关于java:spring-解析-Configuration-流程

spring 的 ConfigurationClassPostProcessor 次要是解析 @Configuration 类，通常只有一个入口类，对他进行递归解析，解析完所有关联类，包含应用 Configuration、Component、ComponentScan、Import、ImportResource、Bean 注解关联的类，将其注册进BeanFactory 中。

ConfigurationClassPostProcessor 类的结构图如下：

在创立容器SpringApplication#createApplicationContext 时将ConfigurationClassPostProcessor 注册进 ApplicationContext 中。

他实现了 BeanDefinitionRegistryPostProcessor，将在 AbstractApplicationContext#refresh 中将在 BeanFactory 筹备好之后执行。

/**
 * Derive further bean definitions from the configuration classes in the registry.
 * 从派生类中注册更多的 bean
 */
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    // 生成 ID，如果蕴含则阐明该 BeanFactoryProcess 曾经执行过 postProcessBeanDefinitionRegistry 办法，不能反复解决
   int registryId = System.identityHashCode(registry);
   if (this.registriesPostProcessed.contains(registryId)) {
      throw new IllegalStateException("postProcessBeanDefinitionRegistry already called on this post-processor against" + registry);
   }
    // 生成 ID，如果蕴含则阐明该 BeanFactoryProcess 曾经执行过 postProcessBeanFactory 办法，不能反复解决
   if (this.factoriesPostProcessed.contains(registryId)) {
      throw new IllegalStateException("postProcessBeanFactory already called on this post-processor against" + registry);
   }
    // 记录曾经执行过 postProcessBeanDefinitionRegistry 办法
   this.registriesPostProcessed.add(registryId);

    // 验证和注册 BeanDefinitions
   processConfigBeanDefinitions(registry);
}

processConfigBeanDefinitions 逻辑次要是对配置类进行剖析，如果扫描到该配置类应用了Configuration、Component、ComponentScan、Import、ImportResource、Bean 注解，则认为是配置类。

在解析时，判断是否解析过，曾经被解析过不会再次解析，如果曾经解析过，会对其示意，依据 Configuration#proxyBeanMethods的值进行标记：true 将其标识为full，false 标识为lite。
有须要进行解析的配置类，则会依据 order 进行排列解析程序。
应用 ConfigurationClassParser 对其进行解析，将解析到的配置类返回，应用 ConfigurationClassBeanDefinitionReader 进行注册BeanDefinition。
始终依照步骤 3 进行，直到解析完所有的配置类。

/**
 * 1. 扫描入口类，在
 */
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
   String[] candidateNames = registry.getBeanDefinitionNames();

    // 查看 bean class 是否应用 Configuration、Component、ComponentScan、Import、ImportResource、Bean 注解。// 如果应用了，则将 beanDef 进行标识（ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE）。for (String beanName : candidateNames) {BeanDefinition beanDef = registry.getBeanDefinition(beanName);
       // beanDef 是否蕴含该属性，蕴含则阐明解决过
      if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {if (logger.isDebugEnabled()) {logger.debug("Bean definition has already been processed as a configuration class:" + beanDef);
         }
      }
       
      else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
         // 增加须要解析的配置类
         configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
      }
   }

   // 没有配置类，则间接返回
   // Return immediately if no @Configuration classes were found
   if (configCandidates.isEmpty()) {return;}

   // 依据 order 进行排序，从小到大，order 越小越前
   // 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
   // 设置 bean 名称生成器
   SingletonBeanRegistry 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();
   }
    
   // 解析配置类 (@configuration)
   // Parse each @Configuration class
   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 {
      // 解析
      parser.parse(candidates);
      // 验证：必须能够重写，不能是 final
      parser.validate();
      // 长期存储这次解析到的配置类
      Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
      // 移除曾经解析的配置类
      configClasses.removeAll(alreadyParsed);

      // Read the model and create bean definitions based on its content
      // 创立解析器
      if (this.reader == null) {
         this.reader = new ConfigurationClassBeanDefinitionReader(
               registry, this.sourceExtractor, this.resourceLoader, this.environment,
               this.importBeanNameGenerator, parser.getImportRegistry());
      }
      // 向 BeanFactory 中注册 beanDefinition
      this.reader.loadBeanDefinitions(configClasses);
      // 增加曾经解析的类
      alreadyParsed.addAll(configClasses);
      // 解析完后清空
      candidates.clear();
      // 将本次解析进去的配置类存入 candidates 中，以供下一次循环进行解析。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
   // 增加 ImportRegistry
   if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
   }
   // 革除缓存
   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();}
}

在整个解析过程中，ConfigurationClassParser 和 ConfigurationClassBeanDefinitionReader起着关键作用。

ConfigurationClassParser 解析配置类，会将扫描到的 ConfigurationClass 返回，交由 ConfigurationClassBeanDefinitionReader 进行注册。

在 ConfigurationClassParser 解析过程中，如果碰到 @Component、@bean、@Import等注解定义的类，将会委托给对应的处理器进行解决，这些类的解决形式与解决 @Configuration 注解定义的类不一样，在处理过程中就会将 BeanDefinition注册进BeanFactory。

