基于springboot bean的实例化过程和属性注入过程

目录

• bean的实例化过程和属性注入过程
• bean实例化流程说明

// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.新建beanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
   // Allows post-processing of the bean factory in context subclasses.
   postProcessBeanFactory(beanFactory);
   // Invoke factory processors registered as beans in the context.
   // 加载实现beanFactoryPostProcessor的bean，bean定义的时候执行
   invokeBeanFactoryPostProcessors(beanFactory);
   // Register bean processors that intercept bean creation.
   // 加载实现了beanPostProcessor，在bean实例化前、后执行
   registerBeanPostProcessors(beanFactory);
   // Initialize message source for this context.
   initMessageSource();
   // Initialize event multicaster for this context.
   initApplicationEventMulticaster();
   // Initialize other special beans in specific context subclasses.
   onRefresh();
   // Check for listener beans and register them.
   registerListeners();
   // Instantiate all remaining (non-lazy-init) singletons.
   //实例化非懒加载的bean、bean封装、属性注入、注解注入(主要使用BeanPostProcessor或子类实现)等
   finishBeanFactoryInitialization(beanFactory);
   // Last step: publish corresponding event.
   finishRefresh();

// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();

if (sharedInstance != null && args == null) {
   if (logger.isDebugEnabled()) {
      if (isSingletonCurrentlyInCreation(beanName)) {
         logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
               "' that is not fully initialized yet - a consequence of a circular reference");
      }
      else {
         logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
      }
   }
   bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);

BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
   // Not found -> check parent.
   String nameToLookup = originalBeanName(name);
   if (parentBeanFactory instanceof AbstractBeanFactory) {
      return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
            nameToLookup, requiredType, args, typeCheckOnly);
   }
   else 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);
   }
}

//mark 给此bean 马克一下。防止重复创建
if (!typeCheckOnly) {
   markBeanAsCreated(beanName);
}
try {
   final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
   checkMergedBeanDefinition(mbd, beanName, args);
   // Guarantee initialization of beans that the current bean depends on.
   String[] dependsOn = mbd.getDependsOn();
   if (dependsOn != null) {
      for (String dep : dependsOn) {
         if (isDependent(beanName, dep)) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                  "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
         }
         registerDependentBean(dep, beanName);
         getBean(dep);
      }
   }

// Create bean instance.
if (mbd.isSingleton()) {
   sharedInstance = getSingleton(beanName, () -> {
      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);

// Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
   try {
      T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
      if (convertedBean == null) {
         throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
      }
      return convertedBean;
   }
   catch (TypeMismatchException ex) {
      if (logger.isDebugEnabled()) {
         logger.debug("Failed to convert bean '" + name + "' to required type '" +
               ClassUtils.getQualifiedName(requiredType) + "'", ex);
      }
      throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
   }
}

try {
   // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
   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);
}

try {
   Object beanInstance = doCreateBean(beanName, mbdToUse, args);
   if (logger.isDebugEnabled()) {
      logger.debug("Finished creating instance of bean '" + beanName + "'");
   }
   return beanInstance;
}

// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
   instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
   instanceWrapper = createBeanInstance(beanName, mbd, args);
}

// Need to determine the constructor...
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null ||
      mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
      mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
   return autowireConstructor(beanName, mbd, ctors, args);
}
// No special handling: simply use no-arg constructor.
return instantiateBean(beanName, mbd);

Object exposedObject = bean;
try {
   populateBean(beanName, mbd, instanceWrapper);
   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 (hasInstAwareBpps || needsDepCheck) {
   if (pvs == null) {
      pvs = mbd.getPropertyValues();
   }
   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);
   }
}

// 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);
         }
         metadata = buildAutowiringMetadata(clazz);
         this.injectionMetadataCache.put(cacheKey, metadata);
      }
   }
} 
return metadata;

// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
   if (!mbd.postProcessed) {
      try {
         //通过 BeanPostProcessor将需要注解的元数据 放到Map中
         applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
      }
      catch (Throwable ex) {
         throw new BeanCreationException(mbd.getResourceDescription(), beanName,
               "Post-processing of merged bean definition failed", ex);
      }
      mbd.postProcessed = true;
   }
}

if (this.isField) {
   Field field = (Field) this.member;
   ReflectionUtils.makeAccessible(field);
   field.set(target, getResourceToInject(target, requestingBeanName));
}
else {
   if (checkPropertySkipping(pvs)) {
      return;
   }
   try {
      Method method = (Method) this.member;
      ReflectionUtils.makeAccessible(method);
      method.invoke(target, getResourceToInject(target, requestingBeanName));
   }
   catch (InvocationTargetException ex) {
      throw ex.getTargetException();
   }
}

if (System.getSecurityManager() != null) {
   AccessControlContext acc = getAccessControlContext();
   try {
      object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) factory::getObject, acc);
   }
   catch (PrivilegedActionException pae) {
      throw pae.getException();
   }
}
else {
   //从FactoryBean实现bean中getObejct获取到bean
   object = factory.getObject();
}

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
        // Initialize conversion service for this context.
        if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
                beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
            beanFactory.setConversionService(
                    beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
        }
        // Register a default embedded value resolver if no bean post-processor
        // (such as a PropertyPlaceholderConfigurer bean) registered any before:
        // at this point, primarily for resolution in annotation attribute values.
        if (!beanFactory.hasEmbeddedValueResolver()) {
            beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
        }
        // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
        String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
        for (String weaverAwareName : weaverAwareNames) {
            getBean(weaverAwareName);
        }
        // Stop using the temporary ClassLoader for type matching.
        beanFactory.setTempClassLoader(null);
        // Allow for caching all bean definition metadata, not expecting further changes.
        beanFactory.freezeConfiguration();
        // Instantiate all remaining (non-lazy-init) singletons.
        beanFactory.preInstantiateSingletons();
    }