spring源码分析(四)-创建bean的源码分析

Love The Way You Lie 2022-12-28 11:10 235阅读 0赞

### 文章目录 ###

*   *   *  createBean方法
         *  doCreateBean
         *   *  createBeanInstance创建bean实例
             *   *  就看一下简单通过构造函数进行bean初始化instantiateBean方法
                 *  instantiate方法获取对应的策略去执行初始化方法
                 *   *  BeanUtils.instantiateClass的方法就是通过Constructor构造实例
             *  doCreateBean方法里面还有比较重要的方法populateBean
             *   *  applyPropertyValues,真正进行属性赋值的地方
             *  doCreateBean方法里面还有比较重要的方法initializeBean
             *   *  invokeAwareMethods 执行三个aware接口方法
                 *  applyBeanPostProcessorsBeforeInitialization,执行bean后置处理器的postProcessBeforeInitialization方法
                 *  invokeInitMethods init方法afterPropertiesSet方法

### createBean方法 ###

@Override
    	protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException { 
    		if (logger.isDebugEnabled()) { 
    			logger.debug("Creating instance of bean '" + beanName + "'");
    		}
    		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.
    		// 解析beanName对应的Bean的类型,例如 org.springframework.beans.factory.config.BeanPostProcessor
    		Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
    		//如果resolvedClass存在,并且mbd的beanClass类型不是Class,并且mbd的beanClass不为空(代表beanClass存的是class的name)
    		if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { 
    			//是用mbd深拷贝一个新的RootBeanDefinition的副本;
    			mbdToUse = new RootBeanDefinition(mbd);
    			// 并且将解析的resolvedClass赋值给拷贝的对象,使用拷贝的副本用于后续操作
    			mbdToUse.setBeanClass(resolvedClass);
    		}
    
    		// Prepare method overrides.
    		try { 
    			// 验证准备覆盖的方法(对override属性进行标记验证)
    			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.
    // 实例化前处理,给InstantiationAwareBeanPostProcessors一个机会返回代理对象来代替真正的bean实例
    			Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
    			//如果bean不为空跳过spring默认的实例化过程,直接返回bean
    			if (bean != null) { 
    				return bean;
    			}
    		}
    		catch (Throwable ex) { 
    			throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
    					"BeanPostProcessor before instantiation of bean failed", ex);
    		}
    		// 真正创建bean的方法
    		Object beanInstance = doCreateBean(beanName, mbdToUse, args);
    		if (logger.isDebugEnabled()) { 
    			logger.debug("Finished creating instance of bean '" + beanName + "'");
    		}
    		return beanInstance;
    	}

### doCreateBean ###

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
    			throws BeanCreationException { 
    
    		// Instantiate the bean.
    		// 新建bean的包装类
    		BeanWrapper instanceWrapper = null;
    		if (mbd.isSingleton()) { 
    			// 如果是工厂bean,需要先移除未完成的factoryBean实例的缓存
    			instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
    		}
    		if (instanceWrapper == null) { 
    			// 根据beanName,mbd,args使用对应的策略创建bean实例,并返回包装类BeanWrapper
    			instanceWrapper = createBeanInstance(beanName, mbd, args);
    		}
    		// 拿到创建好的Bean实例
    		final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
    		// 拿到bean实例的类型
    		Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
    		mbd.resolvedTargetType = beanType;
    
