Spring5源码（25）-Spring填充bean属性及应用生命周期接口

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args) throws BeanCreationException {
    // Instantiate the bean.
    // ① 实例化bean
    BeanWrapper instanceWrapper = null;
    // 注意factoryBeanInstanceCache是ConcurrentMap,remove方法会返回删除的键值(如果不存在返回null)
    if (mbd.isSingleton()) {
        instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
    }
    // 如果factoryBeanInstanceCache没有缓存对应的BeanWrapper,则重新创建bean实例
    if (instanceWrapper == null) {
        instanceWrapper = createBeanInstance(beanName, mbd, args);
    }
    final Object bean = instanceWrapper.getWrappedInstance();
    Class<?> beanType = instanceWrapper.getWrappedClass();
    if (beanType != NullBean.class) {
        mbd.resolvedTargetType = beanType;
    }
    // Allow post-processors to modify the merged bean definition.
    // ② 允许MergedBeanDefinitionPostProcessor后处理器修改已合并的bean定义。
    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;
        }
    }
    // Eagerly cache singletons to be able to resolve circular references
    // even when triggered by lifecycle interfaces like BeanFactoryAware.
    // ③ 提前缓存ObjectFactory以解决bean之间的循环依赖
    // mbd.isSingleton()->是否单例,Spring只解决单例bean的循环依赖问题
    // allowCircularReferences->是否允许循环依赖
    // isSingletonCurrentlyInCreation->该bean是否创建中
    boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName));
    if (earlySingletonExposure) {
        addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
    }
    // Initialize the bean instance.
    // ④ 初始化bean实例 这里大家要与第①步区分开,到这里bean已经完成了实例化,但是还没有完成初始化的操作,例如bean的属性填充
    Object exposedObject = bean;
    try {
        // 填充bean属性
        populateBean(beanName, mbd, instanceWrapper);
        // 初始化bean
        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);
        }
    }
    // ⑤ 循环依赖检查
    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<>(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 {
        // ⑥ 根据bean的作用域注册bean
        registerDisposableBeanIfNecessary(beanName, bean, mbd);
    }
    catch (BeanDefinitionValidationException ex) {
        throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
    }
    // ⑦ 返回bean实例
    return exposedObject;
}

protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
    // ① 前置判断
    // 如果BeanWrapper对象为null,则说明没有bean的实例
    if (bw == null) {
        // RootBeanDefinition中有属性,但是bean的实例为空,抛出异常
        if (mbd.hasPropertyValues()) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
        }
        else {
            // RootBeanDefinition中没有属性,直接返回
            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.
    // ② 应用InstantiationAwareBeanPostProcessor处理器
    // 在设置属性之前,给InstantiationAwareBeanPostProcessor一个修改bean状态的机会
    boolean continueWithPropertyPopulation = true;
    if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
        for (BeanPostProcessor bp : getBeanPostProcessors()) {
            if (bp instanceof InstantiationAwareBeanPostProcessor) {
                InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
                // 是否继续填充bean属性
                if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
                    continueWithPropertyPopulation = false;
                    break;
                }
            }
        }
    }
    // ③ 如果InstantiationAwareBeanPostProcessor停止了对bean属性的填充,则直接返回
    if (!continueWithPropertyPopulation) {
        return;
    }
    // 获取PropertyValues属性
    PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
    // ④ 解析自动装配类型
    if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
        MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
        // byName注入
        if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
            autowireByName(beanName, mbd, bw, newPvs);
        }
        // byType注入
        if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
            autowireByType(beanName, mbd, bw, newPvs);
        }
        pvs = newPvs;
    }
    // ⑤ 判断是否有InstantiationAwareBeanPostProcessors处理器,并进行处理
    boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
    boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.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);
                    }
                    pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
                    if (pvsToUse == null) {
                        return;
                    }
                }
                pvs = pvsToUse;
            }
        }
    }
    // ⑥ 依赖检查
    if (needsDepCheck) {
        if (filteredPds == null) {
            filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
        }
        checkDependencies(beanName, mbd, filteredPds, pvs);
    }
    // ⑦ 应用属性
    if (pvs != null) {
        applyPropertyValues(beanName, mbd, bw, pvs);
    }
}

protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
    // 1、 如果PropertyValues为空,直接返回
    if (pvs.isEmpty()) {
        return;
    }
    // 2、判断安全管理器
    if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
        ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
    }
    //MutablePropertyValues是PropertyValues接口的默认实现类
    MutablePropertyValues mpvs = null;
    List<PropertyValue> original;
    // 3、 获取bean的属性集合
    // 如果pvs是MutablePropertyValues的实例,MutablePropertyValues是PropertyValues的默认实现
    if (pvs instanceof MutablePropertyValues) {
        // 将pvs转换为MutablePropertyValues对象,并判断mpvs是否已经经过转换
        mpvs = (MutablePropertyValues) pvs;
        if (mpvs.isConverted()) {
            // 如果pvs已经转换过,则直接设置属性值无需再次转换
            try {
                bw.setPropertyValues(mpvs);
                return;
            }
            catch (BeansException ex) {
                throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", ex);
            }
        }
        // 否则获取原始PropertyValue集合
        original = mpvs.getPropertyValueList();
    }
    else {
        original = Arrays.asList(pvs.getPropertyValues());
    }
    // 4、 获取类型转换器
    TypeConverter converter = getCustomTypeConverter();
    if (converter == null) {
        converter = bw;
    }
    BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
    // 5、 通过深度拷贝,解析值引用
    List<PropertyValue> deepCopy = new ArrayList<>(original.size());
    boolean resolveNecessary = false;
    // 循环解析PropertyValues
    for (PropertyValue pv : original) {
        if (pv.isConverted()) {
            deepCopy.add(pv);
        }
        else {
            // 获取属性名称
            String propertyName = pv.getName();
            // 获取原始属性值
            Object originalValue = pv.getValue();
            // 解析原始属性值
            // 当注入集合属性时,如果指定了,value-type,如value-type="java.lang.String",
            // 那么resolveValueIfNecessary也会执行类型的转换操作
            Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
            Object convertedValue = resolvedValue;
            // isWritableProperty-->判断属性是否可写,如果属性不存在返回false
            // isNestedOrIndexedProperty-->判断是否索引属性或者嵌套属性
            boolean convertible = bw.isWritableProperty(propertyName) && !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
            if (convertible) {
                // 类型转换
                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.
            // 缓存已经转换过的值,避免再次转换
            // 例如:当通过FactoryBean注入属性值时 p:studentInfo="张三,25,三年二班",会有resolvedValue == originalValue
            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();
    }
    // 7、设置属性值.
    try {
        bw.setPropertyValues(new MutablePropertyValues(deepCopy));
    }
    catch (BeansException ex) {
        throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", ex);
    }
}

public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
    // 1、 RuntimeBeanReference->运行时引用
    //   例如BeanA依赖BeanB,那么在配置文件中有通过配置ref标签进行引用的,在解析BeanDefinition的时候,是不会直接实例化BeanB的,那么这个引用就是RuntimeBeanReference
    if (value instanceof RuntimeBeanReference) {
        RuntimeBeanReference ref = (RuntimeBeanReference) value;
        return resolveReference(argName, ref);
    }
    // 2、 RuntimeBeanNameReference->没弄明白
    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;
    }
    // 3、 解析innerBean
    else if (value instanceof BeanDefinitionHolder) {
        // Resolve BeanDefinitionHolder: contains BeanDefinition with name and aliases.
        BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value;
        return resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition());
    }
    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);
    }
    // 4、 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、 解析List集合
    else if (value instanceof ManagedList) {
        // May need to resolve contained runtime references.
        return resolveManagedList(argName, (List<?>) value);
    }
    // 6、 解析Set集合
    else if (value instanceof ManagedSet) {
        // May need to resolve contained runtime references.
        return resolveManagedSet(argName, (Set<?>) value);
    }
    // 7、 解析Map集合
    else if (value instanceof ManagedMap) {
        // May need to resolve contained runtime references.
        return resolveManagedMap(argName, (Map<?, ?>) value);
    }
    // 8、 解析Properties集合
    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;
    }
    // 9、 解析字符串
    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);
        }
    }
    // 10、 NullBean或者表达式
    else if (value instanceof NullBean) {
        return null;
    }
    else {
        return evaluate(value);
    }
}

private List<?> resolveManagedList(Object argName, List<?> ml) {
    // 创建长度为配置文件中指定的元素个数的List集合
    List<Object> resolved = new ArrayList<>(ml.size());
    for (int i = 0; i < ml.size(); i++) {
        // 循环解析元素,如果配置文件中指定了value-type,resolveValueIfNecessary过程中会对元素进行类型转换
        resolved.add(resolveValueIfNecessary(new KeyedArgName(argName, i), ml.get(i)));
    }
    return resolved;
}

