Spring populateBean屬性賦值和自動註入
正文
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. //一、修改Bean實例 //給InstantiationAwareBeanPostProcessors最後一個機會在屬性設置前改變bean // 具體通過調用ibp.postProcessAfterInstantiation方法,如果調用返回false,表示不必繼續進行依賴註入,直接返回 if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; //返回值為true則繼續填充bean if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { return; } } } } PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null); // 根據bean的依賴註入方式:即是否標註有 @Autowired 註解或 autowire=“byType/byName” 的標簽 // 會遍歷bean中的屬性,根據類型或名稱來完成相應的註入 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. //二、根據名稱自動註入 if (resolvedAutowireMode == AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } // Add property values based on autowire by type if applicable. //三、根據類型自動註入 if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; } // 容器是否註冊瞭InstantiationAwareBeanPostProcessor boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); // 是否進行依賴檢查 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; PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName); if (pvsToUse == null) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); } //對所有需要依賴檢查的屬性進行後處理 //四、處理屬性值(@Autowired、@Value) pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName); if (pvsToUse == null) { return; } } pvs = pvsToUse; } } } // 檢查是否滿足相關依賴關系,對應的depends-on屬性,3.0後已棄用 if (needsDepCheck) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); } checkDependencies(beanName, mbd, filteredPds, pvs); } // 五、填充屬性 if (pvs != null) { applyPropertyValues(beanName, mbd, bw, pvs); } }
一、postProcessAfterInstantiation:修改Bean實例
在填充屬性之前調用postProcessAfterInstantiation修改Bean定義信息
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { return; } } } }
二、autowireByName:根據名稱自動註入
protected void autowireByName(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { //尋找bw中需要依賴註入的屬性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { //檢查緩存bean中是否存在當前bean if (containsBean(propertyName)) { //遞歸初始化相關的bean. 代碼(1) Object bean = getBean(propertyName); pvs.add(propertyName, bean); //註冊依賴 registerDependentBean(propertyName, beanName); if (logger.isTraceEnabled()) { logger.trace("Added autowiring by name from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + propertyName + "'"); } } else { // 找不到則不處理 if (logger.isTraceEnabled()) { logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName + "' by name: no matching bean found"); } } } }
三、autowireByType:根據類型自動註入
protected void autowireByType(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { // 獲取自定義的類型轉換器 TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } Set<String> autowiredBeanNames = new LinkedHashSet<>(4); //尋找bw中需要依賴註入的屬性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { try { // 獲取屬性描述符 PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName); //不要嘗試按類型為Object類型自動裝配:即使從技術上講是不滿意的,非簡單的屬性,也沒有意義。 if (Object.class != pd.getPropertyType()) { //探測指定屬性的set方法 MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd); // Do not allow eager init for type matching in case of a prioritized post-processor. boolean eager = !PriorityOrdered.class.isInstance(bw.getWrappedInstance()); DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager); //解析指定beanName的屬性所匹配的值,並把解析到的屬性名稱存儲在autowiredBeanNames中,當屬性存在多個封裝bean時 //比如: @Autowired private List<A> aList; 就會找到所有匹配A類型的bean並將其註入 Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter); if (autowiredArgument != null) { // 添加到待註入的bean列表中 pvs.add(propertyName, autowiredArgument); } for (String autowiredBeanName : autowiredBeanNames) { //註冊依賴 registerDependentBean(autowiredBeanName, beanName); if (logger.isTraceEnabled()) { logger.trace("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); } } }
四、postProcessPropertyValues:處理屬性值(@Resource、@Autowired、@Value)
CommonAnnotationBeanPostProcessor:處理@Resource
AutowiredAnnotationBeanPostProcessor:處理@Autowired、@Value。
詳情:https://www.jb51.net/article/277330.htm
五、applyPropertyValues:填充屬性
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) { if (pvs.isEmpty()) { return; } if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) { ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext()); } MutablePropertyValues mpvs = null; List<PropertyValue> original; if (pvs instanceof MutablePropertyValues) { mpvs = (MutablePropertyValues) pvs; //如果mpvs中的值已經被轉換為對應的類型那麼可以直接設置到beanWrapper 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並不是使用MutablePropertyValues封裝的類型,那麼直接使用原始的屬性獲取方法 original = Arrays.asList(pvs.getPropertyValues()); } TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } //獲取對應的解析器 BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter); // Create a deep copy, resolving any references for values. List<PropertyValue> deepCopy = new ArrayList<>(original.size()); boolean resolveNecessary = false; //遍歷屬性,將屬性轉換為對應屬性的類型 for (PropertyValue pv : original) { if (pv.isConverted()) { deepCopy.add(pv); } else { String propertyName = pv.getName(); Object originalValue = pv.getValue(); if (originalValue == AutowiredPropertyMarker.INSTANCE) { Method writeMethod = bw.getPropertyDescriptor(propertyName).getWriteMethod(); if (writeMethod == null) { throw new IllegalArgumentException("Autowire marker for property without write method: " + pv); } originalValue = new DependencyDescriptor(new MethodParameter(writeMethod, 0), true); } //解析、註入值 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 { bw.setPropertyValues(new MutablePropertyValues(deepCopy)); } catch (BeansException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Error setting property values", ex); } }
