SpringBoot 中BeanDefinition究竟是什么时候被初始化成bean的（四）

喜欢ヅ旅行 2022-12-10 10:22 136阅读 0赞

1、前几篇文章详细讲到了类被加载到DefaultListableBeanFactory.beanDefinitionMap  
2、有的value是BeanDefinition ，有的是CGLIB对象  
问题来了，BeanDefinition等数据是什么时候被初始化的呢

[讲的有下面方法的入口][Link 1]

1.  org.springframework.context.support.AbstractApplicationContext\#refresh

@Override
    	public void refresh() throws BeansException, IllegalStateException {
    		synchronized (this.startupShutdownMonitor) {
    			// Prepare this context for refreshing.
    			prepareRefresh();
    
    			// Tell the subclass to refresh the internal bean factory.
    			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.
    				invokeBeanFactoryPostProcessors(beanFactory);
    
    				// Register bean processors that intercept bean creation.
    				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.
    				//初始化所有的单例对象，锚点一
    				finishBeanFactoryInitialization(beanFactory);
    
    				// Last step: publish corresponding event.
    				finishRefresh();
    			}
    
    			catch (BeansException ex) {
    				if (logger.isWarnEnabled()) {
    					logger.warn("Exception encountered during context initialization - " +
    							"cancelling refresh attempt: " + ex);
    				}
    
    				// Destroy already created singletons to avoid dangling resources.
    				destroyBeans();
    
    				// Reset 'active' flag.
    				cancelRefresh(ex);
    
    				// Propagate exception to caller.
    				throw ex;
    			}
    
    			finally {
    				// Reset common introspection caches in Spring's core, since we
    				// might not ever need metadata for singleton beans anymore...
    				resetCommonCaches();
    			}
    		}
    	}

**锚点一**

/**
    	 * Finish the initialization of this context's bean factory,
    	 * initializing all remaining singleton beans.
    	 */
    	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.
    		//初始化所有的单例
    		beanFactory.preInstantiateSingletons();
    	}

@Override
    	public void preInstantiateSingletons() throws BeansException {
    		if (logger.isTraceEnabled()) {
    			logger.trace("Pre-instantiating singletons in " + this);
    		}
    
    		// Iterate over a copy to allow for init methods which in turn register new bean definitions.
    		// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
    		List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
    
    		// Trigger initialization of all non-lazy singleton beans...
    		for (String beanName : beanNames) {
    			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
    			//判断不是抽象，是单例，不是懒加载
    			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
    			//是否是factoryBean
    				if (isFactoryBean(beanName)) {
    					Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
    					if (bean instanceof FactoryBean) {
    						final FactoryBean<?> factory = (FactoryBean<?>) bean;
    						boolean isEagerInit;
    						if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
    							isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
    											((SmartFactoryBean<?>) factory)::isEagerInit,
    									getAccessControlContext());
    						}
    						else {
    							isEagerInit = (factory instanceof SmartFactoryBean &&
    									((SmartFactoryBean<?>) factory).isEagerInit());
    						}
    						if (isEagerInit) {
    						//这个就算初始化bean了，，下文入口
    							getBean(beanName);
    						}
    					}
    				}
    				else {
    					getBean(beanName);
    				}
    			}
    		}
    
    		锚点二

**getBean(beanName);**  
下面的代码有没有好熟悉。这不正是[SpringMVC加载xml][SpringMVC_xml]的第六步嘛，以下的创建方法实际和mvc里面的是一模一样的，不了解的同学不访多看一遍。

protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
    		@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
    
    	final String beanName = transformedBeanName(name);
    	Object bean;
    
    	// Eagerly check singleton cache for manually registered singletons.
    	Object sharedInstance = getSingleton(beanName);
    	if (sharedInstance != null && args == null) {
    		if (logger.isTraceEnabled()) {
    			if (isSingletonCurrentlyInCreation(beanName)) {
    				logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
    						"' that is not fully initialized yet - a consequence of a circular reference");
    			}
    			else {
    				logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
    			}
    		}
    		bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
    									略
    									略
    
    			// Create bean instance.
    			if (mbd.isSingleton()) {
    				sharedInstance = getSingleton(beanName, () -> {
    					try {
    						//实际创建的执行者，下文入口
    						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);
    			}
    
    	}

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory\#doCreateBean

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
    			throws BeanCreationException {
    
    		// Instantiate the bean.
    		BeanWrapper instanceWrapper = null;
    		if (mbd.isSingleton()) {
    			instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
    		}
    		if (instanceWrapper == null) {
    		//创建类  锚点三
    			instanceWrapper = createBeanInstance(beanName, mbd, args);
    		}
    		final 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 {
    					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 {
    			//锚点四
    			populateBean(beanName, mbd, instanceWrapper);
    			//锚点五
    			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;
    	}

