Spring IOC（四）doCreateBean方法源码分析 |
您所在的位置：网站首页 › spring docreatebean方法 › Spring IOC（四）doCreateBean方法源码分析 |
|
目录
第1步：createBeanInstance，得到实例BeanWrapper第1-1步：通过工厂方法实例化，先略过第1-2步：通过默认构造函数实例化第1-3步：通过有参构造函数实例化
第2步：applyMergedBeanDefinitionPostProcessors第3步：addSingletonFactory注册早期工厂第3-1步：getEarlyBeanReference第3-2步：addSingletonFactory
第4步：populateBean属性注入第4-2步：autowireByName得到依赖属性Bean第4-3步：autowireByType得到依赖属性Bean第4-4步： @Autowired注解方式的属性注入（InstantiationAwareBeanPostProcessor），见下篇分析
第5步：initializeBean初始化第5-1步：invokeAwareMethods第5-2步：applyBeanPostProcessorsBeforeInitialization第5-3步：invokeInitMethods初始化方法（InitializingBean实现类或自定义init-method）第5-4步：applyBeanPostProcessorsAfterInitialization
第6步：依赖检查附1：自动装配附2：SmartInstantiationAwareBeanPostProcessor附3：MergedBeanDefinitionPostProcessor
真正创建Bean的过程可以概括为：
首先实例化初始Bean，注册早期工厂；
然后注入属性：调用getBean先创建它依赖的Bean；
最后进行初始化：处理aware信息的获取、BeanPostProcessor、InitializingBean等类型Bean的回调方法。
以BeanFactory的doCreateBean方法为入口，整理Bean的创建流程。 /** * Actually create the specified bean. Pre-creation processing has already happened * at this point, e.g. checking {@code postProcessBeforeInstantiation} callbacks. *Differentiates between default bean instantiation, use of a * factory method, and autowiring a constructor. * @param beanName the name of the bean * @param mbd the merged bean definition for the bean * @param args explicit arguments to use for constructor or factory method invocation * @return a new instance of the bean * @throws BeanCreationException if the bean could not be created * @see #instantiateBean * @see #instantiateUsingFactoryMethod * @see #autowireConstructor */ protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) { // Instantiate the bean. BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { instanceWrapper = createBeanInstance(beanName, mbd, args); } final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null); Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null); // Allow post-processors to modify the merged bean definition. synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); 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.isDebugEnabled()) { logger.debug("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } addSingletonFactory(beanName, new ObjectFactory() { @Override public Object getObject() throws BeansException { return getEarlyBeanReference(beanName, mbd, bean); } }); } // Initialize the bean instance. Object exposedObject = bean; try { populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { 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 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 " + "'getBeanNamesOfType' 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; } 此方法的大概功能： createBeanInstance，（默认bean实例化、工厂方法、构造函数自动装配）得到包装实例BeanWrapperapplyMergedBeanDefinitionPostProcessors，合并后的bean定义进行后期处理addSingletonFactory，提前暴露早期工厂populateBean，依赖属性装配initializeBean，调用初始化方法getSingleton，如果允许提前曝光，则检查循环依赖registerDisposableBeanIfNecessary 第1步：createBeanInstance，得到实例BeanWrapper protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) { // Make sure bean class is actually resolved at this point. Class beanClass = resolveBeanClass(mbd, beanName); if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Bean class isn't public, and non-public access not allowed: " + beanClass.getName()); } 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) { synchronized (mbd.constructorArgumentLock) { if (mbd.resolvedConstructorOrFactoryMethod != null) { resolved = true; autowireNecessary = mbd.constructorArgumentsResolved; } } } if (resolved) { if (autowireNecessary) { return autowireConstructor(beanName, mbd, null, null); } else { return instantiateBean(beanName, mbd); } } // 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); }这个方法将实例化Bean的形式分为三类： 通过工厂方法通过默认构造函数通过自动装配（构造函数形式的自动装配） 第1-1步：通过工厂方法实例化，先略过 第1-2步：通过默认构造函数实例化 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() { @Override public Object run() { return getInstantiationStrategy().instantiate(mbd, beanName, parent); } }, getAccessControlContext()); } else { 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); } }其中有一个getInstantiationStrategy()，获取BeanFactory的实例化策略实现类。