【spring源码系列】之【Bean的属性赋值】

每次进入源码的世界，就像完成一场奇妙的旅行！

1. 属性赋值概述

上一篇讲述了bean实例化中的创建实例过程，实例化后就需要对类中的属性进行依赖注入操作，本篇将重点分析属性赋值相关流程。其中属性赋值，体现在AbstractAutowireCapableBeanFactory类中的doCreateBean方法中的populateBean(beanName, mbd, instanceWrapper)这行代码；在赋值之前还做了收集属性的相关操作，下面就通过源码来分析。

2. 流程概览

流程中分为三步：

step1:通过BeanPostProcessor的实现类，实现了带注解的属性收集，CommonAnnotationBeanPostProcessor 支持了@PostContructor、@PreDestroy、@Resource的收集；AutowiredAnnotationBeanPostProcessor支持@Autowired、@value注解的属性收集；

step2:将收集有注解属性和方法封装到对应的容器中；

step3:遍历容器中的属性，注入到对应的bean实例中。

3. 源码分析

3.1 收集@PostConstruct @PreDestroy注解的方法

首先AbstractAutowireCapableBeanFactory类中的doCreateBean`方法：

protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
			throws BeanCreationException {

		// Instantiate the bean.
		BeanWrapper instanceWrapper = null;
		if (mbd.isSingleton()) {
			instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
		}
		if (instanceWrapper == null) {
			//创建对象实例
			instanceWrapper = createBeanInstance(beanName, mbd, args);
		}
		Object bean = instanceWrapper.getWrappedInstance();
		Class<?> beanType = instanceWrapper.getWrappedClass();
		if (beanType != NullBean.class) {
			mbd.resolvedTargetType = beanType;
		}

		// Allow post-processors to modify the merged bean definition.
		synchronized (mbd.postProcessingLock) {
			if (!mbd.postProcessed) {
				try {
					// 收集注解
					// BeanPostProcessor典型应用
					// CommonAnnotationBeanPostProcessor 支持了@PostContructor @PreDestroy @Resource
					// AutowiredAnnotationBeanPostProcessor 支持@Autowired @value 注解
					applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
				}
				catch (Throwable ex) {
					throw new BeanCreationException(mbd.getResourceDescription(), beanName,
							"Post-processing of merged bean definition failed", ex);
				}
				mbd.postProcessed = true;
			}
		}

		// Eagerly cache singletons to be able to resolve circular references
		// even when triggered by lifecycle interfaces like BeanFactoryAware.
		boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
				isSingletonCurrentlyInCreation(beanName));
		if (earlySingletonExposure) {
			if (logger.isTraceEnabled()) {
				logger.trace("Eagerly caching bean '" + beanName +
						"' to allow for resolving potential circular references");
			}
			addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
		}

		// Initialize the bean instance.
		Object exposedObject = bean;
		try {
			// 属性赋值
			populateBean(beanName, mbd, instanceWrapper);
			// 初始化bean
			exposedObject = initializeBean(beanName, exposedObject, mbd);
		}
		catch (Throwable ex) {
			if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
				throw (BeanCreationException) ex;
			}
			else {
				throw new BeanCreationException(
						mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
			}
		}

		if (earlySingletonExposure) {
			Object earlySingletonReference = getSingleton(beanName, false);
			if (earlySingletonReference != null) {
				if (exposedObject == bean) {
					exposedObject = earlySingletonReference;
				}
				else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
					String[] dependentBeans = getDependentBeans(beanName);
					Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
					for (String dependentBean : dependentBeans) {
						if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
							actualDependentBeans.add(dependentBean);
						}
					}
					if (!actualDependentBeans.isEmpty()) {
						throw new BeanCurrentlyInCreationException(beanName,
								"Bean with name '" + beanName + "' has been injected into other beans [" +
								StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
								"] in its raw version as part of a circular reference, but has eventually been " +
								"wrapped. This means that said other beans do not use the final version of the " +
								"bean. This is often the result of over-eager type matching - consider using " +
								"'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
					}
				}
			}
		}

		// Register bean as disposable.
		try {
			registerDisposableBeanIfNecessary(beanName, bean, mbd);
		}
		catch (BeanDefinitionValidationException ex) {
			throw new BeanCreationException(
					mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
		}

		return exposedObject;
	}

createBeanInstance上一篇已经讲完，完成bean的创建，创建完后，bean只是在堆内存中申请了一块内存空间，还没有对其属性赋值，而在属性赋值前，优先收集标注了注解的属性，收集过程在applyMergedBeanDefinitionPostProcessors方法中完成，进入该方法：

protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) {
		// 遍历当前类中的所有BeanPostProcessors
		for (BeanPostProcessor bp : getBeanPostProcessors()) {
			if (bp instanceof MergedBeanDefinitionPostProcessor) {
				MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
				bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);
			}
		}
	}

