在调用AbstractAutowireCapableBeanFactory.populateBean方法，往当前bean中注册属性的时候，有如下代码：
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;
}
}
}
}
复制代码**==AutoWireAnnotationBeanPostProcessor==**就是其中的一个； 具体实现的功能，就是往当前的bean中注入@AutoWire标注的属性
@Nullable
public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable String beanName,
@Nullable Set autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {
InjectionPoint previousInjectionPoint = ConstructorResolver.setCurrentInjectionPoint(descriptor);
try {
Object shortcut = descriptor.resolveShortcut(this);
if (shortcut != null) {
return shortcut;
}
//对@Value的属性，做注入
Class type = descriptor.getDependencyType();
Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
if (value != null) {
if (value instanceof String) {
String strVal = resolveEmbeddedValue((String) value);
BeanDefinition bd = (beanName != null && containsBean(beanName) ? getMergedBeanDefinition(beanName) : null);
value = evaluateBeanDefinitionString(strVal, bd);
}
TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
return (descriptor.getField() != null ?
converter.convertIfNecessary(value, type, descriptor.getField()) :
converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));
}
//对数组、容器类型的处理
//因为是数组或容器，Sprng可以直接把符合类型的bean都注入到数组或容器中，处理逻辑是：
//1.确定容器或数组的组件类型
//2.调用findAutowireCandidates方法，获取与组件类型匹配的Map(beanName -> bean实例)
//3.将符合beanNames添加到autowiredBeanNames中
//在调用findAutowireCandidates的时候,addCandidateEntry中如果是MultiElementDescriptor || containsSingleton 调用descriptor.resolveCandidate 将bean注入返回值中
Object multipleBeans = resolveMultipleBeans(descriptor, beanName, autowiredBeanNames, typeConverter);
if (multipleBeans != null) {
return multipleBeans;
}
Map matchingBeans = findAutowireCandidates(beanName, type, descriptor);
if (matchingBeans.isEmpty()) {
if (isRequired(descriptor)) {
raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
}
return null;
}
String autowiredBeanName;
Object instanceCandidate;
//如果发现同一个属性有多个bean,使用@primary或者@Priority决定使用哪个
if (matchingBeans.size() > 1) {
autowiredBeanName = determineAutowireCandidate(matchingBeans, descriptor);
if (autowiredBeanName == null) {
if (isRequired(descriptor) || !indicatesMultipleBeans(type)) {
return descriptor.resolveNotUnique(type, matchingBeans);
}
else {
// In case of an optional Collection/Map, silently ignore a non-unique case:
// possibly it was meant to be an empty collection of multiple regular beans
// (before 4.3 in particular when we didn't even look for collection beans).
return null;
}
}
instanceCandidate = matchingBeans.get(autowiredBeanName);
}
else {
// We have exactly one match.
Map.Entry entry = matchingBeans.entrySet().iterator().next();
autowiredBeanName = entry.getKey();
instanceCandidate = entry.getValue();
}
if (autowiredBeanNames != null) {
autowiredBeanNames.add(autowiredBeanName);
}
return (instanceCandidate instanceof Class ?
descriptor.resolveCandidate(autowiredBeanName, type, this) : instanceCandidate);
}
finally {
ConstructorResolver.setCurrentInjectionPoint(previousInjectionPoint);
}
}
复制代码 - resolveMultipleBeans 提供了 @Auwired 一个容器类（List之类的）支持
- determineAutowireCandidate 解决了，同一个属性找到多个对应的bean时，如何获取唯一的那个bean
/**
* Find bean instances that match the required type.
* Called during autowiring for the specified bean.
* @param beanName the name of the bean that is about to be wired
* @param requiredType the actual type of bean to look for
* (may be an array component type or collection element type)
* @param descriptor the descriptor of the dependency to resolve
* @return a Map of candidate names and candidate instances that match
* the required type (never {@code null})
* @throws BeansException in case of errors
* @see #autowireByType
* @see #autowireConstructor
*/
protected Map findAutowireCandidates(
@Nullable String beanName, Class requiredType, DependencyDescriptor descriptor) {
String[] candidateNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
this, requiredType, true, descriptor.isEager());
Map result = new LinkedHashMap<>(candidateNames.length);
//如果已经解析过了直接装载进去
for (Class autowiringType : this.resolvableDependencies.keySet()) {
if (autowiringType.isAssignableFrom(requiredType)) {
Object autowiringValue = this.resolvableDependencies.get(autowiringType);
//key值是我们需要的类型，但value值未必。
//value可能是ObjectFactory，就得调用它的 getObject() 来获取真正的bean.
autowiringValue = AutowireUtils.resolveAutowiringValue(autowiringValue, requiredType);
if (requiredType.isInstance(autowiringValue)) {
result.put(ObjectUtils.identityToString(autowiringValue), autowiringValue);
break;
}
}
}
//如果不是自己依赖自己 ， 并且符合装配候选，就塞入result。
//何为符合装配候选（isAutowireCandidate）呢？稍后我们再详细分析。
for (String candidate : candidateNames) {
if (!isSelfReference(beanName, candidate) && isAutowireCandidate(candidate, descriptor)) {
addCandidateEntry(result, candidate, descriptor, requiredType);
}
}
if (result.isEmpty() && !indicatesMultipleBeans(requiredType)) {
// Consider fallback matches if the first pass failed to find anything...
DependencyDescriptor fallbackDescriptor = descriptor.forFallbackMatch();
for (String candidate : candidateNames) {
if (!isSelfReference(beanName, candidate) && isAutowireCandidate(candidate, fallbackDescriptor)) {
addCandidateEntry(result, candidate, descriptor, requiredType);
}
}
if (result.isEmpty()) {
// Consider self references as a final pass...
// but in the case of a dependency collection, not the very same bean itself.
for (String candidate : candidateNames) {
if (isSelfReference(beanName, candidate) &&
(!(descriptor instanceof MultiElementDescriptor) || !beanName.equals(candidate)) &&
isAutowireCandidate(candidate, fallbackDescriptor)) {
addCandidateEntry(result, candidate, descriptor, requiredType);
}
}
}
}
return result;
}
复制代码 ==本文内容，相当于populate中的 autoWireByType==