AnnotationConfigApplicationContext(1)之初始化Scanner和Reader
AnnotationConfigApplicationContext(1)初始化Scanner和Reader
我们以AnnotationConfigApplicationContext为起点来探究Spring的启动过程
首先映入眼帘的就是AnnotationConfigApplicationContext的构造方法，而我们今天只来探讨this();
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
//this()方法这里就创建了一个Bean工厂和Reader和Scanner
this();
register(componentClasses);
refresh();
}
public AnnotationConfigApplicationContext() {
StartupStep createAnnotatedBeanDefReader = this.getApplicationStartup().start("spring.context.annotated-bean-reader.create");
// 生成并注册5个BeanDefinition
// 1.ConfigurationClassPostProcessor
// 2.AutowiredAnnotationBeanPostProcessor
// 3.CommonAnnotationBeanPostProcessor
// 4.EventListenerMethodProcessor
// 5.DefaultEventListenerFactory
this.reader = new AnnotatedBeanDefinitionReader(this);
createAnnotatedBeanDefReader.end();
// 注册默认的includeFilter
this.scanner = new ClassPathBeanDefinitionScanner(this);
}
AnnotationConfigApplicationContext首先会生成Reader和Scanner，但在这之前，BeanFactory其实已经实例化完成了
因为AnnotationConfigApplicationContext是GenericApplicationContext的子类，父类的构造器要优先于子类构造器执行，所以在执行AnnotationConfigApplicationContext类的无参构造时，会先执行GenericApplicationContext的无参构造：
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}
一、AnnotatedBeanDefinitionReader
Spring在实例化AnnotatedBeanDefinitionReader做了很多，最主要的就是将内部的后置处理器注册到Spring中
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;
//ConditionEvaluator对象封装了spring容器的信息
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
/**
* 将所有相关的后置处理器注册到这个registry中
*/
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
将spring相关信息记录到conditionEvaluator对象后，spring开始注册相关后置处理器
public static SetregisterAnnotationConfigProcessors(BeanDefinitionRegistry registry, @Nullable Object source) { //将刚刚开始第一次new得bean工厂获得， DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); if (beanFactory != null) { //加载组件，其中包括AnnotationAwareOrderComparator和ContextAnnotationAutowireCandidateResolver //AnnotationAwareOrderComparator可以对实现PriorityOrdered、Ordered以及被@Order注解修饰的类进行统一的排序 if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) { beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE); } //AutowireCandidateResolver 用来判断一个给定的 bean 是否可以注入，最主要的方法是 isAutowireCandidate if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) { beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); } } //BeanDefinitionHolder中有beanDefinition，beanName,alias Set beanDefs = new LinkedHashSet<>(8); if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class); def.setSource(source); //null /** * registerPostProcessor方法： * 将beanName和BeanDefinition按Key—value键值对得方式放在BeanDefinitionMap中 * 将BeanName放在BeanDefinitionNames列表中， * 将BeanName和BeanDefinition封装在BeanDefinitionHolder中， * 将封装好得BeanDefinitionHolder放在BeanDefs列表中。 * 这里其实就是注册内部的后置处理器 */ beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)); } //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)); } // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor. 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)); } // 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)); } //EventListenerMethodProcessor 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)); }inter //DefaultEventListenerFactory 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; }
二、ClassPathBeanDefinitionScanner
public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
Environment environment, @Nullable ResourceLoader resourceLoader) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
this.registry = registry;
if (useDefaultFilters) {
//添加includeFilters
//注册一个@Component注解对应的Filter
registerDefaultFilters();
}
setEnvironment(environment);
setResourceLoader(resourceLoader);
}
在开篇的时候我们提到了Scanner的用法，其中就提及到了includeFilters
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
ClassPathBeanDefinitionScanner classPathBeanDefinitionScanner = new ClassPathBeanDefinitionScanner(factory);
//得到该包下类的个数
// int scan = classPathBeanDefinitionScanner.scan("com.beans");
// System.out.println(scan);//6
//扫描没有加@Componment注解的类，并注册到容器中，未通过注解或其他方式定义Bean的类也不会添加到容器中
//classPathBeanDefinitionScanner.addExcludeFilter(new AnnotationTypeFilter(Component.class));
//扫描加了@Componment注解的类，并注册到容器中
classPathBeanDefinitionScanner.addIncludeFilter(new AnnotationTypeFilter(Component.class));
//获取bean
Object bean = factory.getBean(BeanTest.class);
System.out.println(bean);//com.beans.BeanTest@5ccddd20
Spring会默认向includeFilters添加了@Componment注解
protected void registerDefaultFilters() {
this.includeFilters.add(new AnnotationTypeFilter(Component.class));
ClassLoader cl = ClassPathScanningCandidateComponentProvider.class.getClassLoader();
try {
this.includeFilters.add(new AnnotationTypeFilter(((Class<? extends Annotation>) ClassUtils.forName("javax.annotation.ManagedBean", cl)), false));
logger.trace("JSR-250 'javax.annotation.ManagedBean' found and supported for component scanning");
}catch (ClassNotFoundException ex) {
// JSR-250 1.1 API (as included in Java EE 6) not available - simply skip.
}
try {
this.includeFilters.add(new AnnotationTypeFilter(((Class<? extends Annotation>) ClassUtils.forName("javax.inject.Named", cl)), false));
logger.trace("JSR-330 'javax.inject.Named' annotation found and supported for component scanning");
}catch (ClassNotFoundException ex) {
// JSR-330 API not available - simply skip.
}
}
到这里Spring就完成了AnnotatedBeanDefinitionReader和ClassPathBeanDefinitionScanner注解的实例化