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获取bean

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获取bean

在进行获取bean的时候使用getBean方法来进行获取，那么就从getBean来作为入口，看一下获取bean的流程

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ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
Car car = (Car) context.getBean("car");
System.out.println(car);
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// org.springframework.beans.factory.support.AbstractBeanFactory#getBean(java.lang.String)
public Object getBean(String name) throws BeansException {
   return doGetBean(name, null, null, false);
}

doGetBean方法

这个方法比较长，分为很多步

  • transformedBeanName方法，对传入的beanName进行转换，因为传入的name不一定是beanName，也可能是FactoryBean，检查name的前缀是不是&，如果是别名的话，从aliasMap中获取真正的beanName
  • getSingleton方法，从缓存singletonObjects中加载单例，如果加载不成功尝试从singletonFactories中加载
  • getObjectForBeanInstance方法，进行bean的实例化，缓存中记录的是最原始的bean状态，对于FactoryBean需要再次进行处理
  • isPrototypeCurrentlyInCreation方法，原型的依赖检查
  • parentBeanFactory != null && !containsBeanDefinition(beanName)，如果parentBeanFactory不为null，且当前加载的XML配置文件中不包含beanName，则会去parentBeanFactory中进行尝试获取
  • mbd.getDependsOn()，寻找依赖
  • 针对不同的scope的bean来进行创建
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// org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean
// 实际获取Bean的方法
protected <T> T doGetBean(
      final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
      throws BeansException {
// 获取对应的beanName，可能是FactoryBean，可能是使用别名的  FactoryBean的前缀是&    beanName.startsWith(BeanFactory.FACTORY_BEAN_PREFIX
   final String beanName = transformedBeanName(name);
   Object bean;

   // Eagerly check singleton cache for manually registered singletons.
  // 检查缓存中或者实例工厂中是否存在该bean，处理已经被创建过的单例bean，这种bean不需要重复创建
  // 在创建单例bean的时候会存在依赖注入的情况，为了避免循环依赖，spring创建bean的原则是不等bean创建完成就会将创建bean的ObjectFactory提前曝光，将ObjectFactory加入到缓存中，一旦下一个bean创建时需要依赖上一个bean则直接使用ObjectFactory
   Object sharedInstance = getSingleton(beanName);
   if (sharedInstance != null && args == null) {
      
     // 返回对应的bean，如果是FactoryBean的话是通过指定方法来创建bean
      bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
   }

   else {
      // Fail if we're already creating this bean instance:
      // We're assumably within a circular reference.
     // 只有单例才会解决循环依赖，原型如果存在循环依赖的话就会抛出异常
      if (isPrototypeCurrentlyInCreation(beanName)) {
         throw new BeanCurrentlyInCreationException(beanName);
      }

      // Check if bean definition exists in this factory.
     // 检查ioc容器中是否存在BeanDefinition，检查是否能在当前的BeanFactory中取得需要的bean
      BeanFactory parentBeanFactory = getParentBeanFactory();
     // 如果当前的工厂中取不到，则到父BeanFactory中去取
      if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
         // Not found -> check parent.
         String nameToLookup = originalBeanName(name);
         if (args != null) {
            // Delegation to parent with explicit args.
            return (T) parentBeanFactory.getBean(nameToLookup, args);
         }
         else {
            // No args -> delegate to standard getBean method.
            return parentBeanFactory.getBean(nameToLookup, requiredType);
         }
      }
            // 如果不仅仅做类型检查，则是需要创建bean
      if (!typeCheckOnly) {
         markBeanAsCreated(beanName);
      }

      try {
        // 根据bean的名字取得BeanDefinition
         final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
         checkMergedBeanDefinition(mbd, beanName, args);

         // Guarantee initialization of beans that the current bean depends on.
        // 获取当前Bean所依赖的Bean
         String[] dependsOn = mbd.getDependsOn();
         if (dependsOn != null) {
           // 递归查找依赖的bean
            for (String dep : dependsOn) {
               if (isDependent(beanName, dep)) {
                  throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
               }
              // 缓存依赖调用
               registerDependentBean(dep, beanName);
               getBean(dep);
            }
         }