有关这个策略，InstantiationStrategy是根接口，实现类有两个：SimpleInstantiationStrategy、CglibSubclassingInstantiationStrategy。其中CglibSubclassingInstantiationStrategy又继承了SimpleInstantiationStrategy。 @Override public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) { // Don't override the class with CGLIB if no overrides. if (bd.getMethodOverrides().isEmpty()) { 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(new PrivilegedExceptionAction() { @Override public Constructor run() throws Exception { return clazz.getDeclaredConstructor((Class[]) null); } }); } else { constructorToUse = clazz.getDeclaredConstructor((Class[]) null); } bd.resolvedConstructorOrFactoryMethod = constructorToUse; } catch (Exception ex) { throw new BeanInstantiationException(clazz, "No default constructor found", ex); } } } return BeanUtils.instantiateClass(constructorToUse); } else { // Must generate CGLIB subclass. return instantiateWithMethodInjection(bd, beanName, owner); } }方法首先判断了是否有MethodOverride值，也就是我们上文所说的 Spring（三）createBean方法源码分析lookup-method、replace-method属性。 如果没有MethodOverride， 通过反射创建实例 Constructor.newInstance()。如果有MethodOverride，则只能使用CglibSubclassingInstantiationStrategy策略的实例化逻辑，通过CGLib创建一个ASM增强的子类，来实现方法逻辑的代理。 第1-3步：通过有参构造函数实例化有关自动装配见附1。 首先需要确定一个构造器： // 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); }determineConstructorsFromBeanPostProcessors方法： protected Constructor[] determineConstructorsFromBeanPostProcessors(Class beanClass, String beanName) throws BeansException { if (beanClass != null && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof SmartInstantiationAwareBeanPostProcessor) { SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp; Constructor[] ctors = ibp.determineCandidateConstructors(beanClass, beanName); if (ctors != null) { return ctors; } } } } return null; }得到BeanFactory中所有的SmartInstantiationAwareBeanPostProcessor，遍历调用其determineCandidateConstructors方法。 有关SmartInstantiationAwareBeanPostProcessor详细解释见附2。 第2步：applyMergedBeanDefinitionPostProcessors protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class beanType, String beanName) throws BeansException { try { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof MergedBeanDefinitionPostProcessor) { MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp; bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName); } } } catch (Exception ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Post-processing failed of bean type [" + beanType + "] failed", ex); } }这个方法中，获取全部的MergedBeanDefinitionPostProcessor，然后遍历执行其postProcessMergedBeanDefinition方法。 有关MergedBeanDefinitionPostProcessor详细解释见附3。 第3步：addSingletonFactory注册早期工厂 if (earlySingletonExposure) { if (logger.isDebugEnabled()) { logger.debug("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } addSingletonFactory(beanName, new ObjectFactory() { @Override public Object getObject() throws BeansException { return getEarlyBeanReference(beanName, mbd, bean); } }); }这个方法中： 为此Bean创建提前暴露的工厂，工厂返回值为getEarlyBeanReferenceaddSingletonFactory，注册此工厂，处理循环依赖提前曝光 第3-1步：getEarlyBeanReference protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) { Object exposedObject = bean; if (bean != null && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof SmartInstantiationAwareBeanPostProcessor) { SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp; exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName); if (exposedObject == null) { return exposedObject; } } } } return exposedObject; }这个方法中，调用SmartInstantiationAwareBeanPostProcessor.getEarlyBeanReference方法。 在getEarlyBeanReference接口的实现过程中，有一个步骤 protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) { if (beanName != null && this.targetSourcedBeans.contains(beanName)) { return bean; } if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) { return bean; } if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) { this.advisedBeans.put(cacheKey, Boolean.FALSE); return bean; } // Create proxy if we have advice. Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null); if (specificInterceptors != DO_NOT_PROXY) { this.advisedBeans.put(cacheKey, Boolean.TRUE); Object proxy = createProxy( bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean)); this.proxyTypes.put(cacheKey, proxy.getClass()); return proxy; } this.advisedBeans.put(cacheKey, Boolean.FALSE); return bean; }可以看到，如果存在切面，则创建一个代理，spring的 AOP是基于getEarlyBeanReference 实现的，之后详细分析。 