身的實現類中處理，在這裏，spring內部的目前爲止只有一個實現， 那就是ConfigurationClassPostProcessor類，該類是spring內置的。

第⑤步：ConfigurationClassPostProcessor#processConfigBeanDefinitions(),處理 ConfigurationClassPostProcessor

第⑥步：ConfigurationClassUtils.checkConfigurationClassCandidate()

第⑦步：ConfigurationClassParser實例化

第⑧步：ConfigurationClassParser#parse(Set)

注:這裏的parse()方法及其重要，下一篇文章詳細介紹，這裏先看一下前面幾步涉及的代碼邏輯！！！

5.2 invokeBeanFactoryPostProcessors

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
 /**  * getBeanFactoryPostProcessors() 獲取自定義的（咱們本身實現，且沒有交給spring管理的）  */  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())); } 複製代碼

這裏本身定義的 BeanFactoryPostProcessor的實現，是指是這個類的子類，可是沒有交給spring管理，示例以下：

public class TestFactoryPostProcessor implements BeanFactoryPostProcessor {
   @Override  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {  int count = beanFactory.getBeanDefinitionCount();  String[] names = beanFactory.getBeanDefinitionNames();  System.out.println("當前BeanFactory中有"+count+" 個Bean");  System.out.println(Arrays.asList(names));  } } 複製代碼

  這種方式實現的方式，會經過getBeanFactoryPostProcessors()的方式拿到。

5.2.0 時序圖

invokeBeanFactoryPostProcessors時序圖

5.2.1 invokeBeanFactoryPostProcessors

public static void invokeBeanFactoryPostProcessors(  ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {   // Invoke BeanDefinitionRegistryPostProcessors first, if any.  Set<String> processedBeans = new HashSet<>();   /** 對 BeanDefinitionRegistry 類型的處理 */  if (beanFactory instanceof BeanDefinitionRegistry) {  BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;  List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();  /**  * BeanDefinitionRegistryPostProcessor  */  List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();  /**自定義的BeanFactoryPostProcessor*/  for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {  if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {  BeanDefinitionRegistryPostProcessor registryProcessor =  (BeanDefinitionRegistryPostProcessor) postProcessor;  /**  * 對於 BeanDefinitionRegistryPostProcessor 類型，  * 在 BeanFactoryPostProcessor 的基礎上還有本身定義的方法  * 須要先調用  */  registryProcessor.postProcessBeanDefinitionRegistry(registry);  registryProcessors.add(registryProcessor);  }  else {  /**  * 記錄常規的 BeanFactoryPostProcessor  */  regularPostProcessors.add(postProcessor);  }  }   /**  * currentRegistryProcessors是放的spring內部本身實現了BeanDefinitionRegistryPostProcessor接口  */  List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();   // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.  /**  * getBeanNamesForType() 經過type 類型 獲得一個Ben的名稱、type指的是 spring bean 描述文件的class類型  */  String[] postProcessorNames =  beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);  /**  * 這個BeanFactory是spring最開始默認註冊的  */  for (String ppName : postProcessorNames) {  if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {  currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));  processedBeans.add(ppName);  }  }  /**  * 排序  */  sortPostProcessors(currentRegistryProcessors, beanFactory);  /**  * 合併list  */  registryProcessors.addAll(currentRegistryProcessors);  /**  * spring 中 不管是本身定義的 仍是內置的 BeanDefinitionRegistryPostProcessor  * 都在這裏處理完成，好比 {@link ConfigurationClassPostProcessor} 的處理  * 這裏是重要代碼。。。  */  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);  /** 清除list */  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);  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);  currentRegistryProcessors.clear();  }   /**  * 執行 BeanFactoryPostProcessor 的回調  * 這裏執行的是 BeanFactoryPostProcessor 的子類 BeanDefinitionRegistryPostProcessor 的回調方法  *  */  invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);  /**  * 這裏執行的是 BeanFactoryPostProcessor 的 postProcessBeanFactory() 方法  */  invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);  }   else {  // Invoke factory processors registered with the context instance.  invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);  }   // Do not initialize FactoryBeans here: We need to leave all regular beans  // uninitialized to let the bean factory post-processors apply to them!  String[] postProcessorNames =  beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);   // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,  // Ordered, and the rest.  List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();  List<String> orderedPostProcessorNames = new ArrayList<>();  List<String> nonOrderedPostProcessorNames = new ArrayList<>();  for (String ppName : postProcessorNames) {  if (processedBeans.contains(ppName)) {  // skip - already processed in first phase above  }  else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {  priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));  }  else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {  orderedPostProcessorNames.add(ppName);  }  else {  nonOrderedPostProcessorNames.add(ppName);  }  }   // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.  sortPostProcessors(priorityOrderedPostProcessors, beanFactory);  invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);   // Next, invoke the BeanFactoryPostProcessors that implement Ordered.  List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();  for (String postProcessorName : orderedPostProcessorNames) {  orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));  }  sortPostProcessors(orderedPostProcessors, beanFactory);  invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);   // Finally, invoke all other BeanFactoryPostProcessors.  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(); } 複製代碼