         // Create bean instance.
        // 创建单例bean
         if (mbd.isSingleton()) {
            sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
               @Override
               public Object getObject() throws BeansException {
                  try {
                    // 创建bean
                     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);
         }
        // 创建prototype bean
         else if (mbd.isPrototype()) {
            // It's a prototype -> create a new instance.
            Object prototypeInstance = null;
            try {
               beforePrototypeCreation(beanName);
               prototypeInstance = createBean(beanName, mbd, args);
            }
            finally {
               afterPrototypeCreation(beanName);
            }
            bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
         }

         else {
           // 其他scope的bean
            String scopeName = mbd.getScope();
            final Scope scope = this.scopes.get(scopeName);
            if (scope == null) {
               throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
            }
            try {
               Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
                  @Override
                  public Object getObject() throws BeansException {
                     beforePrototypeCreation(beanName);
                     try {
                        return createBean(beanName, mbd, args);
                     }
                     finally {
                        afterPrototypeCreation(beanName);
                     }
                  }
               });
               bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
            }
            catch (IllegalStateException ex) {
               throw new BeanCreationException(beanName,
                     "Scope '" + scopeName + "' is not active for the current thread; consider " +
                     "defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                     ex);
            }
         }
      }
      catch (BeansException ex) {
         cleanupAfterBeanCreationFailure(beanName);
         throw ex;
      }
   }

   // Check if required type matches the type of the actual bean instance.
  // 检查需要的类型是否符合bean的实际类型
   if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
      try {
         return getTypeConverter().convertIfNecessary(bean, requiredType);
      }
      catch (TypeMismatchException ex) {
         
         throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
      }
   }
   return (T) bean;
}

getSingleton方法

从缓存singletonObjects中加载单例，如果加载不成功尝试从singletonFactories中加载

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/** Cache of singleton objects: bean name --> bean instance */
// 一级缓存 存放的是 beanName,bean实例
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(256);

/** Cache of singleton factories: bean name --> ObjectFactory */
// 三级缓存，存放的是beanName,ObjectFactory
private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<String, ObjectFactory<?>>(16);

/** Cache of early singleton objects: bean name --> bean instance */
// 二级缓存，存放的是beanName,bean实例，此时存放的是早期的bean，存放的并不一定是完整的，在创建过程中就加入到earlySingletonObjects中了
private final Map<String, Object> earlySingletonObjects = new HashMap<String, Object>(16);

三级缓存解决循环依赖

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// allowEarlyReference是true，表示允许早期依赖
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
  // 从singletonObjects缓存中取
  // singletonObjects中存的是beanName和bean实例
  // singletonObjects是一级缓存
   Object singletonObject = this.singletonObjects.get(beanName);
  // 缓存中没有，且当前bean正在创建
   if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
     // 锁定全局变量进行处理
      synchronized (this.singletonObjects) {
        // 如果该bean正在进行加载则不进行处理，直接返回
        // earlySingletonObjects中存的是beanName和bean实例,但是与singletonObjects不同的是,存储的是还没进行属性注入操作的Bean的实例，，目的是为了监测循环引用
        // earlySingletonObjects是二级缓存
         singletonObject = this.earlySingletonObjects.get(beanName);
         if (singletonObject == null && allowEarlyReference) {
           // 从singletonFactories中获取，对于某些方法需要提前进行初始化时则会调用addSingletonFactory方法将对应的ObjectFactory初始化策略存在singletonFactories中
           // singletonFactories中存的是beanName和创建bean的ObjectFactory工厂
           // singletonFactories是三级缓存
            ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
            if (singletonFactory != null) {
              // 调用ObjectFactory的getObject方法
               singletonObject = singletonFactory.getObject();
              // 记录在缓存earlySingletonObjects中，earlySingletonObjects和singletonFactories互斥
               this.earlySingletonObjects.put(beanName, singletonObject);
               this.singletonFactories.remove(beanName);
            }
         }
      }
   }
   return (singletonObject != NULL_OBJECT ? singletonObject : null);
}

getObjectForBeanInstance获取bean实例

主要是为了解决FactoryBean的情况

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protected Object getObjectForBeanInstance(
      Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

   // Don't let calling code try to dereference the factory if the bean isn't a factory.
  // 如果指定的name是以&为前缀，但是却不是FactoryBean实例，则抛出异常
   if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
      throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
   }

   // Now we have the bean instance, which may be a normal bean or a FactoryBean.
   // If it's a FactoryBean, we use it to create a bean instance, unless the
   // caller actually wants a reference to the factory.
  // 正常bean则直接返回
   if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
      return beanInstance;
   }
// 到这里就都是FactoryBean
   Object object = null;
   if (mbd == null) {
     // 从缓存中加载bean
      object = getCachedObjectForFactoryBean(beanName);
   }
  // 缓存中没有
   if (object == null) {
      // Return bean instance from factory.
      FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
      // Caches object obtained from FactoryBean if it is a singleton.
      if (mbd == null && containsBeanDefinition(beanName)) {
         mbd = getMergedLocalBeanDefinition(beanName);
      }
     // 判断是用户自定义的还是应用程序本身的
      boolean synthetic = (mbd != null && mbd.isSynthetic());
      object = getObjectFromFactoryBean(factory, beanName, !synthetic);
   }
   return object;
}
getObjectFromFactoryBean