    		// Allow post-processors to modify the merged bean definition.
    		// 允许后置处理器修改合并的bean定义
    		synchronized (mbd.postProcessingLock) { 
    			if (!mbd.postProcessed) { 
    				try { 
    					// 应用后置处理器MergedBeanDefinitionPostProcessor,允许修改MergedBeanDefinitio
    					//@Autowired注解正是通过这个方法实现注入类型的预解析
    					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.
    		// 判断是否需要提前曝光实例,是否是单例,循环依赖,是否正在创建
    		boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
    				isSingletonCurrentlyInCreation(beanName));
    		if (earlySingletonExposure) { 
    			if (logger.isDebugEnabled()) { 
    				logger.debug("Eagerly caching bean '" + beanName +
    						"' to allow for resolving potential circular references");
    			}
    			// 提前曝光beanName的ObjectFactory用于解决循环依赖
    			addSingletonFactory(beanName, new ObjectFactory<Object>() { 
    				@Override
    				public Object getObject() throws BeansException { 
    					// 应用后置处理器SmartInstantiationAwareBeanPostProcessor
    					// 允许返回指定bean的早期引用，若没有则直接返回bean
    					return getEarlyBeanReference(beanName, mbd, bean);
    				}
    			});
    		}
    
    		// Initialize the bean instance.
    		//初始化bean
    		Object exposedObject = bean;
    		try { 
    			//对bean进行属性填充,存在循环依赖,依赖其他bean的属性,会递归初始化依赖bean实例
    			populateBean(beanName, mbd, instanceWrapper);
    			if (exposedObject != null) { 
    				// 初始化bean,执行BeanPostProcessor的postProcessBeforeInitialization方法
    				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) { 
    			// 如果允许提前曝光实例,则进行循环依赖检查
    			Object earlySingletonReference = getSingleton(beanName, false);
    			// earlySingletonReference只有在当前解析的bean存在循环依赖的情况下才会不为空
    			if (earlySingletonReference != null) { 
    				if (exposedObject == bean) { 
    					// 如果exposedObject没有在initializeBean方法中被增强，则不影响之前的循环引用
    					exposedObject = earlySingletonReference;
    				}
    				else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { 
    					// 如果exposedObject在initializeBean方法中被增强 && 不允许在循环引用的情况下使用注入原始bean实例
    					// && 当前bean有被其他bean依赖
    
    					//拿到当前bean的所有依赖bean的名称的数组
    					String[] dependentBeans = getDependentBeans(beanName);
    					Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
    					for (String dependentBean : dependentBeans) { 
    						// 尝试移除这些bean实例,因为这些bean依赖的bean已经被增强了,
    						if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { 
    							// 移除失败的加到actualDependentBeans
    							actualDependentBeans.add(dependentBean);
    						}
    					}
    					// 如果存在移除失败的，则抛出异常，因为存在bean依赖了“脏数据”
    					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 { 
    			// 注册用于销毁的bean,执行销毁操作的有三种：自定义destroy方法、DisposableBean接口、DestructionAwareBeanPostProcessor
    			registerDisposableBeanIfNecessary(beanName, bean, mbd);
    		}
    		catch (BeanDefinitionValidationException ex) { 
    			throw new BeanCreationException(
    					mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
    		}
    
    		return exposedObject;
    	}

#### createBeanInstance创建bean实例 ####

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) { 
    		// Make sure bean class is actually resolved at this point.
    		// 解析bean类型信息
    		Class<?> beanClass = resolveBeanClass(mbd, beanName);
    
    		if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) { 
    			// beanClass不为空 && beanClass不是公开类（不是public修饰） && 该bean不允许访问非公共构造函数和方法，则抛异常
    			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
    					"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
    		}
    
    		// 如果存在工厂方法则使用工厂方法创建bean
    		if (mbd.getFactoryMethodName() != null) { 
    			return instantiateUsingFactoryMethod(beanName, mbd, args);
    		}
    
    		// Shortcut when re-creating the same bean...
    		boolean resolved = false;
    		boolean autowireNecessary = false;
    		if (args == null) { 
    			// 锁
    			synchronized (mbd.constructorArgumentLock) { 
    				if (mbd.resolvedConstructorOrFactoryMethod != null) { 
    					// 如果resolvedConstructorOrFactoryMethod缓存不为空,则将resolved标记为已解析
    					resolved = true;
    					// 根据constructorArgumentsResolved判断是否需要自动注入
    					autowireNecessary = mbd.constructorArgumentsResolved;
    				}
    			}
    		}
    		if (resolved) { 
    			// 如果已经解析过,则使用resolvedConstructorOrFactoryMethod缓存里解析好的构造函数方法
    			if (autowireNecessary) { 
    				// 需要自动注入，则执行构造函数自动注入
    				return autowireConstructor(beanName, mbd, null, null);
    			}
    			else { 
    				// 使用默认的构造函数进行bean的实例化
    				return instantiateBean(beanName, mbd);
    			}
    		}
    
