protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
//这里取得在BeanDefinition中设置的property值，这些property来自对BeanDefinition的解析
//具体的解析过程可以参看载入和解析BeanDefinitoin的分析
PropertyValues pvs = mbd.getPropertyValues();
if (bw == null) {
if (!pvs.isEmpty()) {
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.
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
//这里对autowire注入的处理，可以根据Bean的名称或者类型来完成Bean的autowire
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
if (hasInstAwareBpps || needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
if (hasInstAwareBpps) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvs == null) {
return;
}
}
}
}
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
}
//对属性进行注入
applyPropertyValues(beanName, mbd, bw, pvs);
}
//通过applyPropertyValues了解具体的对属性进行解析然后注入的过程
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs == null || 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;
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 {
original = Arrays.asList(pvs.getPropertyValues());
}
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
//BeanDefinitionValueResolver对BeanDefinition的解析在这个valueResolver中完成
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// Create a deep copy, resolving any references for values.
//这里为解析值创建一个副本，副本中的数据将会被注入到Bean中
List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size());
boolean resolveNecessary = false;
for (PropertyValue pv : original) {
if (pv.isConverted()) {
deepCopy.add(pv);
}
else {
String propertyName = pv.getName();
Object originalValue = pv.getValue();
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.
//这里是依赖注入发生的地方，会在AbstractNestablePropertyAccessor中完成
try {
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}这里通过使用BeanDefinitionValueResolver来对BeanDefinition进行解析，然后注入到property中。具体的对Bean reference进行解析的过程如代码所示:
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
try {
//从RuntimeBeanReference取得reference的名字，
// 这个RuntimeBeanReference是在载入BeanDefinition时根据配置生成
String refName = ref.getBeanName();
refName = String.valueOf(doEvaluate(refName));
//如果ref是在双亲IoC容器中，那就到双亲IoC容器中去获取
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");
}
return this.beanFactory.getParentBeanFactory().getBean(refName);
}
//在当前IoC容器中获取Bean，这里会触发一个getBean的过程，
// 如果依赖注入没有发生，这里会触发相应的依赖注入的发生
else {
Object bean = this.beanFactory.getBean(refName);
this.beanFactory.registerDependentBean(refName, this.beanName);
return bean;
}
}
catch (BeansException ex) {
throw new BeanCreationException(
this.beanDefinition.getResourceDescription(), this.beanName,
"Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex);
}
}对属性进行最终解析的是resolveValueIfNecessary方法，这个方法包含了所有注入类型的处理：
public Object resolveValueIfNecessary(Object argName, Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
//对RuntimeBeanReference进行解析，RuntimeBeanReference
// 是在对BeanDefinition进行解析时生成的数据对象
//对Bean Reference的解析
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);
}
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;
}
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);
}
//对ManagedArray进行解析
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);
}
//对ManagedList进行解析
else if (value instanceof ManagedList) {
// May need to resolve contained runtime references.
return resolveManagedList(argName, (List<?>) value);
}
//对ManagedSet进行解析
else if (value instanceof ManagedSet) {
// May need to resolve contained runtime references.
return resolveManagedSet(argName, (Set<?>) value);
}
//对ManagedMap进行解析
else if (value instanceof ManagedMap) {
// May need to resolve contained runtime references.
return resolveManagedMap(argName, (Map<?, ?>) value);
}
//对ManagedProperties进行解析
else if (value instanceof ManagedProperties) {
Properties original = (Properties) value;
Properties copy = new Properties();
for (Map.Entry<Object, Object> propEntry : original.entrySet()) {
Object propKey = propEntry.getKey();
Object propValue = propEntry.getValue();
if (propKey instanceof TypedStringValue) {
propKey = evaluate((TypedStringValue) propKey);
}
if (propValue instanceof TypedStringValue) {
propValue = evaluate((TypedStringValue) propValue);
}
copy.put(propKey, propValue);
}
return copy;
}
//对TypedStringValue进行解析
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 {
return evaluate(value);
}
}
//如：
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
try {
//从RuntimeBeanReference取得reference的名字，
// 这个RuntimeBeanReference是在载入BeanDefinition时根据配置生成
String refName = ref.getBeanName();
refName = String.valueOf(doEvaluate(refName));
//如果ref是在双亲IoC容器中，那就到双亲IoC容器中去获取
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");
}
return this.beanFactory.getParentBeanFactory().getBean(refName);
}
//在当前IoC容器中获取Bean，这里会触发一个getBean的过程，
// 如果依赖注入没有发生，这里会触发相应的依赖注入的发生
else {
Object bean = this.beanFactory.getBean(refName);
this.beanFactory.registerDependentBean(refName, this.beanName);
return bean;
}
}
catch (BeansException ex) {
throw new BeanCreationException(
this.beanDefinition.getResourceDescription(), this.beanName,
"Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex);
}
}在完成这个解析过程后，已经为依赖注入准备好了条件，这是真正把Bean对象设置到它所依赖的另一个Bean的属性中去的地方，其中处理的属性是各种各样的。依赖注入的发生是在BeanWrapper的setPropertyValues 中实现的，具体的完成却是在AbstractNestablePropertyAccessor中实现的，如代码所示：
public void setPropertyValues(PropertyValues pvs) throws BeansException {
setPropertyValues(pvs, false, false);
}
public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid)
throws BeansException {
List<PropertyAccessException> propertyAccessExceptions = null;
List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
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 LinkedList<PropertyAccessException>();
}
propertyAccessExceptions.add(ex);
}
}
// If we encountered individual exceptions, throw the composite exception.