private Object convertForProperty(@Nullable Object value, String propertyName, BeanWrapper bw, TypeConverter converter) {
    if (converter instanceof BeanWrapperImpl) {
        return ((BeanWrapperImpl) converter).convertForProperty(value, propertyName);
    }
    else {
        PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
        MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
        return converter.convertIfNecessary(value, pd.getPropertyType(), methodParam);
    }
}

public Object convertForProperty(@Nullable Object value, String propertyName) throws TypeMismatchException {
    // CachedIntrospectionResults-->缓存了PropertyDescriptor集合
    CachedIntrospectionResults cachedIntrospectionResults = getCachedIntrospectionResults();
    // PropertyDescriptor-->表示JavaBean类通过存储器导出一个属性。主要方法：
    // 1. getReadMethod()，获得用于读取属性值的方法
    // 2. getWriteMethod()，获得用于写入属性值的方法
    PropertyDescriptor pd = cachedIntrospectionResults.getPropertyDescriptor(propertyName);
    if (pd == null) {
        throw new InvalidPropertyException(getRootClass(), getNestedPath() + propertyName,"No property '" + propertyName + "' found");
    }
    // 获取类型转换上下文
    TypeDescriptor td = cachedIntrospectionResults.getTypeDescriptor(pd);
    if (td == null) {
        // 如果未能从缓存中获取,则创建一个新的TypeDescriptor并缓存
        td = cachedIntrospectionResults.addTypeDescriptor(pd, new TypeDescriptor(property(pd)));
    }
    // 转换类型
    return convertForProperty(propertyName, null, value, td);
}