次方法执行完就意味着对象创建完成。

**锚点三**

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
    		try {
    			Object beanInstance;
    			final BeanFactory parent = this;
    			if (System.getSecurityManager() != null) {
    				beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
    						getInstantiationStrategy().instantiate(mbd, beanName, parent),
    						getAccessControlContext());
    			}
    			else {
    			//创建方法，下文入口
    				beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
    			}
    			BeanWrapper bw = new BeanWrapperImpl(beanInstance);
    			initBeanWrapper(bw);
    			return bw;
    		}
    		catch (Throwable ex) {
    			throw new BeanCreationException(
    					mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
    		}
    	}

@Override
    	public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
    		// Don't override the class with CGLIB if no overrides.
    		if (!bd.hasMethodOverrides()) {
    			Constructor<?> constructorToUse;
    			synchronized (bd.constructorArgumentLock) {
    				constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
    				if (constructorToUse == null) {
    					final Class<?> clazz = bd.getBeanClass();
    					if (clazz.isInterface()) {
    						throw new BeanInstantiationException(clazz, "Specified class is an interface");
    					}
    					try {
    						if (System.getSecurityManager() != null) {
    							constructorToUse = AccessController.doPrivileged(
    									(PrivilegedExceptionAction<Constructor<?>>) clazz::getDeclaredConstructor);
    						}
    						else {
    							constructorToUse = clazz.getDeclaredConstructor();
    						}
    						bd.resolvedConstructorOrFactoryMethod = constructorToUse;
    					}
    					catch (Throwable ex) {
    						throw new BeanInstantiationException(clazz, "No default constructor found", ex);
    					}
    				}
    			}
    			// 通过反射生成对象
    			return BeanUtils.instantiateClass(constructorToUse);
    		}
    		else {
    			// Must generate CGLIB subclass.
    			return instantiateWithMethodInjection(bd, beanName, owner);
    		}
    	}

**锚点三结束**  
**锚点四**

初始化属性值，对于那些@Aotuware对象就会在这一步被注入，@Values值被注入

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;
    //被注入的详细地方，如果注入的是对象，则会递归执行create(bean)方法，主要解决@Aotuware对象
    					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) {
    //主要解决@Values 值问题		
    			applyPropertyValues(beanName, mbd, bw, pvs);
    		}
    	}

**锚点四结束**

**锚点五**

对于@Service 这样的对象创建CGLIB对象

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
    		if (System.getSecurityManager() != null) {
    			AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
    				invokeAwareMethods(beanName, bean);
    				return null;
    			}, getAccessControlContext());
    		}
    		else {
    			invokeAwareMethods(beanName, bean);
    		}
    
    		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()) {
    		//创建CGLIB对象(AbstractAutoProxyCreator)
    			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    		}
    
    		return wrappedBean;
    	}

protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
            if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
                return bean;
            } else if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
                return bean;
            } else if (!this.isInfrastructureClass(bean.getClass()) && !this.shouldSkip(bean.getClass(), beanName)) {
                Object[] specificInterceptors = this.getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, (TargetSource)null);
                if (specificInterceptors != DO_NOT_PROXY) {
                    this.advisedBeans.put(cacheKey, Boolean.TRUE);
    // 创建 cglib 的 proxy 对象
                    Object proxy = this.createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
                    this.proxyTypes.put(cacheKey, proxy.getClass());
                    return proxy;
                } else {
                    this.advisedBeans.put(cacheKey, Boolean.FALSE);
                    return bean;
                }
            } else {
                this.advisedBeans.put(cacheKey, Boolean.FALSE);
                return bean;
            }
        }

**锚点五结束**

**锚点二**

for (String beanName : beanNames) {
    			Object singletonInstance = getSingleton(beanName);
    			//判断改类是否实现了SmartInitializingSingleton，进行afterSingletonsInstantiated方法执行
    			if (singletonInstance instanceof SmartInitializingSingleton) {
    				final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
    				if (System.getSecurityManager() != null) {
    					AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
    						smartSingleton.afterSingletonsInstantiated();
    						return null;
    					}, getAccessControlContext());
    				}
    				else {
    					smartSingleton.afterSingletonsInstantiated();
    				}
    			}
    		}

[Link 1]: https://blog.csdn.net/xuxie13/article/details/108790635
[SpringMVC_xml]: https://blog.csdn.net/xuxie13/article/details/108617857