    		// Candidate constructors for autowiring?
    		// 应用后置处理器SmartInstantiationAwareBeanPostProcessor，拿到bean的候选构造函数
    		Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
    		if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||
    				mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) { 
    			// 如果ctors不为空 || mbd的注入方式为AUTOWIRE_CONSTRUCTOR || mdb定义了构造函数的参数值 || args不为空，则执行构造函数自动注入
    			return autowireConstructor(beanName, mbd, ctors, args);
    		}
    
    		// No special handling: simply use no-arg constructor.
    		// 没有特殊处理,使用默认的构造函数进行bean初始化
    		return instantiateBean(beanName, mbd);
    	}

##### 就看一下简单通过构造函数进行bean初始化instantiateBean方法 #####

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) { 
    		try { 
    			Object beanInstance;
    			final BeanFactory parent = this;
    			if (System.getSecurityManager() != null) { 
    				beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() { 
    					@Override
    					public Object run() { 
    						return getInstantiationStrategy().instantiate(mbd, beanName, parent);
    					}
    				}, getAccessControlContext());
    			}
    			else { 
    				// 获取创建bean实例的策略,调用策略的instantiate方法进行实例化
    				// 默认实例化cglib private InstantiationStrategy instantiationStrategy = new CglibSubclassingInstantiationStrategy();
    				beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
    			}
    			//把实例包装成BeanWrapper并且初始化一下beanWrapper的值
    			BeanWrapper bw = new BeanWrapperImpl(beanInstance);
    			initBeanWrapper(bw);
    			return bw;
    		}
    		catch (Throwable ex) { 
    			throw new BeanCreationException(
    					mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
    		}
    	}

##### instantiate方法获取对应的策略去执行初始化方法 #####

@Override
    	public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) { 
    		// Don't override the class with CGLIB if no overrides.
    		// 如果MethOverrides为空
    		if (bd.getMethodOverrides().isEmpty()) { 
    			Constructor<?> constructorToUse;
    			synchronized (bd.constructorArgumentLock) { 
    				// 获取bd.resolvedConstructorOrFactoryMethod已解析的构造器或工厂方法
    				constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
    				//如果为空
    				if (constructorToUse == null) { 
    					final Class<?> clazz = bd.getBeanClass();
    					// 如果是接口,抛出异常
    					if (clazz.isInterface()) { 
    						throw new BeanInstantiationException(clazz, "Specified class is an interface");
    					}
    					try { 
    						if (System.getSecurityManager() != null) { 
    							constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor<?>>() { 
    								@Override
    								public Constructor<?> run() throws Exception { 
    									return clazz.getDeclaredConstructor((Class[]) null);
    								}
    							});
    						}
    						else { 
    							//通过bean的类clazz来得到声明的构造函数
    							constructorToUse =	clazz.getDeclaredConstructor((Class[]) null);
    						}
    						// 并赋值回给bd.resolvedConstructorOrFactoryMethod
    						bd.resolvedConstructorOrFactoryMethod = constructorToUse;
    					}
    					catch (Throwable ex) { 
    						throw new BeanInstantiationException(clazz, "No default constructor found", ex);
    					}
    				}
    			}
    			// 通过BeanUtils方法实例化bean
    			return BeanUtils.instantiateClass(constructorToUse);
    		}
    		else { 
    			// Must generate CGLIB subclass.
    			// 如果MethodOverrides不为空,生成cglib的子类
    			return instantiateWithMethodInjection(bd, beanName, owner);
    		}
    	}