public <T> T convertIfNecessary(@Nullable String propertyName, @Nullable Object oldValue, @Nullable Object newValue,
            @Nullable Class<T> requiredType, @Nullable TypeDescriptor typeDescriptor) throws IllegalArgumentException {
    // Custom editor for this type?
    // 1、判断有无自定义属性编辑器
    PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);
    ConversionFailedException conversionAttemptEx = null;
    // No custom editor but custom ConversionService specified?
    // 2、判断有无自定义ConversionService
    ConversionService conversionService = this.propertyEditorRegistry.getConversionService();
    if (editor == null && conversionService != null && newValue != null && typeDescriptor != null) {
        TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue);
        if (conversionService.canConvert(sourceTypeDesc, typeDescriptor)) {
            try {
                return (T) conversionService.convert(newValue, sourceTypeDesc, typeDescriptor);
            }
            catch (ConversionFailedException ex) {
                // fallback to default conversion logic below
                conversionAttemptEx = ex;
            }
        }
    }
    Object convertedValue = newValue;
    // Value not of required type?
    // ClassUtils.isAssignableValue(requiredType, convertedValue)-->判断requiredType和convertedValue的class,是否相同,
    // 相同返回->true;否则返回->false
    // 3、 如果有自定义属性编辑器或者通过解析出来的值类型与真实的值类型的class不同
    // 例如<property name="age" value="3"/>,我们需要将value转换成int时
    if (editor != null || (requiredType != null && !ClassUtils.isAssignableValue(requiredType, convertedValue))) {
        if (typeDescriptor != null && requiredType != null && Collection.class.isAssignableFrom(requiredType) && convertedValue instanceof String) {
            TypeDescriptor elementTypeDesc = typeDescriptor.getElementTypeDescriptor();
            if (elementTypeDesc != null) {
                Class<?> elementType = elementTypeDesc.getType();
                if (Class.class == elementType || Enum.class.isAssignableFrom(elementType)) {
                    convertedValue = StringUtils.commaDelimitedListToStringArray((String) convertedValue);
                }
            }
        }
        if (editor == null) {
            editor = findDefaultEditor(requiredType);
        }
        convertedValue = doConvertValue(oldValue, convertedValue, requiredType, editor);
    }
    boolean standardConversion = false;
    // 4、执行转换
    if (requiredType != null) {
        // Try to apply some standard type conversion rules if appropriate.
        if (convertedValue != null) {
            // Object类型
            if (Object.class == requiredType) {
                return (T) convertedValue;
            }
            // 数组类型
            else if (requiredType.isArray()) {
                // Array required -> apply appropriate conversion of elements.
                if (convertedValue instanceof String && Enum.class.isAssignableFrom(requiredType.getComponentType())) {
                    convertedValue = StringUtils.commaDelimitedListToStringArray((String) convertedValue);
                }
                return (T) convertToTypedArray(convertedValue, propertyName, requiredType.getComponentType());
            }
            // 集合类型
            else if (convertedValue instanceof Collection) {
                // Convert elements to target type, if determined.
                convertedValue = convertToTypedCollection((Collection<?>) convertedValue, propertyName, requiredType, typeDescriptor);
                standardConversion = true;
            }
            // map类型
            else if (convertedValue instanceof Map) {
                // Convert keys and values to respective target type, if determined.
                convertedValue = convertToTypedMap((Map<?, ?>) convertedValue, propertyName, requiredType, typeDescriptor);
                standardConversion = true;
            }
            // 注意:这里是新开启的if,不接上面的else if
            // 如果经过转换过的值是数组类型,且其长度只有1,那么只取其第0个作为最终转换值
            if (convertedValue.getClass().isArray() && Array.getLength(convertedValue) == 1) {
                convertedValue = Array.get(convertedValue, 0);
                standardConversion = true;
            }
            // 如果类型是String,并且是java的基本数据类型或者包装类型
            // 包括 boolean, byte, char, short, int, long, float, double
            // 和 Boolean, Byte, Character, Short, Integer, Long, Float, Double
            // 那么直接调用toString()方法返回即可,注意convertedValue是Object类型,不是基本或包装类型,所以是可以调用toString()方法的
            if (String.class == requiredType && ClassUtils.isPrimitiveOrWrapper(convertedValue.getClass())) {
                // We can stringify any primitive value...
                return (T) convertedValue.toString();
            }
            // 如果转换值是String类的实例,但是我们又不能转换为解析出来的requiredType的实例
            // 例如枚举类型值的注入
            else if (convertedValue instanceof String && !requiredType.isInstance(convertedValue)) {
                if (conversionAttemptEx == null && !requiredType.isInterface() && !requiredType.isEnum()) {
                    try {
                        Constructor<T> strCtor = requiredType.getConstructor(String.class);
                        return BeanUtils.instantiateClass(strCtor, convertedValue);
                    }
                    // 删除logger信息
                    catch (NoSuchMethodException ex) {}
                    catch (Exception ex) {}
                }
                String trimmedValue = ((String) convertedValue).trim();
                if (requiredType.isEnum() && "".equals(trimmedValue)) {
                    // It's an empty enum identifier: reset the enum value to null.
                    return null;
                }
                convertedValue = attemptToConvertStringToEnum(requiredType, trimmedValue, convertedValue);
                standardConversion = true;
            }
            // 数值类型
            else if (convertedValue instanceof Number && Number.class.isAssignableFrom(requiredType)) {
                convertedValue = NumberUtils.convertNumberToTargetClass((Number) convertedValue, (Class<Number>) requiredType);
                standardConversion = true;
            }
        }
        else {
            // convertedValue == null
            if (requiredType == Optional.class) {
                convertedValue = Optional.empty();
            }
        }
        // 5、 判定requiredType是否可从convertedValue转换而来,并尝试使用conversionService转换,及处理转换异常
        if (!ClassUtils.isAssignableValue(requiredType, convertedValue)) {
            if (conversionAttemptEx != null) {
                // Original exception from former ConversionService call above...
                throw conversionAttemptEx;
            }
            else if (conversionService != null && typeDescriptor != null) {
                // ConversionService not tried before, probably custom editor found
                // but editor couldn't produce the required type...
                TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue);
                if (conversionService.canConvert(sourceTypeDesc, typeDescriptor)) {
                    return (T) conversionService.convert(newValue, sourceTypeDesc, typeDescriptor);
                }
            }
            // 到此为止,可以确定类型不匹配,无法转换,抛出IllegalArgumentException/IllegalStateException
            StringBuilder msg = new StringBuilder();
            msg.append("错误提示让我删了...");
            // 删除了msg提示配置
            if (editor != null) {
                throw new IllegalArgumentException(msg.toString());
            }
            else {
                throw new IllegalStateException(msg.toString());
            }
        }
    }
    if (conversionAttemptEx != null) {
        if (editor == null && !standardConversion && requiredType != null && Object.class != requiredType) {
            throw conversionAttemptEx;
        }
    }
    // 6、返回转换值
    return (T) convertedValue;
}