遍历当前类中的实现了BeanPostProcessor接口的类，再次进入postProcessMergedBeanDefinition方法，会看到有几个典型的实现类，首先是 CommonAnnotationBeanPostProcessor类，这个类完成了@Resource注解的属性或者方法的收集，这个类还对@PostConstruct和@PreDestory支持。具体的收集过程如下：

	public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
		// 扫描@PostConstructor @PreDestroy
		super.postProcessMergedBeanDefinition(beanDefinition, beanType, beanName);
		// 扫描属性与方法上的@Resource注解，收集到InjectionMetadata容器中
		InjectionMetadata metadata = findResourceMetadata(beanName, beanType, null);
		metadata.checkConfigMembers(beanDefinition);
	}

回到CommonAnnotationBeanPostProcessor类的构造方法，完成@PostConstruct和@PreDestory注解的设值，分别塞到initAnnotationType与destroyAnnotationType属性中：

	public CommonAnnotationBeanPostProcessor() {
		setOrder(Ordered.LOWEST_PRECEDENCE - 3);
		setInitAnnotationType(PostConstruct.class);
		setDestroyAnnotationType(PreDestroy.class);
		ignoreResourceType("javax.xml.ws.WebServiceContext");
	}

点击进入其父类InitDestroyAnnotationBeanPostProcessor的postProcessMergedBeanDefinition方法

	public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
		LifecycleMetadata metadata = findLifecycleMetadata(beanType);
		metadata.checkConfigMembers(beanDefinition);
	}

点击findLifecycleMetadata进入方法：

	private LifecycleMetadata findLifecycleMetadata(Class<?> clazz) {
		if (this.lifecycleMetadataCache == null) {
			// Happens after deserialization, during destruction...
			return buildLifecycleMetadata(clazz);
		}
		// Quick check on the concurrent map first, with minimal locking.
		LifecycleMetadata metadata = this.lifecycleMetadataCache.get(clazz);
		if (metadata == null) {
			synchronized (this.lifecycleMetadataCache) {
				metadata = this.lifecycleMetadataCache.get(clazz);
				if (metadata == null) {
					// 构建生命周期相关的元数据
					metadata = buildLifecycleMetadata(clazz);
					this.lifecycleMetadataCache.put(clazz, metadata);
				}
				return metadata;
			}
		}
		return metadata;
        }

再次进入构建生命周期相关的元数据的方法buildLifecycleMetadata:

	private LifecycleMetadata buildLifecycleMetadata(final Class<?> clazz) {
		if (!AnnotationUtils.isCandidateClass(clazz, Arrays.asList(this.initAnnotationType, this.destroyAnnotationType))) {
			return this.emptyLifecycleMetadata;
		}

		List<LifecycleElement> initMethods = new ArrayList<>();
		List<LifecycleElement> destroyMethods = new ArrayList<>();
		Class<?> targetClass = clazz;

		do {
			final List<LifecycleElement> currInitMethods = new ArrayList<>();
			final List<LifecycleElement> currDestroyMethods = new ArrayList<>();
			//遍历类中的方法，找到@PostConstruct注解的方法
			ReflectionUtils.doWithLocalMethods(targetClass, method -> {
				if (this.initAnnotationType != null && method.isAnnotationPresent(this.initAnnotationType)) {
					LifecycleElement element = new LifecycleElement(method);
					currInitMethods.add(element);
					if (logger.isTraceEnabled()) {
						logger.trace("Found init method on class [" + clazz.getName() + "]: " + method);
					}
				}
				//遍历类中的方法，找到@PreDestroy注解的方法
				if (this.destroyAnnotationType != null && method.isAnnotationPresent(this.destroyAnnotationType)) {
					currDestroyMethods.add(new LifecycleElement(method));
					if (logger.isTraceEnabled()) {
						logger.trace("Found destroy method on class [" + clazz.getName() + "]: " + method);
					}
				}
			});
			// @PostConstruct注解的方法加到initMethods
			initMethods.addAll(0, currInitMethods);
			// @PreDestroy注解的方法加到destroyMethods
			destroyMethods.addAll(currDestroyMethods);
			targetClass = targetClass.getSuperclass();
		}
		while (targetClass != null && targetClass != Object.class);

		return (initMethods.isEmpty() && destroyMethods.isEmpty() ? this.emptyLifecycleMetadata :
				new LifecycleMetadata(clazz, initMethods, destroyMethods));
	}

