这篇文章主要介绍“Spring populateBean属性赋值和自动注入的方法是什么”，在日常操作中，相信很多人在Spring populateBean属性赋值和自动注入的方法是什么问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Spring populateBean属性赋值和自动注入的方法是什么”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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实例 //给InstantiationAwareBeanPostProcessors最后一个机会在属性设置前改变bean // 具体通过调用ibp.postProcessAfterInstantiation方法，如果调用返回false,表示不必继续进行依赖注入，直接返回 if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; //返回值为true则继续填充bean if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { return; } } } } PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null); // 根据bean的依赖注入方式：即是否标注有 @Autowired 注解或 autowire=“byType/byName” 的标签 // 会遍历bean中的属性，根据类型或名称来完成相应的注入 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、根据名称自动注入 if (resolvedAutowireMode == AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } // Add property values based on autowire by type if applicable. //三、根据类型自动注入 if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; } // 容器是否注册了InstantiationAwareBeanPostProcessor boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); // 是否进行依赖检查 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); } //对所有需要依赖检查的属性进行后处理 //四、处理属性值（@Autowired、@Value） pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName); if (pvsToUse == null) { return; } } pvs = pvsToUse; } } } // 检查是否满足相关依赖关系，对应的depends-on属性，3.0后已弃用 if (needsDepCheck) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); } checkDependencies(beanName, mbd, filteredPds, pvs); } // 五、填充属性 if (pvs != null) { applyPropertyValues(beanName, mbd, bw, pvs); }}一、postProcessAfterInstantiation：修改Bean实例
在填充属性之前调用postProcessAfterInstantiation修改Bean定义信息
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：根据名称自动注入
protected void autowireByName(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { //寻找bw中需要依赖注入的属性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { //检查缓存bean中是否存在当前bean if (containsBean(propertyName)) { //递归初始化相关的bean. 代码(1) Object bean = getBean(propertyName); pvs.add(propertyName, bean); //注册依赖 registerDependentBean(propertyName, beanName); if (logger.isTraceEnabled()) { logger.trace("Added autowiring by name from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + propertyName + "'"); } } else { // 找不到则不处理 if (logger.isTraceEnabled()) { logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName + "' by name: no matching bean found"); } } }}三、autowireByType：根据类型自动注入
protected void autowireByType(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { // 获取自定义的类型转换器 TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } Set<String> autowiredBeanNames = new LinkedHashSet<>(4); //寻找bw中需要依赖注入的属性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { try { // 获取属性描述符 PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName); //不要尝试按类型为Object类型自动装配：即使从技术上讲是不满意的，非简单的属性，也没有意义。 if (Object.class != pd.getPropertyType()) { //探测指定属性的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的属性所匹配的值,并把解析到的属性名称存储在autowiredBeanNames中,当属性存在多个封装bean时 //比如: @Autowired private List<A> aList; 就会找到所有匹配A类型的bean并将其注入 Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter); if (autowiredArgument != null) { // 添加到待注入的bean列表中 pvs.add(propertyName, autowiredArgument); } for (String autowiredBeanName : autowiredBeanNames) { //注册依赖 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：处理属性值（@Resource、@Autowired、@Value）
CommonAnnotationBeanPostProcessor：处理@Resource
AutowiredAnnotationBeanPostProcessor：处理@Autowired、@Value。
详情：https://www.yisu.com/article/277330.htm
五、applyPropertyValues：填充属性
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中的值已经被转换为对应的类型那么可以直接设置到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<>(original.size()); boolean resolveNecessary = false; //遍历属性,将属性转换为对应属性的类型 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、注入值 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、注入值
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); } // 如果根据另一个Bean的name进行依赖，进入下面的分支 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()); } // 解析纯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); } // 解析数组 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 解析依赖
核心还是getBean方法！开始触发关联创建Bean
private Object resolveReference(Object argName, RuntimeBeanReference ref) { try { Object bean; // 获取BeanName String refName = ref.getBeanName(); refName = String.valueOf(doEvaluate(refName)); // 如果Bean在父容器，则去父容器取 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，调用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 集合塞入属性中即可。
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;}到此，关于“Spring populateBean属性赋值和自动注入的方法是什么”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注编程网网站，小编会继续努力为大家带来更多实用的文章！