public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid) throws BeansException {
    List<PropertyAccessException> propertyAccessExceptions = null;
    // 获取当前bean的所有属性值
    List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
            ((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
    // 循环并设置属性值
    for (PropertyValue pv : propertyValues) {
        try {
            // This method may throw any BeansException, which won't be caught
            // here, if there is a critical failure such as no matching field.
            // We can attempt to deal only with less serious exceptions.
            setPropertyValue(pv);
        }
        catch (NotWritablePropertyException ex) {
            if (!ignoreUnknown) {
                throw ex;
            }
            // Otherwise, just ignore it and continue...
        }
        catch (NullValueInNestedPathException ex) {
            if (!ignoreInvalid) {
                throw ex;
            }
            // Otherwise, just ignore it and continue...
        }
        catch (PropertyAccessException ex) {
            if (propertyAccessExceptions == null) {
                propertyAccessExceptions = new ArrayList<>();
            }
            propertyAccessExceptions.add(ex);
        }
    }
    // If we encountered individual exceptions, throw the composite exception.
    if (propertyAccessExceptions != null) {
        PropertyAccessException[] paeArray = propertyAccessExceptions.toArray(new PropertyAccessException[0]);
        throw new PropertyBatchUpdateException(paeArray);
    }
}

public void setPropertyValue(PropertyValue pv) throws BeansException {
    PropertyTokenHolder tokens = (PropertyTokenHolder) pv.resolvedTokens;
    if (tokens == null) {
        String propertyName = pv.getName();
        AbstractNestablePropertyAccessor nestedPa;
        try {
            nestedPa = getPropertyAccessorForPropertyPath(propertyName);
        }
        catch (NotReadablePropertyException ex) {
            throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
                    "Nested property in path '" + propertyName + "' does not exist", ex);
        }
        tokens = getPropertyNameTokens(getFinalPath(nestedPa, propertyName));
        if (nestedPa == this) {
            pv.getOriginalPropertyValue().resolvedTokens = tokens;
        }
        nestedPa.setPropertyValue(tokens, pv);
    }
    else {
        setPropertyValue(tokens, pv);
    }
}

protected void setPropertyValue(PropertyTokenHolder tokens, PropertyValue pv) throws BeansException {
    // 设置配置文件中的key:value对,例如.propertis中的属性
    if (tokens.keys != null) {
        processKeyedProperty(tokens, pv);
    }
    // 设置本地属性
    else {
        processLocalProperty(tokens, pv);
    }
}

private void processLocalProperty(PropertyTokenHolder tokens, PropertyValue pv) {
    PropertyHandler ph = getLocalPropertyHandler(tokens.actualName);
    // PropertyHandler为null,或者方法不可写的时候.
    if (ph == null || !ph.isWritable()) {
        //返回是否为可选值，即在目标类上不存在相应的属性时将被忽略。
        if (pv.isOptional()) {
            return;
        }
        else {
            throw createNotWritablePropertyException(tokens.canonicalName);
        }
    }
    Object oldValue = null;
    try {
        Object originalValue = pv.getValue();
        Object valueToApply = originalValue;
        if (!Boolean.FALSE.equals(pv.conversionNecessary)) {
            if (pv.isConverted()) {
                valueToApply = pv.getConvertedValue();
            }
            else {
                if (isExtractOldValueForEditor() && ph.isReadable()) {
                    try {
                        oldValue = ph.getValue();
                    }
                    // 省略异常打印信息...
                    catch (Exception ex) {}
                }
                valueToApply = convertForProperty(tokens.canonicalName, oldValue, originalValue, ph.toTypeDescriptor());
            }
            pv.getOriginalPropertyValue().conversionNecessary = (valueToApply != originalValue);
        }
        // 设置属性值，即调用bean中的set方法
        ph.setValue(valueToApply);
    }
    catch (TypeMismatchException ex) {
        throw ex;
    }
    catch (InvocationTargetException ex) {
        PropertyChangeEvent propertyChangeEvent = new PropertyChangeEvent(
                getRootInstance(), this.nestedPath + tokens.canonicalName, oldValue, pv.getValue());
        if (ex.getTargetException() instanceof ClassCastException) {
            throw new TypeMismatchException(propertyChangeEvent, ph.getPropertyType(), ex.getTargetException());
        }
        else {
            Throwable cause = ex.getTargetException();
            if (cause instanceof UndeclaredThrowableException) {
                // May happen e.g. with Groovy-generated methods
                cause = cause.getCause();
            }
            throw new MethodInvocationException(propertyChangeEvent, cause);
        }
    }
    catch (Exception ex) {
        PropertyChangeEvent pce = new PropertyChangeEvent(getRootInstance(), this.nestedPath + tokens.canonicalName, oldValue, pv.getValue());
        throw new MethodInvocationException(pce, ex);
    }
}