###### BeanUtils.instantiateClass的方法就是通过Constructor构造实例 ######

public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException { 
    		Assert.notNull(ctor, "Constructor must not be null");
    		try { 
    			ReflectionUtils.makeAccessible(ctor);
    			return ctor.newInstance(args);
    		}
    		catch (InstantiationException ex) { 
    			throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);
    		}
    		catch (IllegalAccessException ex) { 
    			throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);
    		}
    		catch (IllegalArgumentException ex) { 
    			throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);
    		}
    		catch (InvocationTargetException ex) { 
    			throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());
    		}
    	}

这时候最初始的bean就被实例化了~

#### doCreateBean方法里面还有比较重要的方法populateBean ####

populateBean方法就是对bean属性进行赋值;  
源码:

ByName(beanName, mbd, bw, newPvs);
    			}
    			// Add property values based on autowire by type if applicable.
    			// 根据类型注入
    			if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) { 
    				autowireByType(beanName, mbd, bw, newPvs);
    			}
    			//对变量的重新定义
    			pvs = newPvs;
    		}
    
    		boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
    		boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
    
    		if (hasInstAwareBpps || needsDepCheck) { 
    			PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
    			if (hasInstAwareBpps) { 
    				// 执行InstantiationAwareBeanPostProcessor的postProcessPropertyValues方法
    				for (BeanPostProcessor bp : getBeanPostProcessors()) { 
    					if (bp instanceof InstantiationAwareBeanPostProcessor) { 
    						InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
    						pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
    						if (pvs == null) { 
    							return;
    						}
    					}
    				}
    			}
    			//对dependency-check属性的支持，默认是不校验
    			if (needsDepCheck) { 
    				checkDependencies(beanName, mbd, filteredPds, pvs);
    			}
    		}
    		//对属性进行注入
    		applyPropertyValues(beanName, mbd, bw, pvs);
    	}

##### applyPropertyValues,真正进行属性赋值的地方 #####

protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) { 
    		if (pvs == null || pvs.isEmpty()) { 
    			return;
    		}
    
    		if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) { 
    			((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
    		}
    
    		MutablePropertyValues mpvs = null;
    		List<PropertyValue> original;
    
    		if (pvs instanceof MutablePropertyValues) { 
    			// 如果mpvs中的值已经被转换为对应的类型，那么可以直接设置到beanWrapper中
    			mpvs = (MutablePropertyValues) pvs;
    			if (mpvs.isConverted()) { 
    				// Shortcut: use the pre-converted values as-is.
    				try { 
    					bw.setPropertyValues(mpvs);
    					return;
    				}
    				catch (BeansException ex) { 
    					throw new BeanCreationException(
    							mbd.getResourceDescription(), beanName, "Error setting property values", ex);
    				}
    			}
    			original = mpvs.getPropertyValueList();
    		}
    		else { 
    			// 如果pvs并不是使用MutablePropertyValues封装的类型，那么直接使用原始的属性获取方法
    			original = Arrays.asList(pvs.getPropertyValues());
    		}
    
    		TypeConverter converter = getCustomTypeConverter();
    		if (converter == null) { 
    			converter = bw;
    		}
    		// 获取对应的解析器
    		BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
    
    		// Create a deep copy, resolving any references for values.
    		List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size());
    		boolean resolveNecessary = false;
    		// 遍历属性,将属性转换为对应类的属性类型
    		for (PropertyValue pv : original) { 
    			if (pv.isConverted()) { 
    				deepCopy.add(pv);
    			}
    			else { 
    				String propertyName = pv.getName();
    				Object originalValue = pv.getValue();
    				Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
    				Object convertedValue = resolvedValue;
    				boolean convertible = bw.isWritableProperty(propertyName) &&
    						!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
    				if (convertible) { 
    					convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
    				}
    				// Possibly store converted value in merged bean definition,
    				// in order to avoid re-conversion for every created bean instance.
    				if (resolvedValue == originalValue) { 
    					if (convertible) { 
    						pv.setConvertedValue(convertedValue);
    					}
    					deepCopy.add(pv);
    				}
    				else if (convertible && originalValue instanceof TypedStringValue &&
    						!((TypedStringValue) originalValue).isDynamic() &&
    						!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) { 
    					pv.setConvertedValue(convertedValue);
    					deepCopy.add(pv);
    				}
    				else { 
    					resolveNecessary = true;
    					deepCopy.add(new PropertyValue(pv, convertedValue));
    				}
    			}
    		}
    		if (mpvs != null && !resolveNecessary) { 
    			mpvs.setConverted();
    		}
    
