Spring源码分析非懒加载的Bean实例化过程（下篇）
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doCreateBean方法
上文【Spring源码分析】非懒加载的单例Bean初始化过程（上篇），分析了单例的Bean初始化流程，并跟踪代码进入了主流程，看到了Bean是如何被实例化出来的。先贴一下AbstractAutowireCapableBeanFactory的doCreateBean方法代码：
1 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) { 2 // Instantiate the bean. 3 BeanWrapper instanceWrapper = null; 4 if (mbd.isSingleton()) { 5 instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); 6 } 7 if (instanceWrapper == null) { 8 instanceWrapper = createBeanInstance(beanName, mbd, args); 9 } 10 final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null); 11 Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null); 12 13 // Allow post-processors to modify the merged bean definition. 14 synchronized (mbd.postProcessingLock) { 15 if (!mbd.postProcessed) { 16 applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); 17 mbd.postProcessed = true; 18 } 19 } 20 21 // Eagerly cache singletons to be able to resolve circular references 22 // even when triggered by lifecycle interfaces like BeanFactoryAware. 23 boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && 24 isSingletonCurrentlyInCreation(beanName)); 25 if (earlySingletonExposure) { 26 if (logger.isDebugEnabled()) { 27 logger.debug("Eagerly caching bean \'" + beanName + 28 "\' to allow for resolving potential circular references"); 29 } 30 addSingletonFactory(beanName, new ObjectFactory() { 31 public Object getObject() throws BeansException { 32 return getEarlyBeanReference(beanName, mbd, bean); 33 } 34 }); 35 } 36 37 // Initialize the bean instance. 38 Object exposedObject = bean; 39 try { 40 populateBean(beanName, mbd, instanceWrapper); 41 if (exposedObject != null) { 42 exposedObject = initializeBean(beanName, exposedObject, mbd); 43 } 44 } 45 catch (Throwable ex) { 46 if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) { 47 throw (BeanCreationException) ex; 48 } 49 else { 50 throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex); 51 } 52 } 53 54 if (earlySingletonExposure) { 55 Object earlySingletonReference = getSingleton(beanName, false); 56 if (earlySingletonReference != null) { 57 if (exposedObject == bean) { 58 exposedObject = earlySingletonReference; 59 } 60 else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { 61 String[] dependentBeans = getDependentBeans(beanName); 62 Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length); 63 for (String dependentBean : dependentBeans) { 64 if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { 65 actualDependentBeans.add(dependentBean); 66 } 67 } 68 if (!actualDependentBeans.isEmpty()) { 69 throw new BeanCurrentlyInCreationException(beanName, 70 "Bean with name \'" + beanName + "\' has been injected into other beans [" + 71 StringUtils.collectionToCommaDelimitedString(actualDependentBeans) + 72 "] in its raw version as part of a circular reference, but has eventually been " + 73 "wrapped. This means that said other beans do not use the final version of the " + 74 "bean. This is often the result of over-eager type matching - consider using " + 75 "\'getBeanNamesOfType\' with the \'allowEagerInit\' flag turned off, for example."); 76 } 77 } 78 } 79 } 80 81 // Register bean as disposable. 82 try { 83 registerDisposableBeanIfNecessary(beanName, bean, mbd); 84 } 85 catch (BeanDefinitionValidationException ex) { 86 throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex); 87 } 88 89 return exposedObject; 90 }
下面继续分析初始化一个Bean的流程，不太重要的流程就跳过了。
属性注入
属性注入的代码比较好找，可以看一下40行，取名为populateBean，即填充Bean的意思，看一下代码实现：
1 protected void populateBean(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw) { 2 PropertyValues pvs = mbd.getPropertyValues(); 3 4 if (bw == null) { 5 if (!pvs.isEmpty()) { 6 throw new BeanCreationException( 7 mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance"); 8 } 9 else { 10 // Skip property population phase for null instance. 11 return; 12 } 13 } 14 15 // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the 16 // state of the bean before properties are set. This can be used, for example, 17 // to support styles of field injection. 