从FactoryBean获取bean对象

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protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
  // 为单例模式且缓存中存在
   if (factory.isSingleton() && containsSingleton(beanName)) {
      synchronized (getSingletonMutex()) {
        // 从缓存中获取指定的FactoryBean
         Object object = this.factoryBeanObjectCache.get(beanName);
         if (object == null) { // 对象为null，则从FactoryBean中获取
            object = doGetObjectFromFactoryBean(factory, beanName);
            // Only post-process and store if not put there already during getObject() call above
            // (e.g. because of circular reference processing triggered by custom getBean calls)
            Object alreadyThere = this.factoryBeanObjectCache.get(beanName);
            if (alreadyThere != null) {
               object = alreadyThere;
            }
            else {
               if (object != null && shouldPostProcess) {
                  try {
                    // 调用ObjectFactory的后置处理器
                     object = postProcessObjectFromFactoryBean(object, beanName);
                  }
                  catch (Throwable ex) {
                     throw new BeanCreationException(beanName,
                           "Post-processing of FactoryBean's singleton object failed", ex);
                  }
               }
               this.factoryBeanObjectCache.put(beanName, (object != null ? object : NULL_OBJECT));
            }
         }
         return (object != NULL_OBJECT ? object : null);
      }
   }
   else {
      Object object = doGetObjectFromFactoryBean(factory, beanName);
      if (object != null && shouldPostProcess) {
         try {
            object = postProcessObjectFromFactoryBean(object, beanName);
         }
         catch (Throwable ex) {
            throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);
         }
      }
      return object;
   }
}
doGetObjectFromFactoryBean
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private Object doGetObjectFromFactoryBean(final FactoryBean<?> factory, final String beanName)
      throws BeanCreationException {

   Object object;
   try {
     object = factory.getObject();
   }
   catch (FactoryBeanNotInitializedException ex) {
      throw new BeanCurrentlyInCreationException(beanName, ex.toString());
   }
   catch (Throwable ex) {
      throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
   }

   // Do not accept a null value for a FactoryBean that's not fully
   // initialized yet: Many FactoryBeans just return null then.
   if (object == null && isSingletonCurrentlyInCreation(beanName)) {
      throw new BeanCurrentlyInCreationException(
            beanName, "FactoryBean which is currently in creation returned null from getObject");
   }
   return object;
}
postProcessObjectFromFactoryBean
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// org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#postProcessObjectFromFactoryBean
protected Object postProcessObjectFromFactoryBean(Object object, String beanName) {
   return applyBeanPostProcessorsAfterInitialization(object, beanName);
}

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
            throws BeansException {

        Object result = existingBean;
        for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
            result = beanProcessor.postProcessAfterInitialization(result, beanName);
            if (result == null) {
                return result;
            }
        }
        return result;
    }

createBean创建bean

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protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
   
   RootBeanDefinition mbdToUse = mbd;

   // Make sure bean class is actually resolved at this point, and
   // clone the bean definition in case of a dynamically resolved Class
   // which cannot be stored in the shared merged bean definition.
  // 根据设置的className来解析class
   Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
   if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
      mbdToUse = new RootBeanDefinition(mbd);
      mbdToUse.setBeanClass(resolvedClass);
   }

   // Prepare method overrides.
  // 准备方法覆盖
  // 在配置bean的时候配置lookup-method或者replace-method则会进行方法覆盖
   try {
      mbdToUse.prepareMethodOverrides();
   }
   catch (BeanDefinitionValidationException ex) {
      throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
            beanName, "Validation of method overrides failed", ex);
   }

   try {
      // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
     // BeanPostProcessors来返回代理代替真正的实例
      Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
      if (bean != null) {
         return bean;
      }
   }
   catch (Throwable ex) {
      throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
            "BeanPostProcessor before instantiation of bean failed", ex);
   }