第3-2步：addSingletonFactory protected void addSingletonFactory(String beanName, ObjectFactory singletonFactory) { Assert.notNull(singletonFactory, "Singleton factory must not be null"); synchronized (this.singletonObjects) { if (!this.singletonObjects.containsKey(beanName)) { this.singletonFactories.put(beanName, singletonFactory); this.earlySingletonObjects.remove(beanName); this.registeredSingletons.add(beanName); } } }在这一步中，如果一级缓存中不存在此Bean，则从二级缓存中移除，将早期工厂加入三级缓存。 在Spring（二）doGetBean方法源码分析中的第1步：尝试从缓存中获取Bean，如果一级缓存中不存在，就会从singletonFactories中获取，此时获取的是一个早期Bean。 第4步：populateBean属性注入 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. 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. boolean continueWithPropertyPopulation = true; if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { continueWithPropertyPopulation = false; break; } } } } if (!continueWithPropertyPopulation) { return; } if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { MutablePropertyValues newPvs = new MutablePropertyValues(pvs); // Add property values based on autowire by name if applicable. if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } // Add property values based on autowire by type if applicable. if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; } boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.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); } } applyPropertyValues(beanName, mbd, bw, pvs); }在此方法中，功能大概为： 调用InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation，检查是否允许继续属性注入，如果返回值是false，则不继续属性注入，直接返回byName类型的自动装配（依赖Bean名、依赖Bean）byType类型的自动装配（依赖Bean名、依赖Bean）@Autowired注解方式的属性注入：调用InstantiationAwareBeanPostProcessor.postProcessPropertyValuescheckDependencies检查依赖，即配置文件中的dependency-check属性applyPropertyValues，将MutablePropertyValues应用到此BeanWrapper 第4-2步：autowireByName得到依赖属性Bean protected void autowireByName( String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { if (containsBean(propertyName)) { Object bean = getBean(propertyName); pvs.add(propertyName, bean); registerDependentBean(propertyName, beanName); if (logger.isDebugEnabled()) { logger.debug("Added autowiring by name from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + propertyName + "'"); } } else { if (logger.isTraceEnabled()) { logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName + "' by name: no matching bean found"); } } } }根据名字自动装配： 首先得到 所有需要装配的非简单属性 ，（不是字符串等简单类型）也就是Bean类型的属性，并返回然后 循环调用getBean(propertyName) ，也就是依次创建它依赖的Bean记录依赖关系 第4-3步：autowireByType得到依赖属性Bean protected void autowireByType( String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } Set autowiredBeanNames = new LinkedHashSet(4); String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { try { PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName); // Don't try autowiring by type for type Object: never makes sense, // even if it technically is a unsatisfied, non-simple property. if (Object.class != pd.getPropertyType()) { MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd); // Do not allow eager init for type matching in case of a prioritized post-processor. boolean eager = !PriorityOrdered.class.isAssignableFrom(bw.getWrappedClass()); DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager); Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter); if (autowiredArgument != null) { pvs.add(propertyName, autowiredArgument); } for (String autowiredBeanName : autowiredBeanNames) { registerDependentBean(autowiredBeanName, beanName); if (logger.isDebugEnabled()) { logger.debug("Autowiring by type from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + autowiredBeanName + "'"); } } autowiredBeanNames.clear(); } } catch (BeansException ex) { throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex); } } }根据类型自动装配： 首先得到 所有需要装配的非简单属性 ，（不是字符串等简单类型）也就是Bean类型的属性，并返回检查此属性的set方法，存在的时候才可自动装配resolveDependency， 通过Type解析依赖关系，返回依赖的Bean实例 （找到所有类型为此Type的Bean，如果个数不为1，则抛出错误），具体的方法分析见下篇。