18 boolean continueWithPropertyPopulation = true; 19 20 if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { 21 for (BeanPostProcessor bp : getBeanPostProcessors()) { 22 if (bp instanceof InstantiationAwareBeanPostProcessor) { 23 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; 24 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { 25 continueWithPropertyPopulation = false; 26 break; 27 } 28 } 29 } 30 } 31 32 if (!continueWithPropertyPopulation) { 33 return; 34 } 35 36 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME || 37 mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { 38 MutablePropertyValues newPvs = new MutablePropertyValues(pvs); 39 40 // Add property values based on autowire by name if applicable. 41 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) { 42 autowireByName(beanName, mbd, bw, newPvs); 43 } 44 45 // Add property values based on autowire by type if applicable. 46 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { 47 autowireByType(beanName, mbd, bw, newPvs); 48 } 49 50 pvs = newPvs; 51 } 52 53 boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); 54 boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE); 55 56 if (hasInstAwareBpps || needsDepCheck) { 57 PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw); 58 if (hasInstAwareBpps) { 59 for (BeanPostProcessor bp : getBeanPostProcessors()) { 60 if (bp instanceof InstantiationAwareBeanPostProcessor) { 61 InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; 62 pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName); 63 if (pvs == null) { 64 return; 65 } 66 } 67 } 68 } 69 if (needsDepCheck) { 70 checkDependencies(beanName, mbd, filteredPds, pvs); 71 } 72 } 73 74 applyPropertyValues(beanName, mbd, bw, pvs); 75 }
这段代码层次有点深，跟一下74行的applyPropertyValues方法，最后那个pvs的实现类为MutablePropertyValues，里面持有一个List<PropertyValue>，每一个PropertyValue包含了此Bean属性的属性名与属性值。74行的代码实现为：
1 protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) { 2 if (pvs == null || pvs.isEmpty()) { 3 return; 4 } 5 6 MutablePropertyValues mpvs = null; 7 List<PropertyValue> original; 8 9 if (System.getSecurityManager()!= null) { 10 if (bw instanceof BeanWrapperImpl) { 11 ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext()); 12 } 13 } 14 15 if (pvs instanceof MutablePropertyValues) { 16 mpvs = (MutablePropertyValues) pvs; 17 if (mpvs.isConverted()) { 18 // Shortcut: use the pre-converted values as-is. 19 try { 20 bw.setPropertyValues(mpvs); 21 return; 22 } 23 catch (BeansException ex) { 24 throw new BeanCreationException( 25 mbd.getResourceDescription(), beanName, "Error setting property values", ex); 26 } 27 } 28 original = mpvs.getPropertyValueList(); 29 } 30 else { 31 original = Arrays.asList(pvs.getPropertyValues()); 32 } 33 34 TypeConverter converter = getCustomTypeConverter(); 35 if (converter == null) { 36 converter = bw; 37 } 38 BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter); 39 40 // Create a deep copy, resolving any references for values. 41 List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size()); 42 boolean resolveNecessary = false; 43 for (PropertyValue pv : original) { 44 if (pv.isConverted()) { 45 deepCopy.add(pv); 46 } 47 else { 48 String propertyName = pv.getName(); 49 Object originalValue = pv.getValue(); 50 Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue); 51 Object convertedValue = resolvedValue; 52 boolean convertible = bw.isWritableProperty(propertyName) && 53 !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName); 54 if (convertible) { 55 convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter); 56 } 57 // Possibly store converted value in merged bean definition, 58 // in order to avoid re-conversion for every created bean instance. 59 if (resolvedValue == originalValue) { 60 if (convertible) { 61 pv.setConvertedValue(convertedValue); 62 } 63 deepCopy.add(pv); 64 } 65 else if (convertible && originalValue instanceof TypedStringValue && 66 !((TypedStringValue) originalValue).isDynamic() && 67 !(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) { 68 pv.setConvertedValue(convertedValue); 69 deepCopy.add(pv); 70 } 71 else { 72 resolveNecessary = true; 73 deepCopy.add(new PropertyValue(pv, convertedValue)); 74 } 75 } 76 } 77 if (mpvs != null && !resolveNecessary) { 78 mpvs.setConverted(); 79 } 80 81 // Set our (possibly massaged) deep copy. 82 try { 83 bw.setPropertyValues(new MutablePropertyValues(deepCopy)); 84 } 85 catch (BeansException ex) { 86 throw new BeanCreationException( 87 mbd.getResourceDescription(), beanName, "Error setting property values", ex); 88 } 89 }
之后在第41行~第76行做了一次深拷贝（只是名字叫做深拷贝而已，其实就是遍历PropertyValue然后一个一个赋值到一个新的List而不是Java语义上的Clone，这里使用深拷贝是为了解析Values值中的所有引用），将PropertyValue一个一个赋值到一个新的List里面去，起名为deepCopy。最后执行83行进行复制，bw即BeanWrapper，持有Bean实例的一个Bean包装类，看一下代码实现：
