前面已經分析了Spring建立執行個體和解決循環依賴的問題，今天繼續看執行個體建立完成之後的操作，填充bean的屬性及應用生命周期接口
引
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args) throws BeanCreationException {
// Instantiate the bean.
// ① 執行個體化bean
BeanWrapper instanceWrapper = null;
// 注意factoryBeanInstanceCache是ConcurrentMap,remove方法會傳回删除的鍵值(如果不存在傳回null)
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
// 如果factoryBeanInstanceCache沒有緩存對應的BeanWrapper,則重新建立bean執行個體
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 允許MergedBeanDefinitionPostProcessor後處理器修改已合并的bean定義。
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 提前緩存ObjectFactory以解決bean之間的循環依賴
// mbd.isSingleton()->是否單例,Spring隻解決單例bean的循環依賴問題
// allowCircularReferences->是否允許循環依賴
// isSingletonCurrentlyInCreation->該bean是否建立中
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執行個體 這裡大家要與第①步區分開,到這裡bean已經完成了執行個體化,但是還沒有完成初始化的操作,例如bean的屬性填充
Object exposedObject = bean;
try {
// 填充bean屬性
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 循環依賴檢查
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 根據bean的作用域注冊bean
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
// ⑦ 傳回bean執行個體
return exposedObject;
}
第四步就是填充bean的屬性。我們來看其過程
1.屬性填充的準備工作
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
// ① 前置判斷
// 如果BeanWrapper對象為null,則說明沒有bean的執行個體
if (bw == null) {
// RootBeanDefinition中有屬性,但是bean的執行個體為空,抛出異常
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// RootBeanDefinition中沒有屬性,直接傳回
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 應用InstantiationAwareBeanPostProcessor處理器
// 在設定屬性之前,給InstantiationAwareBeanPostProcessor一個修改bean狀态的機會
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
// 是否繼續填充bean屬性
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
// ③ 如果InstantiationAwareBeanPostProcessor停止了對bean屬性的填充,則直接傳回
if (!continueWithPropertyPopulation) {
return;
}
// 擷取PropertyValues屬性
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
// ④ 解析自動裝配類型
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 判斷是否有InstantiationAwareBeanPostProcessors處理器,并進行處理
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 依賴檢查
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
// ⑦ 應用屬性
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
該方法最重要的就是對屬性填充方式判斷，byName，byType和不開啟自動注入。Spring預設是不開啟autowire的，需要在配置檔案中配置default-autowire屬性，那麼我們首先來分析不開啟自動注入方式的屬性填充。（byName，byType需要用到一些注解方面的知識，我們留在以後分析）
2.不開啟自動注入屬性填充
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
// 1、 如果PropertyValues為空,直接傳回
if (pvs.isEmpty()) {
return;
}
// 2、判斷安全管理器
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
}
//MutablePropertyValues是PropertyValues接口的預設實作類
MutablePropertyValues mpvs = null;
List<PropertyValue> original;
// 3、 擷取bean的屬性集合
// 如果pvs是MutablePropertyValues的執行個體,MutablePropertyValues是PropertyValues的預設實作
if (pvs instanceof MutablePropertyValues) {
// 将pvs轉換為MutablePropertyValues對象,并判斷mpvs是否已經經過轉換
mpvs = (MutablePropertyValues) pvs;
if (mpvs.isConverted()) {
// 如果pvs已經轉換過,則直接設定屬性值無需再次轉換
try {
bw.setPropertyValues(mpvs);
return;
}
catch (BeansException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
// 否則擷取原始PropertyValue集合
original = mpvs.getPropertyValueList();
}
else {
original = Arrays.asList(pvs.getPropertyValues());
}
// 4、 擷取類型轉換器
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// 5、 通過深度拷貝,解析值引用
List<PropertyValue> deepCopy = new ArrayList<>(original.size());
boolean resolveNecessary = false;
// 循環解析PropertyValues
for (PropertyValue pv : original) {
if (pv.isConverted()) {
deepCopy.add(pv);
}
else {
// 擷取屬性名稱
String propertyName = pv.getName();
// 擷取原始屬性值
Object originalValue = pv.getValue();
// 解析原始屬性值
// 當注入集合屬性時,如果指定了,value-type,如value-type="java.lang.String",
// 那麼resolveValueIfNecessary也會執行類型的轉換操作
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
Object convertedValue = resolvedValue;
// isWritableProperty-->判斷屬性是否可寫,如果屬性不存在傳回false
// isNestedOrIndexedProperty-->判斷是否索引屬性或者嵌套屬性
boolean convertible = bw.isWritableProperty(propertyName) && !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
if (convertible) {
// 類型轉換
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.