5.2.2 invokeBeanDefinitionRegistryPostProcessors

private static void invokeBeanDefinitionRegistryPostProcessors(  Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {   /**  * 循環全部的 BeanDefinitionRegistryPostProcessor  */  for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {  /**  * 根據不一樣的 BeanDefinitionRegistryPostProcessors 實現  * 去調用不一樣的 postProcessBeanDefinitionRegistry 方法  */  postProcessor.postProcessBeanDefinitionRegistry(registry);  } } 複製代碼

  經過上述方法，可只在Spring 中先處理程序員本身定義的 BeanFactoryPostProcessor，而後在處理Spring中內置的，後者說交給其管理的 BeanDefinitionRegistryPostProcessor，其中 BeanDefinitionRegistryPostProcessor 是 BeanFactoryPostProcessor 的子類。截止到目前爲止 Spring 中惟一的一個內置的 BeanDefinitionRegistryPostProcessor 的實現類就是 ConfigurationClassPostProcessor 接下來就是對 ConfigurationClassPostProcessor 的處理。

5.3 ConfigurationClassPostProcessor 的處理

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);  /**  * 處理 ConfigurationClassPostProcessor  */  processConfigBeanDefinitions(registry); } 複製代碼

  對 ConfigurationClassPostProcessor 的真正的處理是經過 processConfigBeanDefinitions 來完成的

5.3.1 processConfigBeanDefinitions

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
 /** 存放spring 中 bean的描述文件*/  List<BeanDefinitionHolder> configCandidates = new ArrayList<>();  /** 獲取容器中全部註冊bean的名字*/  String[] candidateNames = registry.getBeanDefinitionNames();   for (String beanName : candidateNames) {  /** 根據beanName 獲取bean的描述文件 */  BeanDefinition beanDef = registry.getBeanDefinition(beanName);  if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||  ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {  if (logger.isDebugEnabled()) {  logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);  }  }  /**  * 判斷是不是Configuration類 是否包含 @Configuration 註解  * checkConfigurationClassCandidate(）注意這個方法  */  else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {  /** 這裏若是添加了 @Configuration  * 將該類封裝成BeanDefinitionHolder 放入到 configCandidates  * 後面解析會用到  */  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  configCandidates.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 context  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) {  this.componentScanBeanNameGenerator = generator;  this.importBeanNameGenerator = generator;  }  }  }   if (this.environment == null) {  this.environment = new StandardEnvironment();  }   // Parse each @Configuration class  /** 實例化 ConfigurationClassParser 解析各個配置*/  ConfigurationClassParser parser = new ConfigurationClassParser(  this.metadataReaderFactory, this.problemReporter, this.environment,  this.resourceLoader, this.componentScanBeanNameGenerator, registry);  /**  * 實例化兩個Set candidates用於將以前加入的configCandidates 進行去重  * 由於可能有多個配置類重複了  * alreadyParsed 用於判斷是否處理過  */  Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);   Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());  do {  /**  * 解析註解類，  * 這裏是重點代碼  */  parser.parse(candidates);   parser.validate();   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());  }  /**  * loadBeanDefinitions() 中處理 @Import 的類  */  this.reader.loadBeanDefinitions(configClasses);  alreadyParsed.addAll(configClasses);   candidates.clear();  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());  }  for (String candidateName : newCandidateNames) {  if (!oldCandidateNames.contains(candidateName)) {  BeanDefinition bd = registry.getBeanDefinition(candidateName);  if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&  !alreadyParsedClasses.contains(bd.getBeanClassName())) {  candidates.add(new BeanDefinitionHolder(bd, candidateName));  }  }  }  candidateNames = newCandidateNames;  }  }  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();  } } 複製代碼

