This article mainly describes how Spring parses "annotation-config", which actually loads the annotation corresponding parser.
parse content
1. The analyzed elements are:
<context:annotation-config/>
2. Load the parser corresponding to the annotation.
Load parser
AnnotationConfigBeanDefinitionParser.parse(Element element, ParserContext parserContext)
The element here is "context:annotation-config".
public BeanDefinition parse(Element element, ParserContext parserContext) {
Object source = parserContext.extractSource(element);
// 获取所有处理注解类的BeanPostProcessors(BeanPostProcessor本身也是bean) 注1
Set<BeanDefinitionHolder> processorDefinitions =
AnnotationConfigUtils.registerAnnotationConfigProcessors(parserContext.getRegistry(), source);
// 生成关于元素(context:annotation-config)的组合组件(Component即bean),放到到解析容器待处理队列containingComponents中
CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
parserContext.pushContainingComponent(compDefinition);
// 把注解BeanPostProcessor的BeanDefinition转换成ComponentDefinition,注册到解析容器的containingComponents的嵌套组件中
for (BeanDefinitionHolder processorDefinition : processorDefinitions) {
parserContext.registerComponent(new BeanComponentDefinition(processorDefinition));
}
// 触发组件注册事件
parserContext.popAndRegisterContainingComponent();
return null;
}
Note 1: BeanPostProcessors of annotation classes are provided by the SF framework.
AnnotationConfigUtils.registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, @Nullable Object source)
1. Set the attribute instances of the bean factory for annotation processing (including: AnnotationAwareOrderComparator, ContextAnnotationAutowireCandidateResolver, ContextAnnotationAutowireCandidateResolver)
2. Use Spring to parse the processor beans for annotations (including: ConfigurationClassPostProcessor, AutowiredAnnotationBeanPostProcessor, CommonAnnotationBeanPostProcessor, InitDestroyAnnotationBeanPostProcessor , PersistenceAnnotationBeanPostProcessor, EventListenerMethodProcessor, DefaultEventListenerFactory) The BeanDefinition formed collection returns
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
BeanDefinitionRegistry registry, Object source) {
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
// 设置dependencyComparator属性
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
}
if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
// 设置autowireCandidateResolver属性(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)
beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
}
}
Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(4);
// 注册内部管理的用于处理@Configuration注解的后置处理器bean-ConfigurationClassPostProcessor
if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
def.setSource(source);
// registerPostProcessor: 注册BeanDefinition到注册表中
beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
}
// 注册内部管理的用于处理@Autowired、@Value、@Inject以及@Lookup注解的后置处理器bean-AutowiredAnnotationBeanPostProcessor
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));
}
// 支持Jakarta注解,注册内部管理注解通用后置处理器bean-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));
}
// 支持JSR-250注解(@PostConstruct,@PreDestroy)后置处理器的bean-InitDestroyAnnotationBeanPostProcessor
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.
}
}
// 注册内部管理的用于处理JPA注解的后置处理器bean-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));
}
// 注册内部管理的用于处理@EventListener注解的后置处理器bean
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));
}
// 注册内部管理用于生产ApplicationListener对象的EventListenerFactory对象
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;
}
private static BeanDefinitionHolder registerPostProcessor(
BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) {
// 设置role
definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
// 注册BeanDefinition
registry.registerBeanDefinition(beanName, definition);
// 封装成BeanDefinitionHolder并返回
return new BeanDefinitionHolder(definition, beanName);
}