ConfigurationClassParser#parse()办法剖析

parse 办法外部调用的是 ConfigurationClassParser#processConfigurationClass来进行解析

/**
 * 传入须要解析的配置类
 */
public void parse(Set<BeanDefinitionHolder> configCandidates) {for (BeanDefinitionHolder holder : configCandidates) {BeanDefinition bd = holder.getBeanDefinition();
      try {// 判断类型，各个分支最初都是调用 processConfigurationClass() 
         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);
      }
   }
   // 导入应用 ImportSelector 注解 的配置类
   this.deferredImportSelectorHandler.process();}

processConfigurationClass() 剖析


protected void processConfigurationClass(ConfigurationClass configClass, Predicate<String> filter) throws IOException {
   // 是否跳过：解析 Conditional 条件
   if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {return;}

   ConfigurationClass existingClass = this.configurationClasses.get(configClass);
   if (existingClass != null) {
      // class 解析记录曾经存在，将其合并
      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);
      }
   }
   // 从以后类开始，递归向上通过 doProcessConfigurationClass 办法解决父类，直到是由 java 提供父类或曾经解决过为止。// Recursively process the configuration class and its superclass hierarchy.
   SourceClass sourceClass = asSourceClass(configClass, filter);
   do {sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
   }
   while (sourceClass != null);
   // 记录该类曾经解决过。this.configurationClasses.put(configClass, configClass);
}

doProcessConfigurationClass 解决流程：

首先解决配置类的外部类
解决配置类上的@PropertySource 注解
解决配置类上的@ComponentScan 注解
解决配置类上的@Import 注解
解决配置类上的 @ImportResource 注解
解决在配置类中应用到的 @Bean的注解办法
解决配置类的接口默认办法
返回满足要求的父类，如果父类不须要解决或曾经解决过，返回 null，示意这个配置类曾经解决实现

protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
      throws IOException {

   // @Configuration 组合了 @Component，所以应用了 @Configuration 会进入该办法，对内部类进行递归扫描
   if (configClass.getMetadata().isAnnotated(Component.class.getName())) {// Recursively process any member (nested) classes first
      processMemberClasses(configClass, sourceClass, filter);
   }

   // 解决 @PropertySource 注解，将 @PropertySource 指定的类创立并退出到 environment 中。// Process any @PropertySource annotations
   for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(sourceClass.getMetadata(), PropertySources.class,
         org.springframework.context.annotation.PropertySource.class)) {if (this.environment instanceof ConfigurableEnvironment) {processPropertySource(propertySource);
      }
      else {logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
               "]. Reason: Environment must implement ConfigurableEnvironment");
      }
   }

   // 解决配置类上的 @ComponentScan 注解，委托给 componentScanParser 解决
   // 应用 ComponentScanAnnotationParser 扫描在配置类上应用到的 @ComponentScan 指定的包
   // 将发现的类的 BeanDefinition 注册到 BeanFactory 中。// 之后在判断这些类是否是配置类，如果是，则对其进行递归扫描。// Process any @ComponentScan annotations
   Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
   if (!componentScans.isEmpty() &&
         !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {for (AnnotationAttributes componentScan : componentScans) {
         // The config class is annotated with @ComponentScan -> perform the scan immediately
         Set<BeanDefinitionHolder> scannedBeanDefinitions =
               this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
         // Check the set of scanned definitions for any further config classes and parse recursively if needed
         for (BeanDefinitionHolder holder : scannedBeanDefinitions) {BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
            if (bdCand == null) {bdCand = holder.getBeanDefinition();
            }
            // 判断这些类是否是配置类，如果是，则对其进行递归扫描：执行 processConfigurationClass
            if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {parse(bdCand.getBeanClassName(), holder.getBeanName());
            }
         }
      }
   }

   // 解决 @Import 注解
   // 如果 @Import 指定的类实现了 ImportSelector 接口，应用 deferredImportSelectorHandler 进行解决
   // 如果实现了 ImportBeanDefinitionRegistrar 接口，则将其记录到 importBeanDefinitionRegistrars 汇合中，在执行完该办法后进行解决。// 如果不是 ImportSelector 或 ImportBeanDefinitionRegistrar 的实现类，则对指定的类执行 processConfigurationClass 办法，进行解析。// Process any @Import annotations
   processImports(configClass, sourceClass, getImports(sourceClass), filter, true);

   // 解决 @ImportResource，将其记录到 importedResources 汇合中，供前面解决
   // Process any @ImportResource annotations
   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);
      }
   }
   // 解决配置类中应用 @Bean 的办法，找到所有用 @bean 注解的办法，保留进 beanMethods 中，供前面解决
   // Process individual @Bean methods
   Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
   for (MethodMetadata methodMetadata : beanMethods) {configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
   }

   // 解决接口默认办法
   // Process default methods on interfaces
   processInterfaces(configClass, sourceClass);

   // 解析超类，如果超类不是 java 结尾并且未解决过，返回 null
   // Process superclass, if any
   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();}
   }

   // No superclass -> processing is complete
   return null;
}

关于java:spring-解析-Configuration-流程

Just My Socks（注册教程 内含优惠码）

Just My Socks（注册教程内含优惠码）