if (propertyAccessExceptions != null) {
PropertyAccessException[] paeArray =
propertyAccessExceptions.toArray(new PropertyAccessException[propertyAccessExceptions.size()]);
throw new PropertyBatchUpdateException(paeArray);
}
}
public void setPropertyValue(PropertyValue pv) throws BeansException {
setPropertyValue(pv.getName(), pv.getValue());
}
public void setPropertyValue(String propertyName, Object value) throws BeansException {
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);
}
PropertyTokenHolder tokens = getPropertyNameTokens(getFinalPath(nestedPa, propertyName));
nestedPa.setPropertyValue(tokens, new PropertyValue(propertyName, value));
}
protected void setPropertyValue(PropertyTokenHolder tokens, PropertyValue pv) throws BeansException {
if (tokens.keys != null) {
processKeyedProperty(tokens, pv);
}
else {
processLocalProperty(tokens, pv);
}
}
private void processKeyedProperty(PropertyTokenHolder tokens, PropertyValue pv) {
//设置token的索引和keys,getPropertyValue取得Bean中对注入对象的引用Array set map并返回
Object propValue = getPropertyHoldingValue(tokens);
String lastKey = tokens.keys[tokens.keys.length - 1];
//这里对Array进行注入
if (propValue.getClass().isArray()) {
PropertyHandler ph = getLocalPropertyHandler(tokens.actualName);
Class<?> requiredType = propValue.getClass().getComponentType();
int arrayIndex = Integer.parseInt(lastKey);
Object oldValue = null;
try {
if (isExtractOldValueForEditor() && arrayIndex < Array.getLength(propValue)) {
oldValue = Array.get(propValue, arrayIndex);
}
Object convertedValue = convertIfNecessary(tokens.canonicalName, oldValue, pv.getValue(),
requiredType, ph.nested(tokens.keys.length));
int length = Array.getLength(propValue);
if (arrayIndex >= length && arrayIndex < this.autoGrowCollectionLimit) {
Class<?> componentType = propValue.getClass().getComponentType();
Object newArray = Array.newInstance(componentType, arrayIndex + 1);
System.arraycopy(propValue, 0, newArray, 0, length);
setPropertyValue(tokens.actualName, newArray);
propValue = getPropertyValue(tokens.actualName);
}
Array.set(propValue, arrayIndex, convertedValue);
}
catch (IndexOutOfBoundsException ex) {
throw new InvalidPropertyException(getRootClass(), this.nestedPath + tokens.canonicalName,
"Invalid array index in property path '" + tokens.canonicalName + "'", ex);
}
}
//这里对List进行注入
else if (propValue instanceof List) {
PropertyHandler ph = getPropertyHandler(tokens.actualName);
Class<?> requiredType = ph.getCollectionType(tokens.keys.length);
List<Object> list = (List<Object>) propValue;
int index = Integer.parseInt(lastKey);
Object oldValue = null;
if (isExtractOldValueForEditor() && index < list.size()) {
oldValue = list.get(index);
}
Object convertedValue = convertIfNecessary(tokens.canonicalName, oldValue, pv.getValue(),
requiredType, ph.nested(tokens.keys.length));
int size = list.size();
if (index >= size && index < this.autoGrowCollectionLimit) {
for (int i = size; i < index; i++) {
try {
list.add(null);
}
catch (NullPointerException ex) {
throw new InvalidPropertyException(getRootClass(), this.nestedPath + tokens.canonicalName,
"Cannot set element with index " + index + " in List of size " +
size + ", accessed using property path '" + tokens.canonicalName +
"': List does not support filling up gaps with null elements");
}
}
list.add(convertedValue);
}
else {
try {
list.set(index, convertedValue);
}
catch (IndexOutOfBoundsException ex) {
throw new InvalidPropertyException(getRootClass(), this.nestedPath + tokens.canonicalName,
"Invalid list index in property path '" + tokens.canonicalName + "'", ex);
}
}
}
//这里对Map进行注入
else if (propValue instanceof Map) {
PropertyHandler ph = getLocalPropertyHandler(tokens.actualName);
Class<?> mapKeyType = ph.getMapKeyType(tokens.keys.length);
Class<?> mapValueType = ph.getMapValueType(tokens.keys.length);
Map<Object, Object> map = (Map<Object, Object>) propValue;
// IMPORTANT: Do not pass full property name in here - property editors
// must not kick in for map keys but rather only for map values.