1 public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid) 2 throws BeansException { 3 4 List<PropertyAccessException> propertyAccessExceptions = null; 5 List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ? 6 ((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues())); 7 for (PropertyValue pv : propertyValues) { 8 try { 9 // This method may throw any BeansException, which won\'t be caught 10 // here, if there is a critical failure such as no matching field. 11 // We can attempt to deal only with less serious exceptions. 12 setPropertyValue(pv); 13 } 14 catch (NotWritablePropertyException ex) { 15 if (!ignoreUnknown) { 16 throw ex; 17 } 18 // Otherwise, just ignore it and continue... 19 } 20 catch (NullValueInNestedPathException ex) { 21 if (!ignoreInvalid) { 22 throw ex; 23 } 24 // Otherwise, just ignore it and continue... 25 } 26 catch (PropertyAccessException ex) { 27 if (propertyAccessExceptions == null) { 28 propertyAccessExceptions = new LinkedList<PropertyAccessException>(); 29 } 30 propertyAccessExceptions.add(ex); 31 } 32 } 33 34 // If we encountered individual exceptions, throw the composite exception. 35 if (propertyAccessExceptions != null) { 36 PropertyAccessException[] paeArray = 37 propertyAccessExceptions.toArray(new PropertyAccessException[propertyAccessExceptions.size()]); 38 throw new PropertyBatchUpdateException(paeArray); 39 } 40 }
这段代码没什么特别的，遍历前面的deepCopy，拿每一个PropertyValue，执行第12行的setPropertyValue：
1 public void setPropertyValue(PropertyValue pv) throws BeansException { 2 PropertyTokenHolder tokens = (PropertyTokenHolder) pv.resolvedTokens; 3 if (tokens == null) { 4 String propertyName = pv.getName(); 5 BeanWrapperImpl nestedBw; 6 try { 7 nestedBw = getBeanWrapperForPropertyPath(propertyName); 8 } 9 catch (NotReadablePropertyException ex) { 10 throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName, 11 "Nested property in path \'" + propertyName + "\' does not exist", ex); 12 } 13 tokens = getPropertyNameTokens(getFinalPath(nestedBw, propertyName)); 14 if (nestedBw == this) { 15 pv.getOriginalPropertyValue().resolvedTokens = tokens; 16 } 17 nestedBw.setPropertyValue(tokens, pv); 18 } 19 else { 20 setPropertyValue(tokens, pv); 21 } 22 }
找一个合适的BeanWrapper，这里就是自身，然后执行17行的setPropertyValue方法进入最后一步，方法非常长，截取核心的一段：
1 final Method writeMethod = (pd instanceof GenericTypeAwarePropertyDescriptor ? 2 ((GenericTypeAwarePropertyDescriptor) pd).getWriteMethodForActualAccess() : 3 pd.getWriteMethod()); 4 if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers()) && !writeMethod.isAccessible()) { 5 if (System.getSecurityManager()!= null) { 6 AccessController.doPrivileged(new PrivilegedAction<Object>() { 7 public Object run() { 8 writeMethod.setAccessible(true); 9 return null; 10 } 11 }); 12 } 13 else { 14 writeMethod.setAccessible(true); 15 } 16 } 17 final Object value = valueToApply; 18 if (System.getSecurityManager() != null) { 19 try { 20 AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() { 21 public Object run() throws Exception { 22 writeMethod.invoke(object, value); 23 return null; 24 } 25 }, acc); 26 } 27 catch (PrivilegedActionException ex) { 28 throw ex.getException(); 29 } 30 } 31 else { 32 writeMethod.invoke(this.object, value); 33 }
大致流程就是两步：
（1）拿到写方法并将方法的可见性设置为true
（2）拿到Value值，对Bean通过反射调用写方法
这样完成了对于Bean属性值的设置。
Aware注入
接下来是Aware注入。在使用Spring的时候我们将自己的Bean实现BeanNameAware接口、BeanFactoryAware接口等，依赖容器帮我们注入当前Bean的名称或者Bean工厂，其代码实现先追溯到上面doCreateBean方法的42行initializeBean方法：
1 protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { 2 if (System.getSecurityManager() != null) { 3 AccessController.doPrivileged(new PrivilegedAction<Object>() { 4 public Object run() { 5 invokeAwareMethods(beanName, bean); 6 return null; 7 } 8 }, getAccessControlContext()); 9 } 10 else { 11 invokeAwareMethods(beanName, bean); 12 } 13 14 Object wrappedBean = bean; 15 if (mbd == null || !mbd.isSynthetic()) { 16 wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); 17 } 18 19 try { 20 invokeInitMethods(beanName, wrappedBean, mbd); 21 } 22 catch (Throwable ex) { 23 throw new BeanCreationException( 24 (mbd != null ? mbd.getResourceDescription() : null), 25 beanName, "Invocation of init method failed", ex); 26 } 27 28 if (mbd == null || !mbd.isSynthetic()) { 29 wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); 30 } 31 return wrappedBean; 32 }
看一下上面第5行的实现：
1 private void invokeAwareMethods(final String beanName, final以上是关于Spring源码分析非懒加载的Bean实例化过程（下篇）的主要内容，如果未能解决你的问题，请参考以下文章