Spring 5.x 源码之旅-30getBean详解十五initializeBean一

    	protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
    		if (System.getSecurityManager() != null) {
    			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
    				invokeAwareMethods(beanName, bean);
    				return null;
    			}, getAccessControlContext());
    		}
    		else {//Aware接口处理器
    			invokeAwareMethods(beanName, bean);
    		}
    
    		Object wrappedBean = bean;
    		if (mbd == null || !mbd.isSynthetic()) {//初始化前
    			wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
    		}
    
    		try {//初始化
    			invokeInitMethods(beanName, wrappedBean, mbd);
    		}
    		catch (Throwable ex) {
    			throw new BeanCreationException(
    					(mbd != null ? mbd.getResourceDescription() : null),
    					beanName, "Invocation of init method failed", ex);
    		}
    		if (mbd == null || !mbd.isSynthetic()) {//初始化后
    			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    		}
    
    		return wrappedBean;
    	}

invokeAwareMethods触发提示方法

处理BeanNameAware，BeanClassLoaderAware，BeanFactoryAware接口方法，这里BeanFactoryAware的接口要注意，如果前面配置类有CGLIB动态代理的话，这里这个方法就重复了，也就是setBeanFactory被重复调用了两次，前面一次是在EnhancedConfiguration接口的方法。

    private void invokeAwareMethods(final String beanName, final Object bean) {
    		if (bean instanceof Aware) {
    			if (bean instanceof BeanNameAware) {//设置bean名字
    				((BeanNameAware) bean).setBeanName(beanName);
    			}
    			if (bean instanceof BeanClassLoaderAware) {
    				ClassLoader bcl = getBeanClassLoader();
    				if (bcl != null) {//设置类加载器
    					((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
    				}
    			}
    			if (bean instanceof BeanFactoryAware) {//设置BeanFactory
    				((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
    			}
    		}
    	}

applyBeanPostProcessorsBeforeInitialization初始化之前处理

所有BeanPostProcessor 处理，如果有返回null了就直接返回，否则就把处理后的对象替换原来的，返回最新对象。

    	@Override
    	public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
    			throws BeansException {
    
    		Object result = existingBean;
    		for (BeanPostProcessor processor : getBeanPostProcessors()) {
    			Object current = processor.postProcessBeforeInitialization(result, beanName);
    			if (current == null) {
    				return result;
    			}
    			result = current;
    		}
    		return result;
    	}

ApplicationContextAwareProcessor的postProcessBeforeInitialization

如果发现bean有实现那一堆接口任意一个的话，就会执行invokeAwareInterfaces方法。

    @Override
    	@Nullable
    	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    		if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
    				bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
    				bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)){
    			return bean;
    		}
    
    		AccessControlContext acc = null;
    
    		if (System.getSecurityManager() != null) {
    			acc = this.applicationContext.getBeanFactory().getAccessControlContext();
    		}
    
    		if (acc != null) {
    			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
    				invokeAwareInterfaces(bean);
    				return null;
    			}, acc);
    		}
    		else {
    			invokeAwareInterfaces(bean);
    		}
    
    		return bean;
    	}

invokeAwareInterfaces

其实就是设置一些值，方便外部获取，做一些扩展。

    private void invokeAwareInterfaces(Object bean) {
    		if (bean instanceof EnvironmentAware) {
    			((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
    		}
    		if (bean instanceof EmbeddedValueResolverAware) {
    			((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
    		}
    		if (bean instanceof ResourceLoaderAware) {
    			((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
    		}
    		if (bean instanceof ApplicationEventPublisherAware) {
    			((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
    		}
    		if (bean instanceof MessageSourceAware) {
    			((MessageSourceAware) bean).setMessageSource(this.applicationContext);
    		}
    		if (bean instanceof ApplicationContextAware) {
    			((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
    		}
    	}

ConfigurationClassPostProcessor内部类ImportAwareBeanPostProcessor的postProcessBeforeInitialization

如果是ImportAware类型的，就会设置bean的注解信息。

    @Override
    		public Object postProcessBeforeInitialization(Object bean, String beanName) {
    			if (bean instanceof ImportAware) {
    				ImportRegistry ir = this.beanFactory.getBean(IMPORT_REGISTRY_BEAN_NAME, ImportRegistry.class);
    				AnnotationMetadata importingClass = ir.getImportingClassFor(ClassUtils.getUserClass(bean).getName());
    				if (importingClass != null) {
    					((ImportAware) bean).setImportMetadata(importingClass);
    				}
    			}
    			return bean;
    		}

InitDestroyAnnotationBeanPostProcessor的postProcessBeforeInitialization

这里就是我们前面注册的生命周期元数据，这个时候要进行调用了。

    @Override
    	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    		LifecycleMetadata metadata = findLifecycleMetadata(bean.getClass());
    		try {
    			metadata.invokeInitMethods(bean, beanName);
    		}
    		catch (InvocationTargetException ex) {
    			throw new BeanCreationException(beanName, "Invocation of init method failed", ex.getTargetException());
    		}
    		catch (Throwable ex) {
    			throw new BeanCreationException(beanName, "Failed to invoke init method", ex);
    		}
    		return bean;
    	}

LifecycleMetadata 的invokeInitMethods

调用前面注册的初始化方法集合checkedInitMethods的每一个方法。

    	public void invokeInitMethods(Object target, String beanName) throws Throwable {
    			Collection<LifecycleElement> checkedInitMethods = this.checkedInitMethods;
    			Collection<LifecycleElement> initMethodsToIterate =
    					(checkedInitMethods != null ? checkedInitMethods : this.initMethods);
    			if (!initMethodsToIterate.isEmpty()) {
    				for (LifecycleElement element : initMethodsToIterate) {
    					if (logger.isTraceEnabled()) {
    						logger.trace("Invoking init method on bean '" + beanName + "': " + element.getMethod());
    					}
    					element.invoke(target);
    				}
    			}
    		}

LifecycleElement的invoke

就是方法的反射调用，参数是null。

    		public void invoke(Object target) throws Throwable {
    			ReflectionUtils.makeAccessible(this.method);
    			this.method.invoke(target, (Object[]) null);
    		}