循环遍历类中的所有的方法，判断方法上是否有@PostConstruct注解如果有的话加入到initMethods集合，判断方法上是否有@PreDestroy注解，如果有加入到destroyMethods集合中去。

3.2 收集@Resource注解的属性与方法

进入上述findResourceMetadata方法：

	private InjectionMetadata findResourceMetadata(String beanName, final Class<?> clazz, @Nullable PropertyValues pvs) {
		// Fall back to class name as cache key, for backwards compatibility with custom callers.
		String cacheKey = (StringUtils.hasLength(beanName) ? beanName : clazz.getName());
		// 查看缓存里面有没有InjectionMetadata实例.
		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);
					}
					// 构建@Resource元数据
					metadata = buildResourceMetadata(clazz);
					this.injectionMetadataCache.put(cacheKey, metadata);
				}
			}
		}
		return metadata;
	}

step1:看缓存里面有没有 InjectionMetadata 对象；

step2:构建@Resource元数据；

再次进入buildResourceMetadata方法：

	private InjectionMetadata buildResourceMetadata(final Class<?> clazz) {
		if (!AnnotationUtils.isCandidateClass(clazz, resourceAnnotationTypes)) {
			return InjectionMetadata.EMPTY;
		}

		List<InjectionMetadata.InjectedElement> elements = new ArrayList<>();
		Class<?> targetClass = clazz;

		do {
			final List<InjectionMetadata.InjectedElement> currElements = new ArrayList<>();
			// 遍历所有field，判断有没有Resource注解
			ReflectionUtils.doWithLocalFields(targetClass, field -> {
				if (webServiceRefClass != null && field.isAnnotationPresent(webServiceRefClass)) {
					if (Modifier.isStatic(field.getModifiers())) {
						throw new IllegalStateException("@WebServiceRef annotation is not supported on static fields");
					}
					currElements.add(new WebServiceRefElement(field, field, null));
				}
				else if (ejbClass != null && field.isAnnotationPresent(ejbClass)) {
					if (Modifier.isStatic(field.getModifiers())) {
						throw new IllegalStateException("@EJB annotation is not supported on static fields");
					}
					currElements.add(new EjbRefElement(field, field, null));
				}
				else if (field.isAnnotationPresent(Resource.class)) {
					if (Modifier.isStatic(field.getModifiers())) {
						throw new IllegalStateException("@Resource annotation is not supported on static fields");
					}
					if (!this.ignoredResourceTypes.contains(field.getType().getName())) {
						currElements.add(new ResourceElement(field, field, null));
					}
				}
			});
			// 遍历所有方法，判断有没有@Resource注解
			ReflectionUtils.doWithLocalMethods(targetClass, method -> {
				Method bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
				if (!BridgeMethodResolver.isVisibilityBridgeMethodPair(method, bridgedMethod)) {
					return;
				}
				if (method.equals(ClassUtils.getMostSpecificMethod(method, clazz))) {
					if (webServiceRefClass != null && bridgedMethod.isAnnotationPresent(webServiceRefClass)) {
						if (Modifier.isStatic(method.getModifiers())) {
							throw new IllegalStateException("@WebServiceRef annotation is not supported on static methods");
						}
						if (method.getParameterCount() != 1) {
							throw new IllegalStateException("@WebServiceRef annotation requires a single-arg method: " + method);
						}
						PropertyDescriptor pd = BeanUtils.findPropertyForMethod(bridgedMethod, clazz);
						currElements.add(new WebServiceRefElement(method, bridgedMethod, pd));
					}
					else if (ejbClass != null && bridgedMethod.isAnnotationPresent(ejbClass)) {
						if (Modifier.isStatic(method.getModifiers())) {
							throw new IllegalStateException("@EJB annotation is not supported on static methods");
						}
						if (method.getParameterCount() != 1) {
							throw new IllegalStateException("@EJB annotation requires a single-arg method: " + method);
						}
						PropertyDescriptor pd = BeanUtils.findPropertyForMethod(bridgedMethod, clazz);
						currElements.add(new EjbRefElement(method, bridgedMethod, pd));
					}
					else if (bridgedMethod.isAnnotationPresent(Resource.class)) {
						if (Modifier.isStatic(method.getModifiers())) {
							throw new IllegalStateException("@Resource annotation is not supported on static methods");
						}
						Class<?>[] paramTypes = method.getParameterTypes();
						if (paramTypes.length != 1) {
							throw new IllegalStateException("@Resource annotation requires a single-arg method: " + method);
						}
						if (!this.ignoredResourceTypes.contains(paramTypes[0].getName())) {
							PropertyDescriptor pd = BeanUtils.findPropertyForMethod(bridgedMethod, clazz);
							currElements.add(new ResourceElement(method, bridgedMethod, pd));
						}
					}
				}
			});

