Spring BeanDefinition
spring容器托管的对象即是一个个BeanDefinition,其类的层次结构如图所示：
@Import引入的class在解析的时候对应AnnotatedGenericBeanDefinition
BeanMethod(@Bean)解析的时候对应ConfigurationClassBeanDefinition
ApplicationContext作为spring central interfacae， 提供以下功能：
- Bean factory methods for accessing application components. 继承ListableBeanFactory接口
- 加载资源文件，继承ResourceLoader接口
- 向注册的listener发布事件，继承ApplicationEventPublisher接口
- 解析message source，支持国际化，继承MessageSource接口
Spring ApplicationContext 简略层次结构如图所示:
spring boot 启动时代码片段
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = prepareEnvironment(listener,applicationArguments);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();//创建上下文
analyzers = new FailureAnalyzers(context);
prepareContext(context, environment, listeners, applicationArguments,printedBanner);
refreshContext(context);//刷新上下文
afterRefresh(context, applicationArguments);
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}
return context;
}catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers,ex);
throw new IllegalStateException(ex);
}
}
创建上下文：
注册BeanFactoryPostProcessor、BeanPostProcessor
创建上下文如果是在web环境上下文类型为：AnnotationConfigEmbeddedWebApplicationContext；否则为默认实现AnnotationConfigApplicationContext
protected ConfigurableApplicationContext createApplicationContext() {
Class contextClass = this.applicationContextClass;
if (contextClass == null) {
try {
contextClass = Class.forName(this.webEnvironment ? DEFAULT_WEB_CONTEXT_CLASS : DEFAULT_CONTEXT_CLASS);
} catch (ClassNotFoundException ex) {
throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass",ex);
}
}
return (ConfigurableApplicationContext) BeanUtils.instantiate(contextClass);
}
实例化contextClass时，向BeanFactory注册BeanFactoryPostProcessor,以及BeanPostProcessor;
ConfigurationClassPostProcessor(处理@Configuration注解)
AutowiredAnnotationBeanPostProcessor(处理@Autowire,@Inject,@Value注解)
RequiredAnnotationBeanPostProcessor(处理@Requried注解)
CommonAnnotationBeanPostProcessor(处理 @Resource注解)
AnnotationConfigUtils 代码片段
public static Set registerAnnotationConfigProcessors(BeanDefinitionRegistry registry, Object source) {
…
Set beanDefs = new LinkedHashSet(4);
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));
}
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));
}
// 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));
}
…
return beanDefs;
}
刷新上下文：
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in contex subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this
context.initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
} catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - "
+ "cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
prepareRefresh
设置开始时间，active,closed标志位，以及初始化Property Resource
prepareBeanFactory
配置BeanFactory的标准上下文特征，注册BeanPostProcessor等
StandardBeanExpressionResolver（解析SPEL表达式），ApplicationContextAwareProcessor(BeanPostProcessor)
postProcessBeanFactory
扩展方法，可用于注册beanDefinition
比如：AnnotationConfigEmbeddedWebApplicationContext
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.postProcessBeanFactory(beanFactory);
if (this.basePackages != null && this.basePackages.length > 0) {
this.scanner.scan(this.basePackages);
}
if (this.annotatedClasses != null && this.annotatedClasses.length > 0) {
this.reader.register(this.annotatedClasses);
}
}
invokeBeanFactoryPostProcessors
BeanFactoryPostProcessor部分类层次结构
调用过程：
-
优先调用BeanDefinitionRegistryPostProcessor，处理顺序如图所示:
First: 调用实现PriorityOrdered接口，ex:ConfigurationClassPostProcessor
Second: 调用实现Ordered接口
Third: 调用普通类型
-
再者调用实现BeanFactoryPostProcessor接口的类
First: 调用实现PriorityOrdered接口
Second: 调用实现Ordered接口
Third: 调用普通类型
registerBeanPostProcessors
注册BeanPostProcessors至BeanFactory,在创建Bean时调用
initMessageSource
初始化Message Resource
initApplicationEventMulticaster
初始化ApplicationEventMulticaster
onRefresh
模板方法，子类可重载
registerListeners
注册实现了ApplicationListener接口的listener
finishBeanFactoryInitialization
初始化BeanFactory里的Bean，懒加载Bean在此处不会初始化
finishRefresh
调用LifecycleProcessor的onRefresh，发布ContextRefreshedEvent事件