Bean 容器实例化完成后 接着上一篇我们回到 refresh()
方法,我重新贴了一遍代码,看看我们说到哪了。上篇说完 obtainFreshBeanFactory()
方法。
考虑到篇幅,这里开始大幅缩减掉没必要详细介绍的部分,大家直接看下面的代码中的注释就好了。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 @Override public void refresh () throws BeansException, IllegalStateException { synchronized (this .startupShutdownMonitor) { prepareRefresh(); ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); prepareBeanFactory(beanFactory); try { postProcessBeanFactory(beanFactory); invokeBeanFactoryPostProcessors(beanFactory); registerBeanPostProcessors(beanFactory); initMessageSource(); initApplicationEventMulticaster(); onRefresh(); registerListeners(); finishBeanFactoryInitialization(beanFactory); finishRefresh(); } catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } destroyBeans(); cancelRefresh(ex); throw ex; } finally { resetCommonCaches(); } } }
准备 Bean 容器: prepareBeanFactory 之前我们说过,Spring
把我们在 xml
配置的 bean
都注册以后,会”手动”注册一些特殊的 bean
。
这里简单介绍下 prepareBeanFactory(factory) 方法:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 protected void prepareBeanFactory (ConfigurableListableBeanFactory beanFactory) { beanFactory.setBeanClassLoader(getClassLoader()); beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader())); beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this , getEnvironment())); beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this )); beanFactory.ignoreDependencyInterface(EnvironmentAware.class); beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class); beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class); beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class); beanFactory.ignoreDependencyInterface(MessageSourceAware.class); beanFactory.ignoreDependencyInterface(ApplicationContextAware.class); beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory); beanFactory.registerResolvableDependency(ResourceLoader.class, this ); beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this ); beanFactory.registerResolvableDependency(ApplicationContext.class, this ); beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this )); if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); } if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) { beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment()); } if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) { beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties()); } if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) { beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment()); } }
在上面这块代码中,Spring
对一些特殊的 bean
进行了处理,读者如果暂时还不能消化它们也没有关系,慢慢往下看。
初始化所有的 singleton beans 我们的重点当然是 finishBeanFactoryInitialization(beanFactory); 这个巨头了,这里会负责初始化所有的 singleton beans
。
注意,后面的描述中,我都会使用初始化或预初始化来代表这个阶段,Spring 会在这个阶段完成所有的 singleton beans
的实例化。
我们来总结一下,到目前为止,应该说 BeanFactory
已经创建完成,并且所有的实现了 BeanFactoryPostProcessor
接口的 Bean
都已经初始化并且其中的 postProcessBeanFactory(factory)
方法已经得到回调执行了。而且 Spring
已经“手动”注册了一些特殊的 Bean
,如 environment
、systemProperties
等。剩下的就是初始化 singleton beans
了,我们知道它们是单例的,如果没有设置懒加载,那么 Spring
会在接下来初始化所有的 singleton beans
。
// AbstractApplicationContext.java
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 protected void finishBeanFactoryInitialization (ConfigurableListableBeanFactory beanFactory) { 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)); } if (!beanFactory.hasEmbeddedValueResolver()) { beanFactory.addEmbeddedValueResolver(new StringValueResolver() { @Override public String resolveStringValue (String strVal) { return getEnvironment().resolvePlaceholders(strVal); } }); } String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false , false ); for (String weaverAwareName : weaverAwareNames) { getBean(weaverAwareName); } beanFactory.setTempClassLoader(null ); beanFactory.freezeConfiguration(); beanFactory.preInstantiateSingletons(); }
从上面最后一行往里看,我们就又回到 DefaultListableBeanFactory
这个类了,这个类大家应该都不陌生了吧。
// DefaultListableBeanFactory
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 @Override public void preInstantiateSingletons () throws BeansException { if (this .logger.isDebugEnabled()) { this .logger.debug("Pre-instantiating singletons in " + this ); } List<String> beanNames = new ArrayList<String>(this .beanDefinitionNames); for (String beanName : beanNames) { RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { if (isFactoryBean(beanName)) { final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName); boolean isEagerInit; if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) { isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() { @Override public Boolean run () { return ((SmartFactoryBean<?>) factory).isEagerInit(); } }, getAccessControlContext()); } else { isEagerInit = (factory instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factory).isEagerInit()); } if (isEagerInit) { getBean(beanName); } } else { getBean(beanName); } } } for (String beanName : beanNames) { Object singletonInstance = getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance; if (System.getSecurityManager() != null ) { AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run () { smartSingleton.afterSingletonsInstantiated(); return null ; } }, getAccessControlContext()); } else { smartSingleton.afterSingletonsInstantiated(); } } } }
接下来,我们就进入到 getBean(beanName) 方法了,这个方法我们经常用来从 BeanFactory
中获取一个 Bean
,而初始化的过程也封装到了这个方法里。
// AbstractBeanFactory