    		// Set our (possibly massaged) deep copy.
    		try { 
    			//通过反射将属性赋值,就不细看了,太复杂
    			bw.setPropertyValues(new MutablePropertyValues(deepCopy));
    		}
    		catch (BeansException ex) { 
    			throw new BeanCreationException(
    					mbd.getResourceDescription(), beanName, "Error setting property values", ex);
    		}
    	}

//通过反射将属性赋值,就不细看了,太复杂  
bw.setPropertyValues(new MutablePropertyValues(deepCopy));  
最后一步通过BeanWrapper封装的方法进行属性赋值,也是通过反射,感兴趣的可以点进去看看~

#### doCreateBean方法里面还有比较重要的方法initializeBean ####

源码:

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { 
    		if (System.getSecurityManager() != null) { 
    			AccessController.doPrivileged(new PrivilegedAction<Object>() { 
    				@Override
    				public Object run() { 
    					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()) { 
    			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    		}
    		return wrappedBean;
    	}

> initializeBean方法主要执行了一些aware接口(BeanNameAware,BeanFactoryAware);执行bean后置处理器的postProcessBeforeInitialization方法,然后就是实现了InitializingBean接口的afterPropertiesSet方法和配置的init方法了

##### invokeAwareMethods 执行三个aware接口方法 #####

private void invokeAwareMethods(final String beanName, final Object bean) { 
    		if (bean instanceof Aware) { 
    			if (bean instanceof BeanNameAware) { 
    				((BeanNameAware) bean).setBeanName(beanName);
    			}
    			if (bean instanceof BeanClassLoaderAware) { 
    				((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
    			}
    			if (bean instanceof BeanFactoryAware) { 
    				((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
    			}
    		}
    	}

##### applyBeanPostProcessorsBeforeInitialization,执行bean后置处理器的postProcessBeforeInitialization方法 #####

@Override
    	public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
    			throws BeansException { 
    
    		Object result = existingBean;
    		for (BeanPostProcessor processor : getBeanPostProcessors()) { 
    			result = processor.postProcessBeforeInitialization(result, beanName);
    			if (result == null) { 
    				return result;
    			}
    		}
    		return result;
    	}

##### invokeInitMethods init方法afterPropertiesSet方法 #####

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
    			throws Throwable { 
    //判断接口是否实现了InitializingBean接口
    		boolean isInitializingBean = (bean instanceof InitializingBean);
    		if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) { 
    			if (logger.isDebugEnabled()) { 
    				logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
    			}
    			if (System.getSecurityManager() != null) { 
    				try { 
    					AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() { 
    						@Override
    						public Object run() throws Exception { 
    							((InitializingBean) bean).afterPropertiesSet();
    							return null;
    						}
    					}, getAccessControlContext());
    				}
    				catch (PrivilegedActionException pae) { 
    					throw pae.getException();
    				}
    			}
    			else { 
    				((InitializingBean) bean).afterPropertiesSet();
    			}
    		}
    
    		if (mbd != null) { 
    			//判断是否设置了init 方法
    			String initMethodName = mbd.getInitMethodName();
    			if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
    					!mbd.isExternallyManagedInitMethod(initMethodName)) { 
    				//通过反射执行设置的init方法
    				invokeCustomInitMethod(beanName, bean, mbd);
    			}
    		}
    	}