			elements.addAll(0, currElements);
			targetClass = targetClass.getSuperclass();
		}
		while (targetClass != null && targetClass != Object.class);

		return InjectionMetadata.forElements(elements, clazz);
	}

step1:从类中获取所有 Field 对象，循环 field 对象，判断 field 有没有@Resource 注解，如果有注解封装成 ResourceElement 对象；

step2:从类中获取所有 Method对象，循环 Method对象，判断 Method有没有@Resource 注解，如果有注解封装成 ResourceElement 对象；

step3:最终把两个 field 和 Method 封装的对象集合封装到 InjectionMetadata 对象中。

3.3 @Autowired注解的属性与方法收集

AutowiredAnnotationBeanPostProcessor类对@Autowired和@Value注解的属性和方法的收集，收集支持的注解类型可以在构造函数或者 Static 静态块中找。收集过程基本上跟@Resource注解的收集差不多。下面先看AutowiredAnnotationBeanPostProcessor的构造函数：

	public AutowiredAnnotationBeanPostProcessor() {
		this.autowiredAnnotationTypes.add(Autowired.class);
		this.autowiredAnnotationTypes.add(Value.class);
		try {
			this.autowiredAnnotationTypes.add((Class<? extends Annotation>)
					ClassUtils.forName("javax.inject.Inject", AutowiredAnnotationBeanPostProcessor.class.getClassLoader()));
			logger.trace("JSR-330 'javax.inject.Inject' annotation found and supported for autowiring");
		}
		catch (ClassNotFoundException ex) {
			// JSR-330 API not available - simply skip.
		}
        }

收集了@Autowired和@Value注解并设置到autowiredAnnotationTypes类型中。后面流程与@Resource收集一样，也是收集Field和Method上面的注解，然后放到InjectionMetadata对象中。

	private InjectionMetadata buildAutowiringMetadata(final Class<?> clazz) {
		if (!AnnotationUtils.isCandidateClass(clazz, this.autowiredAnnotationTypes)) {
			return InjectionMetadata.EMPTY;
		}

		List<InjectionMetadata.InjectedElement> elements = new ArrayList<>();
		Class<?> targetClass = clazz;

		do {
			final List<InjectionMetadata.InjectedElement> currElements = new ArrayList<>();
                        // 循环收集Field上面是否有@Autowired注解
			ReflectionUtils.doWithLocalFields(targetClass, field -> {
				MergedAnnotation<?> ann = findAutowiredAnnotation(field);
				if (ann != null) {
					if (Modifier.isStatic(field.getModifiers())) {
						if (logger.isInfoEnabled()) {
							logger.info("Autowired annotation is not supported on static fields: " + field);
						}
						return;
					}
					boolean required = determineRequiredStatus(ann);
					currElements.add(new AutowiredFieldElement(field, required));
				}
			});
                        // 循环收集Method上面是否有@Autowired注解
			ReflectionUtils.doWithLocalMethods(targetClass, method -> {
				Method bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
				if (!BridgeMethodResolver.isVisibilityBridgeMethodPair(method, bridgedMethod)) {
					return;
				}
				MergedAnnotation<?> ann = findAutowiredAnnotation(bridgedMethod);
				if (ann != null && method.equals(ClassUtils.getMostSpecificMethod(method, clazz))) {
					if (Modifier.isStatic(method.getModifiers())) {
						if (logger.isInfoEnabled()) {
							logger.info("Autowired annotation is not supported on static methods: " + method);
						}
						return;
					}
					if (method.getParameterCount() == 0) {
						if (logger.isInfoEnabled()) {
							logger.info("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));
				}
			});
                        // 放入容器elements，而elements本身是InjectionMetadata类型下的InjectedElement属性
			elements.addAll(0, currElements);
			targetClass = targetClass.getSuperclass();
		}
		while (targetClass != null && targetClass != Object.class);

		return InjectionMetadata.forElements(elements, clazz);
	}

3.4 属性赋值

收集完@Resource和@Autowired注解以后就开始依赖注入，进入populateBean方法：

	protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
		if (bw == null) {
			if (mbd.hasPropertyValues()) {
				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.
		if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof InstantiationAwareBeanPostProcessor) {
					InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
					if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
						return;
					}
				}
			}
		}

		PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);

		int resolvedAutowireMode = mbd.getResolvedAutowireMode();
		if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
			MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
			// Add property values based on autowire by name if applicable.
			if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
				autowireByName(beanName, mbd, bw, newPvs);
			}
			// Add property values based on autowire by type if applicable.
			if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
				autowireByType(beanName, mbd, bw, newPvs);
			}
			pvs = newPvs;
		}

		boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
		boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);

		PropertyDescriptor[] filteredPds = null;
		if (hasInstAwareBpps) {
			if (pvs == null) {
				pvs = mbd.getPropertyValues();
			}
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof InstantiationAwareBeanPostProcessor) {
					InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
					// 依赖注入的过程，@Autowired支持 @Resource支持
					PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
					if (pvsToUse == null) {
						if (filteredPds == null) {
							filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
						}
						pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
						if (pvsToUse == null) {
							return;
						}
					}
					pvs = pvsToUse;
				}
			}
		}
		if (needsDepCheck) {
			if (filteredPds == null) {
				filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
			}
			checkDependencies(beanName, mbd, filteredPds, pvs);
		}

		if (pvs != null) {
			applyPropertyValues(beanName, mbd, bw, pvs);
		}
	}

该方法的核心工作就是完成依赖注入，进入postProcessProperties方法：

        public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
		InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);
		try {
			// 依赖注入
			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;
	}

最后通过metadata.inject方法把容器中收集的属性注入：

	public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
		Collection<InjectedElement> checkedElements = this.checkedElements;
		Collection<InjectedElement> elementsToIterate =
				(checkedElements != null ? checkedElements : this.injectedElements);
		if (!elementsToIterate.isEmpty()) {
			for (InjectedElement element : elementsToIterate) {
				if (logger.isTraceEnabled()) {
					logger.trace("Processing injected element of bean '" + beanName + "': " + element);
				}
				// 循环调用每个方法依赖一次处理
				element.inject(target, beanName, pvs);
			}
		}
	}

点击进入inject方法：

		protected void inject(Object target, @Nullable String requestingBeanName, @Nullable PropertyValues pvs)
				throws Throwable {

			if (this.isField) {
				Field field = (Field) this.member;
				ReflectionUtils.makeAccessible(field);
				// 设置属性,getResourceToInject会触发getBean
				field.set(target, getResourceToInject(target, requestingBeanName));
			}
			else {
				if (checkPropertySkipping(pvs)) {
					return;
				}
				try {
					Method method = (Method) this.member;
					ReflectionUtils.makeAccessible(method);
					// 设置方法
					method.invoke(target, getResourceToInject(target, requestingBeanName));
				}
				catch (InvocationTargetException ex) {
					throw ex.getTargetException();
				}
			}
		}

看到属性与方法通过反射的注入到所需的实例中，如果注入的是引用类型，会通过调用getResourceToInject方法优先拿到引用类型的实例，底层是通过BeanFactory.getBean方式拿到应用的属性的:

		protected Object getResourceToInject(Object target, @Nullable String requestingBeanName) {
			if (StringUtils.hasLength(this.beanName)) {
				if (beanFactory != null && beanFactory.containsBean(this.beanName)) {
					// Local match found for explicitly specified local bean name.
                                        // 通过getBean方式拿引用类型的值
					Object bean = beanFactory.getBean(this.beanName, this.lookupType);
					if (requestingBeanName != null && beanFactory instanceof ConfigurableBeanFactory) {
						((ConfigurableBeanFactory) beanFactory).registerDependentBean(this.beanName, requestingBeanName);
					}
					return bean;
				}
				else if (this.isDefaultName && !StringUtils.hasLength(this.mappedName)) {
					throw new NoSuchBeanDefinitionException(this.beanName,
							"Cannot resolve 'beanName' in local BeanFactory. Consider specifying a general 'name' value instead.");
				}
			}

4. 总结

本篇讲述了实例化后属性的收集与赋值过程，通过典型的BeanPostProccessor应用，完成相关注解的收集，并完成依赖注入，最终完成属性赋值，后续将继续分析初始化流程。