// 緩存已經轉換過的值,避免再次轉換
// 例如:當通過FactoryBean注入屬性值時 p:studentInfo="張三,25,三年二班",會有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、設定屬性值.
try {
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
2.1 步驟簡析
- 嘗試從緩存中中擷取已經解析過的屬性值
- 如果未能從緩存中擷取，則擷取原始的屬性值
- 擷取類型轉換器
- 循環所有原始屬性值，通過深度拷貝，解析值引用
- 解析原始屬性值
- 類型轉換
- 設定屬性值
我們隻分析其中的一些關鍵方法
2.2 resolveValueIfNecessary 解析屬性值
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// 1、 RuntimeBeanReference->運作時引用
// 例如BeanA依賴BeanB,那麼在配置檔案中有通過配置ref标簽進行引用的,在解析BeanDefinition的時候,是不會直接執行個體化BeanB的,那麼這個引用就是RuntimeBeanReference
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);
}
// 2、 RuntimeBeanNameReference->沒弄明白
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、 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、 解析字元串
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或者表達式
else if (value instanceof NullBean) {
return null;
}
else {
return evaluate(value);
}
}
該方法包含了對各種屬性值的解析，例如RuntimeBeanReference->運作時引用，我們已經在上一節分析過了。我們在對其中的解析List集合進行一下分析，篇幅優先其他的解析大家可以自行debug跟蹤分析。
解析List集合屬性，該方法也很簡單循環并再次調用resolveValueIfNecessary方法進行解析，将解析值加入List集合傳回即可。
private List<?> resolveManagedList(Object argName, List<?> ml) {
// 建立長度為配置檔案中指定的元素個數的List集合
List<Object> resolved = new ArrayList<>(ml.size());
for (int i = 0; i < ml.size(); i++) {
// 循環解析元素,如果配置檔案中指定了value-type,resolveValueIfNecessary過程中會對元素進行類型轉換
resolved.add(resolveValueIfNecessary(new KeyedArgName(argName, i), ml.get(i)));
}
return resolved;
}
2.3 convertForProperty 轉換屬性值
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);
}
}
調用convertForProperty方法執行轉換前的準本工作
public Object convertForProperty(@Nullable Object value, String propertyName) throws TypeMismatchException {
// CachedIntrospectionResults-->緩存了PropertyDescriptor集合
CachedIntrospectionResults cachedIntrospectionResults = getCachedIntrospectionResults();
// PropertyDescriptor-->表示JavaBean類通過存儲器導出一個屬性。主要方法：
// 1. getReadMethod()，獲得用于讀取屬性值的方法
// 2. getWriteMethod()，獲得用于寫入屬性值的方法
PropertyDescriptor pd = cachedIntrospectionResults.getPropertyDescriptor(propertyName);
if (pd == null) {
throw new InvalidPropertyException(getRootClass(), getNestedPath() + propertyName,"No property '" + propertyName + "' found");
}
// 擷取類型轉換上下文
TypeDescriptor td = cachedIntrospectionResults.getTypeDescriptor(pd);
if (td == null) {
// 如果未能從緩存中擷取,則建立一個新的TypeDescriptor并緩存
td = cachedIntrospectionResults.addTypeDescriptor(pd, new TypeDescriptor(property(pd)));
}
// 轉換類型
return convertForProperty(propertyName, null, value, td);
}
調用convertForProperty執行轉換，但是真正的轉換操作委托給了TypeConverterDelegate執行
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、判斷有無自定義屬性編輯器
PropertyEditor editor = this.propertyEditorRegistry.findCustomEditor(requiredType, propertyName);
ConversionFailedException conversionAttemptEx = null;
// No custom editor but custom ConversionService specified?
// 2、判斷有無自定義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)-->判斷requiredType和convertedValue的class,是否相同,
// 相同傳回->true;否則傳回->false
// 3、 如果有自定義屬性編輯器或者通過解析出來的值類型與真實的值類型的class不同
// 例如<property name="age" value="3"/>,我們需要将value轉換成int時
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、執行轉換
if (requiredType != null) {
// Try to apply some standard type conversion rules if appropriate.
if (convertedValue != null) {
// Object類型
if (Object.class == requiredType) {
return (T) convertedValue;
}
// 數組類型
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());
}
// 集合類型
else if (convertedValue instanceof Collection) {
// Convert elements to target type, if determined.
