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1.BeanPostProcessor 执行原理
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) { this(); register(annotatedClasses); refresh(); }
// Instantiate all remaining (non-lazy-init) singletons. finishBeanFactoryInitialization(beanFactory);
// Instantiate all remaining (non-lazy-init) singletons. beanFactory.preInstantiateSingletons();
getBean(beanName);
// Create bean instance. if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() { @Override public Object getObject() throws BeansException { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { // Explicitly remove instance from singleton cache: It might have been put there // eagerly by the creation process, to allow for circular reference resolution. // Also remove any beans that received a temporary reference to the bean. destroySingleton(beanName); throw ex; } } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); }
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
Object exposedObject = bean; try { populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { exposedObject = initializeBean(beanName, exposedObject, mbd); } }
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
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()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
result = beanProcessor.postProcessBeforeInitialization(result, beanName);
if (result == null) {
return result;
}
}
return result;
}
populateBean() 函数进行填充,invokeInitMethods(beanName, wrappedBean, mbd);
函数进行初始化,然后前后有applyBeanPostProcessorsBeforeInitialization 和applyBeanPostProcessorsAfterInitialization 进行对所有的BeanPostProcessor 扫描执行。
2.BeanPostProcessor 在spring 中的应用
@Component
public class Dog implements ApplicationContextAware {
private ApplicationContext applicationContext;
public Dog(){
System.out.println("dog constructor...");
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
// TODO Auto-generated method stub
this.applicationContext = applicationContext;
}
}
2.通过invokeAwareInterfaces判断Bean 的类型进行类型转换,并进行赋值
private void invokeAwareInterfaces(Object bean) { if (bean instanceof Aware) { 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); } } }
@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; }
public void invokeInitMethods(Object target, String beanName) throws Throwable { Collection<LifecycleElement> initMethodsToIterate = (this.checkedInitMethods != null ? this.checkedInitMethods : this.initMethods); if (!initMethodsToIterate.isEmpty()) { boolean debug = logger.isDebugEnabled(); for (LifecycleElement element : initMethodsToIterate) { if (debug) { logger.debug("Invoking init method on bean '" + beanName + "': " + element.getMethod()); } element.invoke(target); } }}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!this.afterInitialization) {
doValidate(bean);
}
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (this.afterInitialization) {
doValidate(bean);
}
return bean;
}
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