TypeDescriptor typeDescriptor = TypeDescriptor.valueOf(mapKeyType);
Object convertedMapKey = convertIfNecessary(null, null, lastKey, mapKeyType, typeDescriptor);
Object oldValue = null;
if (isExtractOldValueForEditor()) {
oldValue = map.get(convertedMapKey);
}
// Pass full property name and old value in here, since we want full
// conversion ability for map values.
Object convertedMapValue = convertIfNecessary(tokens.canonicalName, oldValue, pv.getValue(),
mapValueType, ph.nested(tokens.keys.length));
map.put(convertedMapKey, convertedMapValue);
}
else {
throw new InvalidPropertyException(getRootClass(), this.nestedPath + tokens.canonicalName,
"Property referenced in indexed property path '" + tokens.canonicalName +
"' is neither an array nor a List nor a Map; returned value was [" + propValue + "]");
}
}
private Object getPropertyHoldingValue(PropertyTokenHolder tokens) {
// Apply indexes and map keys: fetch value for all keys but the last one.
//设置token的索引和keys
PropertyTokenHolder getterTokens = new PropertyTokenHolder();
getterTokens.canonicalName = tokens.canonicalName;
getterTokens.actualName = tokens.actualName;
getterTokens.keys = new String[tokens.keys.length - 1];
System.arraycopy(tokens.keys, 0, getterTokens.keys, 0, tokens.keys.length - 1);
Object propValue;
//getPropertyValue取得Bean中对注入对象的引用Array set map
try {
propValue = getPropertyValue(getterTokens);
}
catch (NotReadablePropertyException ex) {
throw new NotWritablePropertyException(getRootClass(), this.nestedPath + tokens.canonicalName,
"Cannot access indexed value in property referenced " +
"in indexed property path '" + tokens.canonicalName + "'", ex);
}
if (propValue == null) {
// null map value case
if (isAutoGrowNestedPaths()) {
int lastKeyIndex = tokens.canonicalName.lastIndexOf('[');
getterTokens.canonicalName = tokens.canonicalName.substring(0, lastKeyIndex);
propValue = setDefaultValue(getterTokens);
}
else {
throw new NullValueInNestedPathException(getRootClass(), this.nestedPath + tokens.canonicalName,
"Cannot access indexed value in property referenced " +
"in indexed property path '" + tokens.canonicalName + "': returned null");
}
}
return propValue;
} 这样就完成于对各种Bean属性的依赖注入过程。
在Bean的创建和对象依赖注入的过程中，需要依据BeanDefinition中的信息来递归地完成依赖注入。从上面的几个递归过程中可以看到，这些递归都是以getBean为入口的。一个递归是在上下文体系中查找需要的Bean和创建Bean的递归调用，另一个递归是在依赖注入时，通过递归调用容器的getBean方法，得到当前Bean的依赖Bean ，同时也触发对依赖Bean的创建和注入。在对Bean的属性进行依赖注入时，解析的过程也是一个递归的过程。这样，根据依赖关系， 一层一层地完成Bean的创建和注入，直到最后完成当前Bean的创建。有了这个顶层Bean的创建和对它的属性依赖注入的完成，意味着和当前Bean相关的整个依赖链的注入也完成了。
在Bean创建和依赖注入完成以后，在IoC容器中建立起一系列依集依赖关系联系起来的Bean ，这个Bean 已经不是简单的Java对象了。该Bean系列以及Bean之间的依赖关系建立完成以后，通过IoC容器的相关接口方法，就可以非常方便地供上层应用使用了。
