Spring4.3.x 浅析xml配置的解析过程（7）——解析context命名空间之annotation-config标签

2019-11-10 17:34:15

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概述

SPRing context命名空间有property-placeholder、property-override、annotation-config、component-scan、load-time-weaver、spring-configured、mbean-export和mbean-server 8个标签。

上一节探讨了 property-placeholder和property-override标签的解析，这一节来探讨一下annotation-config的解析与用途。

解析annotation-config标签

annotation-config标签用于向BeanDefinitionRegistry对象（BeanDefinition注册表）中注册处理注解配置的工厂后处理器类和bean后处理器类以及其他一些特定类对应的BeanDefinition对象。这些类和注解有

处理@Configuration注解的ConfigurationClassPostProcessor工厂后处理器；

处理@Autowired、@Value、@Inject以及@Lookup注解的AutowiredAnnotationBeanPostProcessor bean后处理器；

处理@Required注解的RequiredAnnotationBeanPostProcessor bean后处理器；

处理JSR-250的@Resource、@PostConstruct、@PreDestroy、@EJB和@WebServiceRef注解的CommonAnnotationBeanPostProcessor bean后处理器；

处理JPA注解的PersistenceAnnotationBeanPostProcessor bean后处理器

处理@EventListener注解的EventListenerMethodProcessor后处理器和创建applicationListener对象的EventListenerFactory对象。

annotation-config标签的解析器类为AnnotationConfigBeanDefinitionParser，它直接实现了BeanDefinitionParser接口，下面是它实现的parse方法的源代码。

@Override public BeanDefinition parse(Element element, ParserContext parserContext) { Object source = parserContext.extractSource(element); // 注册所有相关的BeanPostProcessor. Set<BeanDefinitionHolder> processorDefinitions = AnnotationConfigUtils.registerAnnotationConfigProcessors(parserContext.getRegistry(), source); CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source); parserContext.pushContainingComponent(compDefinition); for (BeanDefinitionHolder processorDefinition : processorDefinitions) { parserContext.registerComponent(new BeanComponentDefinition(processorDefinition)); } // 最后注册 composite component. parserContext.popAndRegisterContainingComponent(); return null; }

parse方法主要调用注解配置工具类AnnotationConfigUtils的registerAnnotationConfigProcessors静态方法来注册于注解配置有关的bean后处理器，这个方法的源码如下。

private static final boolean jsr250Present = ClassUtils.isPresent("javax.annotation.Resource", AnnotationConfigUtils.class.getClassLoader()); // 定义常量PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME // = "org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" private static final boolean jpaPresent = ClassUtils.isPresent("javax.persistence.EntityManagerFactory", AnnotationConfigUtils.class.getClassLoader()) && ClassUtils.isPresent(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, AnnotationConfigUtils.class.getClassLoader()); /** * 注册用于注解配置的bean后处理器 **/ public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, Object source) { DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); if (beanFactory != null) { if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) { beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE); } // 设置自动注入候选对象的解析器，用于判断BeanDefinition是否为候选对象 if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) { beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); } } Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(4); // 设置处理@Configuration注解的工厂后处理器 // 常量CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME // ="org.springframework.context.annotation.internalConfigurationAnnotationProcessor"; 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)); } // 设置用于处理@Autowired、@Value、@Inject以及@Lookup注解 // 定义常量AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME // = "org.springframework.context.annotation.internalAutowiredAnnotationProcessor" 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)); } // 设置处理@Required注解的bean后处理器 // 定义常量REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME // = "org.springframework.context.annotation.internalRequiredAnnotationProcessor" if (!registry.containsBeanDefinition(REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(RequiredAnnotationBeanPostProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } // 设置处理JSR-250提供的注解的bean后处理器。 // 比如，@Resource, @PostConstruct, @PreDestroy, @EJB, @WebServiceRef // 检查系统是否支持JSR-250 // 定义常量COMMON_ANNOTATION_PROCESSOR_BEAN_NAME // = "org.springframework.context.annotation.internalCommonAnnotationProcessor"; if (jsr250Present && !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)); } // 注册用于处理JPA注解的bean后处理器 // 检查系统是否支持JPA // 定义常量PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME // = "org.springframework.context.annotation.internalPersistenceAnnotationProcessor" if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(); try { // 定义常量PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME // = "org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" 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)); } // 设置用于处理@EventListener注解的bean后处理器 // 定义常量EVENT_LISTENER_PROCESSOR_BEAN_NAME // = "org.springframework.context.event.internalEventListenerProcessor" 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)); } // 设置用于生产ApplicationListener对象的EventListenerFactory对象 // 定义常量EVENT_LISTENER_FACTORY_BEAN_NAME // = "org.springframework.context.event.internalEventListenerFactory" 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用于注册BeanDefinition的registerPostProcessor静态方法的代码如下。

/** * 注册RootBeanDefinition对象 **/ private static BeanDefinitionHolder registerPostProcessor( BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) { definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE); registry.registerBeanDefinition(beanName, definition); return new BeanDefinitionHolder(definition, beanName); }