Spring原始碼-04-註解Bean讀取器

AnnotatedBeanDefinitionReader

一 構造方法

public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
		Assert.notNull(environment, "Environment must not be null");
		this.registry = registry;
		this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
		/**
		 * 向IoC容器註冊BeanDefinition
		 *     - 所謂註冊就是放到IoC容器中 將來在例項化Bean過程中發揮作用
		 *         - IoC容器中DefaultListableBeanFactory
		 *         - 快取到beanFactory的beanDefinitionMap中
		 *     - BeanDefinition的角色是後置處理器
		 *     - 嘗試將以下幾個註冊到IoC容器中
		 *         - ConfigurationClassPostProcessor
		 *         - AutowiredAnnotationBeanPostProcessor
		 *         - CommonAnnotationBeanPostProcessor
		 *         - InitDestroyAnnotationBeanPostProcessor
		 *         - PersistenceAnnotationBeanPostProcessor
		 *         - EventListenerMethodProcessor
		 *         - DefaultEventListenerFactory
		 */
		AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
	}
 

二 registry

也就是Bean讀取器持有IoC容器例項

三 註冊後置處理器

// AnnotationConfigUtils.java
public static void registerAnnotationConfigProcessors(BeanDefinitionRegistry registry) {
		registerAnnotationConfigProcessors(registry, null);
	}

// AnnotationConfigUtils.java
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
			BeanDefinitionRegistry registry, @Nullable Object source) {

		DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
		if (beanFactory != null) {
			if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
				beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
			}
			if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
				beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
			}
		}

		Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);

		if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		// Check for Jakarta Annotations support, and if present add the CommonAnnotationBeanPostProcessor.
		if (jakartaAnnotationsPresent && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		// Check for JSR-250 support, and if present add an InitDestroyAnnotationBeanPostProcessor
		// for the javax variant of PostConstruct/PreDestroy.
		if (jsr250Present && !registry.containsBeanDefinition(JSR250_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			try {
				RootBeanDefinition def = new RootBeanDefinition(InitDestroyAnnotationBeanPostProcessor.class);
				def.getPropertyValues().add("initAnnotationType", classLoader.loadClass("javax.annotation.PostConstruct"));
				def.getPropertyValues().add("destroyAnnotationType", classLoader.loadClass("javax.annotation.PreDestroy"));
				def.setSource(source);
				beanDefs.add(registerPostProcessor(registry, def, JSR250_ANNOTATION_PROCESSOR_BEAN_NAME));
			}
			catch (ClassNotFoundException ex) {
				// Failed to load javax variants of the annotation types -> ignore.
			}
		}

		// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
		if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition();
			try {
				def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
						AnnotationConfigUtils.class.getClassLoader()));
			}
			catch (ClassNotFoundException ex) {
				throw new IllegalStateException(
						"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
			}
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
		}

		if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
		}

		return beanDefs;
	}
 

// AnnotationConfigUtils.java
private static BeanDefinitionHolder registerPostProcessor(
			BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) {

		definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		registry.registerBeanDefinition(beanName, definition); // BeanDefinition註冊到IoC容器
		return new BeanDefinitionHolder(definition, beanName);
	}
 

BeanDefinition註冊IoC容器傳送門

四 示意圖

讀取器的職責就是前置化向IoC容器中註冊幾個特定的後置處理器，將來在Bean的生命週期中發揮作用

五 註冊配置類

// AnnotationConfigApplicationContext.java
this.register(componentClasses); // Bean讀取器讀取註解Bean將類資訊封裝BeanDefinition注入容器 配置類

// AnnotationConfigApplicationContext.java
@Override
	public void register(Class<?>... componentClasses) {
		Assert.notEmpty(componentClasses, "At least one component class must be specified");
		StartupStep registerComponentClass = this.getApplicationStartup().start("spring.context.component-classes.register")
				.tag("classes", () -> Arrays.toString(componentClasses));
		this.reader.register(componentClasses);
		registerComponentClass.end();
	}

// AnnotatedBeanDefinitionReader.java
public void register(Class<?>... componentClasses) {
		for (Class<?> componentClass : componentClasses) {
			this.registerBean(componentClass);
		}
	}

// AnnotatedBeanDefinitionReader.java
public void registerBean(Class<?> beanClass) {
		this.doRegisterBean(beanClass, null, null, null, null);
	}

// AnnotatedBeanDefinitionReader.java
private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name,
			@Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier,
			@Nullable BeanDefinitionCustomizer[] customizers) {

		AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass); // 封裝BeanDefinition
		if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
			return;
		}

		abd.setInstanceSupplier(supplier);
		ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
		abd.setScope(scopeMetadata.getScopeName());
		String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));

		AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
		if (qualifiers != null) {
			for (Class<? extends Annotation> qualifier : qualifiers) {
				if (Primary.class == qualifier) {
					abd.setPrimary(true);
				}
				else if (Lazy.class == qualifier) {
					abd.setLazyInit(true);
				}
				else {
					abd.addQualifier(new AutowireCandidateQualifier(qualifier));
				}
			}
		}
		if (customizers != null) {
			for (BeanDefinitionCustomizer customizer : customizers) {
				customizer.customize(abd);
			}
		}

		BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
		definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry); // BeanDefinition註冊到IoC容器
	}

Bean定義傳送

// BeanDefinitionReaderUtils.java
public static void registerBeanDefinition(
			BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
			throws BeanDefinitionStoreException {

		// Register bean definition under primary name.
		String beanName = definitionHolder.getBeanName();
		registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // BeanDefinition註冊IoC容器

		// Register aliases for bean name, if any.
		String[] aliases = definitionHolder.getAliases();
		if (aliases != null) {
			for (String alias : aliases) {
				registry.registerAlias(beanName, alias);
			}
		}
	}

BeanDefinition註冊IoC容器傳送門