记录依赖关系 第4-4步： @Autowired注解方式的属性注入（InstantiationAwareBeanPostProcessor），见下篇分析 第5步：initializeBean初始化 protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { if (System.getSecurityManager() != null) { AccessController.doPrivileged(new PrivilegedAction() { @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; }此方法包括的操作有： invokeAwareMethodsapplyBeanPostProcessorsBeforeInitializationinvokeInitMethodsapplyBeanPostProcessorsAfterInitialization 第5-1步：invokeAwareMethods 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); } } }这一步的目的是让开发者得到BeanFactory中的一些属性：BeanName、BeanClassLoader、BeanFactory spring Aware是什么？ spring IOC的特点是开发者对于spring容器是无感知的，而aware的意义却是"有感知"的。当我们在项目中需要用到spring容器本身的一些资源时，就需要用到spring提供的Aware接口。实现类有以下几个：BeanNameAware：获取容器中 Bean 的名称；BeanFactoryAware：获取当前 BeanFactory；ApplicationContextAware：获取当前ApplicationContext；MessageSourceAware：获取 Message Source 相关文本信息；ApplicationEventPublisherAware：发布事件；ResourceLoaderAware：获取资源加载器，获取外部资源文件。 第5-2步：applyBeanPostProcessorsBeforeInitialization public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName) throws BeansException { Object result = existingBean; for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) { result = beanProcessor.postProcessBeforeInitialization(result, beanName); if (result == null) { return result; } } return result; }在此方法中获取全部的BeanPostProcessor，然后遍历执行其postProcessBeforeInitialization方法。 第5-3步：invokeInitMethods初始化方法（InitializingBean实现类或自定义init-method） protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd) throws Throwable { 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() { @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) { String initMethodName = mbd.getInitMethodName(); if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) && !mbd.isExternallyManagedInitMethod(initMethodName)) { invokeCustomInitMethod(beanName, bean, mbd); } } }在方法中 首先找到InitializingBean类型的Bean，调用其afterPropertiesSet方法通过反射调用自定义的Init-Method 第5-4步：applyBeanPostProcessorsAfterInitialization 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; }在此方法中获取全部的BeanPostProcessor，然后遍历执行其postProcessAfterInitialization方法。 第6步：依赖检查这一步没看懂。。 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 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 " + "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example."); } } } } 附1：自动装配自动装配的意义在于，在xml中声明Bean之间的依赖关系； spring提供了4种自动装配的形式： NO：必须使用"ref"来声明依赖关系 public class Animal { private Cat cat; public Cat getCat() { return this.cat; } public void setCat(Cat cat) { this.cat = cat; } } public class Cat { public String toString() { return "miao"; } } ByName：把与Bean的属性具有 相同名字 的其他Bean自动装配到Bean的对应属性中 ByType：把与Bean的属性具有 相同类型 的其他Bean自动装配到Bean的对应属性中 Constructor：把与Bean的 构造器入参 具有 相同类型 的其他Bean自动装配到Bean构造器的对应入参中 public class Animal { private Cat cat; public Animal(Cat cat) { this.cat = cat; } public Cat getCat() { return this.cat; } public void setCat(Cat cat) { this.cat = cat; } }注意byName和byType的类型，都是使用默认构造器创建实例，然后使用setter进行属性的注入；而constructor是直接根据带参数的构造函数创建实例。本章中的第1-3步是指constructor类型。 默认情况下，default-autowire属性被设置为none，表示所有的Bean都不使用自动装配。 现在我们在工程中很少使用上述方法，而是使用@Autowired注解的方式。 附2：SmartInstantiationAwareBeanPostProcessor该接口继承自InstantiationAwareBeanPostProcessor，除了继承的5个方法外，自己扩展了三个方法： public interface SmartInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessor { Class predictBeanType(Class beanClass, String beanName) throws BeansException; Constructor[] determineCandidateConstructors(Class beanClass, String beanName) throws BeansException; Object getEarlyBeanReference(Object bean, String beanName) throws BeansException; }这是一个专用的接口，一般在框架内使用。通常应用程序提供的后处理器应该简单地实现普通的BeanPostProcessor接口，或者从InstantiationAwareBeanPostProcessorAdapter类派生。 predictBeanType 预测bean的类型，在beanFactory的getType时被调用。determineCandidateConstructors 该方法可以返回要用于beanClass的候选构造函数getEarlyBeanReference 获取对指定bean的早期访问的引用，通常用于解析循环引用。 附3：MergedBeanDefinitionPostProcessor该接口继承自BeanPostProcessor，除了继承的3个方法外，自己扩展了一个方法： public interface MergedBeanDefinitionPostProcessor extends BeanPostProcessor { void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class beanType, String beanName); }此方法对MergedBeanDefinition进行修改，即对合并后的 bean定义 进行后期处理，@Autowired通过此方法实现注入类型的预解析。 |
今日新闻 |
推荐新闻 |
| CopyRight 2018-2019 办公设备维修网 版权所有 豫ICP备15022753号-3 |