自动注入发生的时机：
1、spring refresh invokeBeanFactoryPostProcessors阶段加载 
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//这里会刷新DefaultListableBeanFactory ，DefaultListableBeanFactory 是 AbstractAutowireCapableBeanFactory 的子类，AbstractAutowireCapableBeanFactory 就是spring IOC容器2、registerBeanPostProcessors阶段加载
AutowiredAnnotationBeanPostProcessor处理器,核心方法postProcessPropertyValues，提供@Autowired类和方法级别的注入。

	@Overridepublic PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeanCreationException {InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);try {metadata.inject(bean, beanName, pvs);}catch (BeanCreationException ex) {throw ex;}catch (Throwable ex) {throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex);}return pvs;}private InjectionMetadata findAutowiringMetadata(String beanName, Class<?> clazz, PropertyValues pvs) {// Fall back to class name as cache key, for backwards compatibility with custom callers.String cacheKey = (StringUtils.hasLength(beanName) ? beanName : clazz.getName());// Quick check on the concurrent map first, with minimal locking.InjectionMetadata metadata = this.injectionMetadataCache.get(cacheKey);if (InjectionMetadata.needsRefresh(metadata, clazz)) {synchronized (this.injectionMetadataCache) {metadata = this.injectionMetadataCache.get(cacheKey);if (InjectionMetadata.needsRefresh(metadata, clazz)) {if (metadata != null) {metadata.clear(pvs);}try {metadata = buildAutowiringMetadata(clazz);this.injectionMetadataCache.put(cacheKey, metadata);}catch (NoClassDefFoundError err) {throw new IllegalStateException("Failed to introspect bean class [" + clazz.getName() +"] for autowiring metadata: could not find class that it depends on", err);}}}}return metadata;}public void inject(Object target, String beanName, PropertyValues pvs) throws Throwable {Collection<InjectedElement> elementsToIterate =(this.checkedElements != null ? this.checkedElements : this.injectedElements);if (!elementsToIterate.isEmpty()) {boolean debug = logger.isDebugEnabled();for (InjectedElement element : elementsToIterate) {if (debug) {logger.debug("Processing injected element of bean '" + beanName + "': " + element);}element.inject(target, beanName, pvs);}}}private InjectionMetadata buildAutowiringMetadata(final Class<?> clazz) {LinkedList<InjectionMetadata.InjectedElement> elements = new LinkedList<InjectionMetadata.InjectedElement>();Class<?> targetClass = clazz;do {final LinkedList<InjectionMetadata.InjectedElement> currElements =new LinkedList<InjectionMetadata.InjectedElement>();ReflectionUtils.doWithLocalFields(targetClass, new ReflectionUtils.FieldCallback() {@Overridepublic void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {AnnotationAttributes ann = findAutowiredAnnotation(field);if (ann != null) {if (Modifier.isStatic(field.getModifiers())) {if (logger.isWarnEnabled()) {logger.warn("Autowired annotation is not supported on static fields: " + field);}return;}boolean required = determineRequiredStatus(ann);currElements.add(new AutowiredFieldElement(field, required));}}});ReflectionUtils.doWithLocalMethods(targetClass, new ReflectionUtils.MethodCallback() {@Overridepublic void doWith(Method method) throws IllegalArgumentException, IllegalAccessException {Method bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);if (!BridgeMethodResolver.isVisibilityBridgeMethodPair(method, bridgedMethod)) {return;}AnnotationAttributes ann = findAutowiredAnnotation(bridgedMethod);if (ann != null && method.equals(ClassUtils.getMostSpecificMethod(method, clazz))) {if (Modifier.isStatic(method.getModifiers())) {if (logger.isWarnEnabled()) {logger.warn("Autowired annotation is not supported on static methods: " + method);}return;}if (method.getParameterTypes().length == 0) {if (logger.isWarnEnabled()) {logger.warn("Autowired annotation should only be used on methods with parameters: " +method);}}boolean required = determineRequiredStatus(ann);PropertyDescriptor pd = BeanUtils.findPropertyForMethod(bridgedMethod, clazz);currElements.add(new AutowiredMethodElement(method, required, pd));}}});elements.addAll(0, currElements);targetClass = targetClass.getSuperclass();}while (targetClass != null && targetClass != Object.class);return new InjectionMetadata(clazz, elements);}

 3、spring refresh finishBeanFactoryInitialization 中 填充Bean属性的时候触发

 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#populateBean实现

	/*** Populate the bean instance in the given BeanWrapper with the property values* from the bean definition.* @param beanName the name of the bean* @param mbd the bean definition for the bean* @param bw BeanWrapper with bean instance*/protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {PropertyValues pvs = mbd.getPropertyValues();if (bw == null) {if (!pvs.isEmpty()) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");}else {// Skip property population phase for null instance.return;}}// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the// state of the bean before properties are set. This can be used, for example,// to support styles of field injection.boolean continueWithPropertyPopulation = true;if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {for (BeanPostProcessor bp : getBeanPostProcessors()) {if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {continueWithPropertyPopulation = false;break;}}}}if (!continueWithPropertyPopulation) {return;}if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {MutablePropertyValues newPvs = new MutablePropertyValues(pvs);// Add property values based on autowire by name if applicable.if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {autowireByName(beanName, mbd, bw, newPvs);}// Add property values based on autowire by type if applicable.if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {autowireByType(beanName, mbd, bw, newPvs);}pvs = newPvs;}boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);if (hasInstAwareBpps || needsDepCheck) {PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);if (hasInstAwareBpps) {for (BeanPostProcessor bp : getBeanPostProcessors()) {if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;//核心：这里负责注入执行Autowired的类和方法pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);if (pvs == null) {return;}}}}if (needsDepCheck) {checkDependencies(beanName, mbd, filteredPds, pvs);}}applyPropertyValues(beanName, mbd, bw, pvs);}