解析、註入值
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) { // We must check each value to see whether it requires a runtime reference // to another bean to be resolved. // 5.1 解析引用 if (value instanceof RuntimeBeanReference) { RuntimeBeanReference ref = (RuntimeBeanReference) value; return resolveReference(argName, ref); } // 如果根據另一個Bean的name進行依賴,進入下面的分支 else if (value instanceof RuntimeBeanNameReference) { String refName = ((RuntimeBeanNameReference) value).getBeanName(); refName = String.valueOf(doEvaluate(refName)); if (!this.beanFactory.containsBean(refName)) { throw new BeanDefinitionStoreException( "Invalid bean name '" + refName + "' in bean reference for " + argName); } return refName; } // 解析BeanDefinitionHolder else if (value instanceof BeanDefinitionHolder) { // Resolve BeanDefinitionHolder: contains BeanDefinition with name and aliases. BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value; return resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition()); } // 解析純BeanDefinition else if (value instanceof BeanDefinition) { // Resolve plain BeanDefinition, without contained name: use dummy name. BeanDefinition bd = (BeanDefinition) value; String innerBeanName = "(inner bean)" + BeanFactoryUtils.GENERATED_BEAN_NAME_SEPARATOR + ObjectUtils.getIdentityHexString(bd); return resolveInnerBean(argName, innerBeanName, bd); } // 解析數組 else if (value instanceof ManagedArray) { // May need to resolve contained runtime references. ManagedArray array = (ManagedArray) value; Class<?> elementType = array.resolvedElementType; if (elementType == null) { String elementTypeName = array.getElementTypeName(); if (StringUtils.hasText(elementTypeName)) { try { elementType = ClassUtils.forName(elementTypeName, this.beanFactory.getBeanClassLoader()); array.resolvedElementType = elementType; } catch (Throwable ex) { // Improve the message by showing the context. throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error resolving array type for " + argName, ex); } } else { elementType = Object.class; } } return resolveManagedArray(argName, (List<?>) value, elementType); } //5.2解析List else if (value instanceof ManagedList) { // May need to resolve contained runtime references. return resolveManagedList(argName, (List<?>) value); } // 解析Set else if (value instanceof ManagedSet) { // May need to resolve contained runtime references. return resolveManagedSet(argName, (Set<?>) value); } // 解析Map else if (value instanceof ManagedMap) { // May need to resolve contained runtime references. return resolveManagedMap(argName, (Map<?, ?>) value); } // 解析Properties else if (value instanceof ManagedProperties) { Properties original = (Properties) value; Properties copy = new Properties(); original.forEach((propKey, propValue) -> { if (propKey instanceof TypedStringValue) { propKey = evaluate((TypedStringValue) propKey); } if (propValue instanceof TypedStringValue) { propValue = evaluate((TypedStringValue) propValue); } if (propKey == null || propValue == null) { throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error converting Properties key/value pair for " + argName + ": resolved to null"); } copy.put(propKey, propValue); }); return copy; } // 解析String else if (value instanceof TypedStringValue) { // Convert value to target type here. TypedStringValue typedStringValue = (TypedStringValue) value; Object valueObject = evaluate(typedStringValue); try { Class<?> resolvedTargetType = resolveTargetType(typedStringValue); if (resolvedTargetType != null) { return this.typeConverter.convertIfNecessary(valueObject, resolvedTargetType); } else { return valueObject; } } catch (Throwable ex) { // Improve the message by showing the context. throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error converting typed String value for " + argName, ex); } } else if (value instanceof NullBean) { return null; } else { return evaluate(value); } }
5.1 解析依賴
核心還是getBean方法!開始觸發關聯創建Bean
private Object resolveReference(Object argName, RuntimeBeanReference ref) { try { Object bean; // 獲取BeanName String refName = ref.getBeanName(); refName = String.valueOf(doEvaluate(refName)); // 如果Bean在父容器,則去父容器取 if (ref.isToParent()) { if (this.beanFactory.getParentBeanFactory() == null) { throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Can't resolve reference to bean '" + refName + "' in parent factory: no parent factory available"); } bean = this.beanFactory.getParentBeanFactory().getBean(refName); } else { // 在本容器,調用getBean bean = this.beanFactory.getBean(refName); this.beanFactory.registerDependentBean(refName, this.beanName); } if (bean instanceof NullBean) { bean = null; } return bean; } catch (BeansException ex) { throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex); } }
5.2 解析List
直接把 List
集合塞入屬性中即可。
private List<?> resolveManagedList(Object argName, List<?> ml) { List<Object> resolved = new ArrayList<>(ml.size()); for (int i = 0; i < ml.size(); i++) { resolved.add(resolveValueIfNecessary(new KeyedArgName(argName, i), ml.get(i))); } return resolved; }
以上就是Spring populateBean屬性賦值和自動註入的詳細內容,更多關於Spring populateBean屬性的資料請關註WalkonNet其它相關文章!
推薦閱讀:
- Spring Bean的實例化之屬性註入源碼剖析過程
- 淺談一下Spring中的createBean
- Spring中Bean註入源碼示例解析
- 關於Spring Bean實例過程中使用反射和遞歸處理的Bean屬性填充問題
- 手把手帶你實現一個萌芽版的Spring容器