5.3.2 對於 beanDef 的判斷

  對於 beanDef 判斷的代碼片斷以下：

BeanDefinition beanDef = registry.getBeanDefinition(beanName);
if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||  ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {  if (logger.isDebugEnabled()) {  logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);  } } 複製代碼

  在 ConfigurationClassUtils 中定義了兩個常量用 private static final String CONFIGURATION_CLASS_FULL = "full" 和 private static final String CONFIGURATION_CLASS_LITE = "lite" 使用這兩個常量用來判斷當前的 BeanDefinition 是一個 全配置類仍是 部分配置類。在這裏對於 @Configuration 註解的配置裏走下面的 checkConfigurationClassCandidate 判斷，可斷點調試驗證。

5.3.3 checkConfigurationClassCandidate

public static boolean checkConfigurationClassCandidate(  BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {   String className = beanDef.getBeanClassName();  if (className == null || beanDef.getFactoryMethodName() != null) {  return false;  }   AnnotationMetadata metadata;  if (beanDef instanceof AnnotatedBeanDefinition &&  className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {  /**  * 若是 beanDefinition 是 AnnotatedBeanDefinition的實例  * 而且 className 和 beanDefinition 中的元數據類名相同  * 從 AnnotatedBeanDefinition 中獲取 元數據  */  // Can reuse the pre-parsed metadata from the given BeanDefinition...  metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();  }  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.  /**  * 若是 beanDefinition 是 AbstractBeanDefinition 的實例  * 而且 beanDefinition 有 beanClass屬性存在  * 實例化 StandardAnnotationMetadata  */  Class<?> beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();  metadata = new StandardAnnotationMetadata(beanClass, true);  }  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;  }  }  /** 判斷元數據 是否加了 @Configuration 註解*/  if (isFullConfigurationCandidate(metadata)) {  /**  * 若是存在 @Configuration 註解，beanDefinition 中設置 configurationClass 爲 full  * spring 認爲該類是一個全註解的類  */  beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);  }  /**  * 判斷是否加了 @Import，@Component  * @ImportResource, @ComponentScan 註解  */  else if (isLiteConfigurationCandidate(metadata)) {  /**  * 若是不存在 @Configuration 註解，beanDefinition 中設置 configurationClass 爲 lite  * spring 認爲該類是一個部分註解類  */  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; } 複製代碼

  在 checkConfigurationClassCandidate 方法中 @Configuration 註解是的類是 AnnotatedBeanDefinition的實現，首先獲取到元數據 metadata 以下圖：   而後，對於加了 @Configuration註解的類，會將該類的屬性設置爲 full，以下圖：   最後，若是 checkConfigurationClassCandidate() 方法返回true，而後將 BeanDefinition 封裝成 BeanDefinitionHolder 添加到 configCandidates 中，供後面解析使用。

5.4 ConfigurationClassParser 實例化

ConfigurationClassParser parser = new ConfigurationClassParser(
 this.metadataReaderFactory, this.problemReporter, this.environment,  this.resourceLoader, this.componentScanBeanNameGenerator, registry); 複製代碼

容器造成圖

  在本文章中並無在 IoC容器中添加新的對象。這篇文章中涉及到的就是對@Configuration註解類對應的Spring內置的ConfigurationClassPostProcessor處理。

本文使用 mdnice 排版