AnnotationConfigApplicationContext(1)初始化Scanner和Reader
我們以AnnotationConfigApplicationContext為起點來探究Spring的啟動過程
首先映入眼簾的就是AnnotationConfigApplicationContext的構造方法，而我們今天只來探討this();
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
//this()方法這裡就建立了一個Bean工廠和Reader和Scanner
this();
register(componentClasses);
refresh();
}
public AnnotationConfigApplicationContext() {
StartupStep createAnnotatedBeanDefReader = this.getApplicationStartup().start("spring.context.annotated-bean-reader.create");
// 生成並註冊5個BeanDefinition
// 1.ConfigurationClassPostProcessor
// 2.AutowiredAnnotationBeanPostProcessor
// 3.CommonAnnotationBeanPostProcessor
// 4.EventListenerMethodProcessor
// 5.DefaultEventListenerFactory
this.reader = new AnnotatedBeanDefinitionReader(this);
createAnnotatedBeanDefReader.end();
// 註冊預設的includeFilter
this.scanner = new ClassPathBeanDefinitionScanner(this);
}
AnnotationConfigApplicationContext首先會生成Reader和Scanner，但在這之前，BeanFactory其實已經例項化完成了
因為AnnotationConfigApplicationContext是GenericApplicationContext的子類，父類的構造器要優先於子類構造器執行，所以在執行AnnotationConfigApplicationContext類的無參構造時，會先執行GenericApplicationContext的無參構造：
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}
一、AnnotatedBeanDefinitionReader
Spring在例項化AnnotatedBeanDefinitionReader做了很多，最主要的就是將內部的後置處理器註冊到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物件封裝了spring容器的資訊
this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
/**
* 將所有相關的後置處理器註冊到這個registry中
*/
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
將spring相關資訊記錄到conditionEvaluator物件後，spring開始註冊相關後置處理器
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(BeanDefinitionRegistry registry, @Nullable Object source) {
//將剛剛開始第一次new得bean工廠獲得，
DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
if (beanFactory != null) {
//載入元件，其中包括AnnotationAwareOrderComparator和ContextAnnotationAutowireCandidateResolver
//AnnotationAwareOrderComparator可以對實現PriorityOrdered、Ordered以及被@Order註解修飾的類進行統一的排序
if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
}
//AutowireCandidateResolver 用來判斷一個給定的 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<BeanDefinitionHolder> 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：
* 將beanName和BeanDefinition按Key—value鍵值對得方式放在BeanDefinitionMap中
* 將BeanName放在BeanDefinitionNames列表中，
* 將BeanName和BeanDefinition封裝在BeanDefinitionHolder中，
* 將封裝好得BeanDefinitionHolder放在BeanDefs列表中。
* 這裡其實就是註冊內部的後置處理器
*/
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) {
//新增includeFilters
//註冊一個@Component註解對應的Filter
registerDefaultFilters();
}
setEnvironment(environment);
setResourceLoader(resourceLoader);
}
在開篇的時候我們提到了Scanner的用法，其中就提及到了includeFilters
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
ClassPathBeanDefinitionScanner classPathBeanDefinitionScanner = new ClassPathBeanDefinitionScanner(factory);
//得到該包下類的個數
// int scan = classPathBeanDefinitionScanner.scan("com.beans");
// System.out.println(scan);//6
//掃描沒有加@Componment註解的類，並註冊到容器中，未通過註解或其他方式定義Bean的類也不會新增到容器中
//classPathBeanDefinitionScanner.addExcludeFilter(new AnnotationTypeFilter(Component.class));
//掃描加了@Componment註解的類，並註冊到容器中
classPathBeanDefinitionScanner.addIncludeFilter(new AnnotationTypeFilter(Component.class));
//獲取bean
Object bean = factory.getBean(BeanTest.class);
System.out.println(bean);//com.beans.BeanTest@5ccddd20
Spring會預設向includeFilters新增了@Componment註解
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.
}
}
到這裡Spring就完成了AnnotatedBeanDefinitionReader和ClassPathBeanDefinitionScanner註解的例項化