  // 创建bean
   Object beanInstance = doCreateBean(beanName, mbdToUse, args);
   
   return beanInstance;
}
resolveBeforeInstantiation

后置处理器

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protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
   Object bean = null;
  // mbd.beforeInstantiationResolved为false
   if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
      // Make sure bean class is actually resolved at this point.
      if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
         Class<?> targetType = determineTargetType(beanName, mbd);
         if (targetType != null) {
           // 实例化前处理
            bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
            if (bean != null) {
              // 实例化后处理
               bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
            }
         }
      }
      mbd.beforeInstantiationResolved = (bean != null);
   }
   return bean;
}
applyBeanPostProcessorsBeforeInstantiation
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protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
   for (BeanPostProcessor bp : getBeanPostProcessors()) {
      if (bp instanceof InstantiationAwareBeanPostProcessor) {
         InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
         Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
         if (result != null) {
            return result;
         }
      }
   }
   return null;
}
applyBeanPostProcessorsAfterInitialization
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public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
      throws BeansException {

   Object result = existingBean;
   for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
      result = beanProcessor.postProcessAfterInitialization(result, beanName);
      if (result == null) {
         return result;
      }
   }
   return result;
}
doCreateBean
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protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
      throws BeanCreationException {

   // Instantiate the bean.
   BeanWrapper instanceWrapper = null;
  // 单例，从未完成的FactoryBean缓存中删除
   if (mbd.isSingleton()) {
      instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
   }
   if (instanceWrapper == null) {
     // 创建bean实例
      instanceWrapper = createBeanInstance(beanName, mbd, args);
   }
   final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
   Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
   mbd.resolvedTargetType = beanType;

   // Allow post-processors to modify the merged bean definition.
   synchronized (mbd.postProcessingLock) {
      if (!mbd.postProcessed) {
         try {
         // 处理@Value、@Autowried  调用AutowiredAnnotationBeanPostProcessor#postProcessMergedBeanDefinition处理@Autowried和@Value
            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.
  // 是否需要提前暴露    是单例 && 允许循环依赖 && 当前bean正在创建
   boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
         isSingletonCurrentlyInCreation(beanName));
   if (earlySingletonExposure) {
      
     // 在bean初始化完成前将创建实例的ObjectFactory加入singletonFactories中，以便于后期循环依赖使用bean
      addSingletonFactory(beanName, new ObjectFactory<Object>() {
         @Override
         public Object getObject() throws BeansException {
           // 对bean进行BeanPostProcessor后置处理  SmartInstantiationAwareBeanPostProcessor
           // AOP中的advice就是在这里处理的
            return getEarlyBeanReference(beanName, mbd, bean);
         }
      });
   }

   // Initialize the bean instance.
  // 初始化bean对象
   Object exposedObject = bean;
   try {
     // 对bean进行属性注入，在这里如果依赖于其他bean的话，会进行递归创建依赖bean
      populateBean(beanName, mbd, instanceWrapper);
      if (exposedObject != null) {
        // 调用初始化方法,如BeanNameAware#setBeanName，BeanClassLoaderAware#setBeanClassLoader，BeanFactoryAware#setBeanFactory，BeanPostProcessor处理器，InitializingBean#afterPropertiesSet， init-method
         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);
     // 在检测到有循环依赖的情况下earlySingletonReference不为null
      if (earlySingletonReference != null) {
        // exposedObject == bean表示没有在初始化方法中被改变
         if (exposedObject == bean) {
            exposedObject = earlySingletonReference;
         }
         else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
            String[] dependentBeans = getDependentBeans(beanName);
            Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
            for (String dependentBean : dependentBeans) {
               if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
                  actualDependentBeans.add(dependentBean);
               }
            }
           // bean创建后其所依赖的bean是已经被创建的，actualDependentBeans不为空表示当前bean创建后其所依赖的bean没有完全创建完，存在循环依赖
            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;
}
populateBean属性注入

依赖注入是在这里进行的

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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.
        // 没有可填充的属性
         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;
            }
         }
      }
   }

   int resolvedAutowireMode = mbd.getResolvedAutowireMode();
  // 解析autowired
   if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
      MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
      // Add property values based on autowire by name if applicable.
     // 根据名称自动注入
      if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
         autowireByName(beanName, mbd, bw, newPvs);
      }
      // Add property values based on autowire by type if applicable.
     // 根据类型自动注入
      if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
         autowireByType(beanName, mbd, bw, newPvs);
      }
      pvs = newPvs;
   }

   boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
   boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.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;
               pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
               if (pvs == null) {
                  return;
               }
            }
         }
      }
      if (needsDepCheck) {
         checkDependencies(beanName, mbd, filteredPds, pvs);
      }
   }
// 将属性应用到bean中
   applyPropertyValues(beanName, mbd, bw, pvs);
}
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