public void setValue(final @Nullable Object value) throws Exception {
    final Method writeMethod = (this.pd instanceof GenericTypeAwarePropertyDescriptor ?
            ((GenericTypeAwarePropertyDescriptor) this.pd).getWriteMethodForActualAccess() :
            this.pd.getWriteMethod());
    if (System.getSecurityManager() != null) {
        AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
            ReflectionUtils.makeAccessible(writeMethod);
            return null;
        });
        try {
            AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->
                    writeMethod.invoke(getWrappedInstance(), value), acc);
        }
        catch (PrivilegedActionException ex) {
            throw ex.getException();
        }
    }
    else {
        ReflectionUtils.makeAccessible(writeMethod);
        // 通过Method的invoke方法设置属性值，到这里就会调动bean中的set方法，为bean设置属性值
        writeMethod.invoke(getWrappedInstance(), value);
    }
}

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
    // 1、调用各种AwareMethods
    if (System.getSecurityManager() != null) {
        AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
            invokeAwareMethods(beanName, bean);
            return null;
        }, getAccessControlContext());
    }
    else {
        invokeAwareMethods(beanName, bean);
    }
    // 2、应用bean前置处理器
    Object wrappedBean = bean;
    if (mbd == null || !mbd.isSynthetic()) {
        wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
    }
    // 3、调用bean的init_method初始化方法
    try {
        invokeInitMethods(beanName, wrappedBean, mbd);
    }
    catch (Throwable ex) {
        throw new BeanCreationException((mbd != null ? mbd.getResourceDescription() : null),beanName,"Invocation of init method failed", ex);
    }
    // 4、应用bean后置处理器
    if (mbd == null || !mbd.isSynthetic()) {
        wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    }
    return wrappedBean;
}

/**
 * 调用AwareMethods
 * @param beanName
 * @param bean
 */
private void invokeAwareMethods(final String beanName, final Object bean) {
    if (bean instanceof Aware) {
        // 1、调用BeanNameAware接口
        if (bean instanceof BeanNameAware) {
            ((BeanNameAware) bean).setBeanName(beanName);
        }
        // 2、调用BeanClassLoaderAware接口
        if (bean instanceof BeanClassLoaderAware) {
            ClassLoader bcl = getBeanClassLoader();
            if (bcl != null) {
                ((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
            }
        }
        // 3、调用BeanFactoryAware接口
        if (bean instanceof BeanFactoryAware) {
            ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
        }
    }
}

/**
 * 在bean完成初始化之前应用BeanPostProcessors
 * @param existingBean the new bean instance
 * @param beanName the name of the bean
 * @return
 * @throws BeansException
 */
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName) throws BeansException {
    Object result = existingBean;
    for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
        Object current = beanProcessor.postProcessBeforeInitialization(result, beanName);
        if (current == null) {
            return result;
        }
        result = current;
    }
    return result;
}

protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd) throws Throwable {
    // 1、调用InitializingBean接口
    boolean isInitializingBean = (bean instanceof InitializingBean);
    if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
        if (System.getSecurityManager() != null) {
            try {
                AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
                    ((InitializingBean) bean).afterPropertiesSet();
                    return null;
                }, getAccessControlContext());
            }
            catch (PrivilegedActionException pae) {
                throw pae.getException();
            }
        }
        else {
            ((InitializingBean) bean).afterPropertiesSet();
        }
    }
    // 2、调用init-method
    if (mbd != null && bean.getClass() != NullBean.class) {
        String initMethodName = mbd.getInitMethodName();
        if (StringUtils.hasLength(initMethodName) &&
                !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
                !mbd.isExternallyManagedInitMethod(initMethodName)) {
            invokeCustomInitMethod(beanName, bean, mbd);
        }
    }
}

/**
 * 在bean完成初始化之后应用BeanPostProcessors
 * @param existingBean the new bean instance
 * @param beanName the name of the bean
 * @return
 * @throws BeansException
 */
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName) throws BeansException {
    Object result = existingBean;
    for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
        Object current = beanProcessor.postProcessAfterInitialization(result, beanName);
        if (current == null) {
            return result;
        }
        result = current;
    }
    return result;
}