convertedValue = convertToTypedCollection((Collection<?>) convertedValue, propertyName, requiredType, typeDescriptor);
standardConversion = true;
}
// map類型
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:這裡是新開啟的if,不接上面的else if
// 如果經過轉換過的值是數組類型,且其長度隻有1,那麼隻取其第0個作為最終轉換值
if (convertedValue.getClass().isArray() && Array.getLength(convertedValue) == 1) {
convertedValue = Array.get(convertedValue, 0);
standardConversion = true;
}
// 如果類型是String,并且是java的基本資料類型或者包裝類型
// 包括 boolean, byte, char, short, int, long, float, double
// 和 Boolean, Byte, Character, Short, Integer, Long, Float, Double
// 那麼直接調用toString()方法傳回即可,注意convertedValue是Object類型,不是基本或包裝類型,是以是可以調用toString()方法的
if (String.class == requiredType && ClassUtils.isPrimitiveOrWrapper(convertedValue.getClass())) {
// We can stringify any primitive value...
return (T) convertedValue.toString();
}
// 如果轉換值是String類的執行個體,但是我們又不能轉換為解析出來的requiredType的執行個體
// 例如枚舉類型值的注入
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資訊
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;
}
// 數值類型
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是否可從convertedValue轉換而來,并嘗試使用conversionService轉換,及處理轉換異常
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);
}
}
// 到此為止,可以确定類型不比對,無法轉換,抛出IllegalArgumentException/IllegalStateException
StringBuilder msg = new StringBuilder();
msg.append("錯誤提示讓我删了...");
// 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、傳回轉換值
return (T) convertedValue;
}
2.4 setPropertyValues 設定屬性值
public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid) throws BeansException {
List<PropertyAccessException> propertyAccessExceptions = null;
// 擷取目前bean的所有屬性值
List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
// 循環并設定屬性值
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);
}
}
調用setPropertyValue設定單個屬性值
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);
}
}
調用nestedPa.setPropertyValue(tokens, pv);執行轉換前的判斷
protected void setPropertyValue(PropertyTokenHolder tokens, PropertyValue pv) throws BeansException {
// 設定配置檔案中的key:value對,例如.propertis中的屬性
if (tokens.keys != null) {
processKeyedProperty(tokens, pv);
}
// 設定本地屬性
else {
processLocalProperty(tokens, pv);
}
}
調動processLocalProperty設定本地屬性值
private void processLocalProperty(PropertyTokenHolder tokens, PropertyValue pv) {
PropertyHandler ph = getLocalPropertyHandler(tokens.actualName);
// PropertyHandler為null,或者方法不可寫的時候.
if (ph == null || !ph.isWritable()) {
//傳回是否為可選值，即在目标類上不存在相應的屬性時将被忽略。
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();
}
// 省略異常列印資訊...
catch (Exception ex) {}
}
valueToApply = convertForProperty(tokens.canonicalName, oldValue, originalValue, ph.toTypeDescriptor());
}
pv.getOriginalPropertyValue().conversionNecessary = (valueToApply != originalValue);
}
// 設定屬性值，即調用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);
// 通過Method的invoke方法設定屬性值，到這裡就會調動bean中的set方法，為bean設定屬性值
writeMethod.invoke(getWrappedInstance(), value);
}
}
3.initializeBean初始化bean
在完成bean屬性填充工作之後，距離bean執行個體的建立完成就不遠了。接下來調用initializeBean方法，完成有關bean的生命周期的部分操作，例如應用bean的處理器、調用bean的初始化方法、調用BeanNameAware接口等。
protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
// 1、調用各種AwareMethods
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareMethods(beanName, bean);
return null;
}, getAccessControlContext());
}
else {
invokeAwareMethods(beanName, bean);
}
// 2、應用bean前置處理器
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
// 3、調用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、應用bean後置處理器
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
在該方法中一共執行了四部操作，接下來我們逐漸分析其中的操作。
- 1、調用各種AwareMethods
/**
* 調用AwareMethods
* @param beanName
* @param bean
*/
private void invokeAwareMethods(final String beanName, final Object bean) {
if (bean instanceof Aware) {
// 1、調用BeanNameAware接口
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
// 2、調用BeanClassLoaderAware接口
if (bean instanceof BeanClassLoaderAware) {
ClassLoader bcl = getBeanClassLoader();
if (bcl != null) {
((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
}
}
// 3、調用BeanFactoryAware接口
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}
- 2、應用bean前置處理器
/**
* 在bean完成初始化之前應用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;
}
- 3、調用bean的init_method初始化方法
protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd) throws Throwable {
// 1、調用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、調用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);
}
}
}
具體的調用通過method.invoke方法執行，不再粘貼。
- 4、應用bean後置處理器
/**
* 在bean完成初始化之後應用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;
}
![23--Spring通過工廠方法執行個體化bean[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)