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 @Override public Object getBean (String name) throws BeansException { return doGetBean(name, null , null , false ); } @SuppressWarnings("unchecked") protected <T> T doGetBean ( final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException { final String beanName = transformedBeanName(name); Object bean; Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null ) { if (logger.isDebugEnabled()) { if (isSingletonCurrentlyInCreation(beanName)) { logger.debug("..." ); } else { logger.debug("Returning cached instance of singleton bean '" + beanName + "'" ); } } bean = getObjectForBeanInstance(sharedInstance, name, beanName, null ); } else { if (isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { String nameToLookup = originalBeanName(name); if (args != null ) { return (T) parentBeanFactory.getBean(nameToLookup, args); } else { return parentBeanFactory.getBean(nameToLookup, requiredType); } } if (!typeCheckOnly) { markBeanAsCreated(beanName); } try { final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); 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); } } if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() { @Override public Object getObject () throws BeansException { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { destroySingleton(beanName); throw ex; } } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } else if (mbd.isPrototype()) { Object prototypeInstance = null ; try { beforePrototypeCreation(beanName); prototypeInstance = createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } else { 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; } } if (requiredType != null && bean != null && !requiredType.isInstance(bean)) { try { return getTypeConverter().convertIfNecessary(bean, requiredType); } 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()); } } return (T) bean; }
大家应该也猜到了,接下来当然是分析 createBean
方法:
1 protected abstract Object createBean (String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException ;
第三个参数 args
数组代表创建实例需要的参数,不就是给构造方法用的参数,或者是工厂 Bean 的参数嘛,不过要注意,在我们的初始化阶段,args
是 null
。
这回我们要到一个新的类了 AbstractAutowireCapableBeanFactory
,看类名,AutowireCapable?类名是不是也说明了点问题了。
主要是为了以下场景,采用 @Autowired
注解注入属性值:
1 2 3 4 5 6 7 8 public class MessageServiceImpl implements MessageService { @Autowired private UserService userService; public String getMessage () { return userService.getMessage(); } }
1 <bean id ="messageService" class ="com.javadoop.example.MessageServiceImpl" />
以上这种属于混用了 xml
和 注解
两种方式的配置方式,Spring
会处理这种情况。
好了,读者要知道这么回事就可以了,继续向前。
// AbstractAutowireCapableBeanFactory
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 @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; Class<?> resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null ) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } try { mbdToUse.prepareMethodOverrides(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(), beanName, "Validation of method overrides failed" , ex); } try { 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); } Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (logger.isDebugEnabled()) { logger.debug("Finished creating instance of bean '" + beanName + "'" ); } return beanInstance; }
创建 Bean
我们继续往里看 doCreateBean
这个方法:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 protected Object doCreateBean (final String beanName, final RootBeanDefinition mbd, final Object[] args) throws BeanCreationException { 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 ); mbd.resolvedTargetType = beanType; 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 ; } } 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<Object>() { @Override public Object getObject () throws BeansException { return getEarlyBeanReference(beanName, mbd, bean); } }); } 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<String> actualDependentBeans = new LinkedHashSet<String>(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." ); } } } } try { registerDisposableBeanIfNecessary(beanName, bean, mbd); } catch (BeanDefinitionValidationException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Invalid destruction signature" , ex); } return exposedObject; }
到这里,我们已经分析完了 doCreateBean
方法,总的来说,我们已经说完了整个初始化流程。接下来我们挑 doCreateBean
中的三个细节出来说说。一个是创建 Bean 实例的 createBeanInstance
方法,一个是依赖注入的 populateBean
方法,还有就是回调方法 initializeBean
。
注意了,接下来的这三个方法要认真说那也是极其复杂的,很多地方我就点到为止了,感兴趣的读者可以自己往里看,最好就是碰到不懂的,自己写代码去调试它。
创建 Bean 实例我们先看看 createBeanInstance
方法。需要说明的是,这个方法如果每个分支都分析下去,必然也是极其复杂冗长的,我们挑重点说。此方法的目的就是实例化我们指定的类。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 protected BeanWrapper createBeanInstance (String beanName, RootBeanDefinition mbd, Object[] args) { 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); } 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); } } Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName); if (ctors != null || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR || mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) { return autowireConstructor(beanName, mbd, ctors, args); } return instantiateBean(beanName, mbd); }
挑个简单的无参构造函数构造实例来看看:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 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 { 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); } }
我们可以看到,关键的地方在于:
1 beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
这里会进行实际的实例化过程,我们进去看看:
// SimpleInstantiationStrategy
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 @Override public Object instantiate (RootBeanDefinition bd, String beanName, BeanFactory owner) { 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<Constructor<?>>() { @Override public Constructor<?> run() throws Exception { return clazz.getDeclaredConstructor((Class[]) null ); } }); } else { constructorToUse = clazz.getDeclaredConstructor((Class[]) null ); } bd.resolvedConstructorOrFactoryMethod = constructorToUse; } catch (Throwable ex) { throw new BeanInstantiationException(clazz, "No default constructor found" , ex); } } } return BeanUtils.instantiateClass(constructorToUse); } else { return instantiateWithMethodInjection(bd, beanName, owner); } }
到这里,我们就算实例化完成了。我们开始说怎么进行属性注入。
bean 属性注入
看完了 createBeanInstance(...)
方法,我们来看看 populateBean(...)
方法,该方法负责进行属性设值,处理依赖。
// AbstractAutowireCapableBeanFactory
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 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 { return ; } } 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); if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } 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); }
initializeBean
属性注入完成后,这一步其实就是处理各种回调了,这块代码比较简单。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 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; }
大家发现没有,BeanPostProcessor
的两个回调都发生在这边,只不过中间处理了 init-method
,是不是和读者原来的认知有点不一样了?