@Nullable
default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
postProcessAfterInitialization
@Nullable
default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
return bean;
}
InstantiationAwareBeanPostProcessor
BeanPostProcessor的子接口，它添加了实例化前回调，以及实例化后但在设置显式属性或自动装配之前的回调。
public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {
}
postProcessBeforeInstantiation
//在目标 bean 被实例化之前回调该方法
//返回的 bean 对象可能是一个代理来代替目标 bean，有效地抑制目标 bean 的默认实例化。
@Nullable
default Object postProcessBeforeInstantiation(Class beanClass, String beanName) throws BeansException {
return null;
}
postProcessAfterInstantiation
//在bean被实例化(通过构造函数或工厂方法)之后，但在Spring属性填充（来自显式属性或自动装配）发生之前,回调该方法
//这是在 Spring 的自动装配开始之前对给定 bean 实例执行自定义字段注入的理想回调。
//返回true，表示应该在bean上设置属性，该接口的正常实现类应该返回true
//返回false，表示应该跳过属性填充。
//返回false还将阻止在此bean实例上调用任何后续InstantiationAwareBeanPostProcessor 实例。
default boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
return true;
}
postProcessProperties
@Nullable
default PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName)
throws BeansException {
return null;
}
postProcessPropertyValues
@Deprecated
@Nullable
default PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {
return pvs;
}
SmartInstantiationAwareBeanPostProcessor
public interface SmartInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessor {}
predictBeanType
//预测最终从该处理器的 {@link #postProcessBeforeInstantiation} 回调返回的 bean 的类型
@Nullable
default Class predictBeanType(Class beanClass, String beanName) throws BeansException {
return null;
}
determineCandidateConstructors
//确定用于给定 bean 的候选构造函数
@Nullable
default Constructor[] determineCandidateConstructors(Class beanClass, String beanName)
throws BeansException {
return null;
}
getEarlyBeanReference
//获取对指定 bean 的早期访问的引用，通常用于解析循环引用。
//回调方法使post-processors有机会尽早暴露包装器 - 即在目标 bean 实例完全初始化之前。
//暴露的对象应该等同于 {@link #postProcessBeforeInitialization} / {@link #postProcessAfterInitialization} 否则会暴露的对象。
//请注意，此方法返回的对象将用作 bean 引用，除非post-processor从所述后处理回调返回不同的包装器。
default Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {
return bean;
}
CommonAnnotationBeanPostProcessor
postProcessProperties
@Override
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
Injectionmetadata metadata = findResourcemetadata(beanName, bean.getClass(), pvs);
try {
metadata.inject(bean, beanName, pvs);
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of resource dependencies failed", ex);
}
return pvs;
}
postProcessPropertyValues
@Deprecated
@Override
public PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) {
return postProcessProperties(pvs, bean, beanName);
}
AutowiredAnnotationBeanPostProcessor
postProcessProperties
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
Injectionmetadata metadata = findAutowiringmetadata(beanName, bean.getClass(), pvs);
try {
metadata.inject(bean, beanName, pvs);
}
catch (BeanCreationException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex);
}
return pvs;
}
postProcessPropertyValues
@Deprecated
@Override
public PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) {
return postProcessProperties(pvs, bean, beanName);
}
AbstractAutoProxyCreator
SmartInstantiationAwareBeanPostProcessor接口继承自InstantiationAwareBeanPostProcessor接口。
因此AbstractAutoProxyCreator一般是通过InstantiationAwareBeanPostProcessor接口的postProcessBeforeInstantiation方法和postProcessBeforeInstantiation方法来返回代理对象；
postProcessBeforeInstantiation阶段：前置处理器一般返回null，除非有TargetSource，就是对象已经创建了，则直接返回改beanpostProcessAfterInitialization阶段：如果在postProcessBeforeInstantiation阶段返回null，则待对象创建并初始化完成，再通过postProcessAfterInitialization方法使用动态代理根据实例对象创建增强的动态代理对象。
public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {
}
postProcessBeforeInstantiation
public Object postProcessBeforeInstantiation(Class beanClass, String beanName) {
Object cacheKey = getCacheKey(beanClass, beanName);
if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
if (this.advisedBeans.containsKey(cacheKey)) {
return null;
}
if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return null;
}
}
// Create proxy here if we have a custom TargetSource.
// Suppresses unnecessary default instantiation of the target bean:
// The TargetSource will handle target instances in a custom fashion.
// 如果我们有一个自定义的TargetSource，则在这里创建代理
TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
if (targetSource != null) {
if (StringUtils.hasLength(beanName)) {
this.targetSourcedBeans.add(beanName);
}
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
// 创建动态代理对象
Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
return null;
}
postProcessAfterInstantiation
public boolean postProcessAfterInstantiation(Object bean, String beanName) {
return true;
}
getEarlyBeanReference
//获取提前暴露出来的bean的引用
public Object getEarlyBeanReference(Object bean, String beanName) {
//生成该bean对应的cacheKey
Object cacheKey = this.getCacheKey(bean.getClass(), beanName);
//将该bean放入到earlyProxyReferences中用于表示该Bean执行过AOP
this.earlyProxyReferences.put(cacheKey, bean);
//如果需要的话，对给定的bean进行封装，例如，该bean需要被代理
return this.wrapIfNecessary(bean, beanName, cacheKey);
}
postProcessAfterInitialization
//Create a proxy with the configured interceptors if the bean is identified as one to proxy by the subclass.
//如果 bean 被子类标识为代理，则使用配置的拦截器创建一个代理。
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
if (bean != null) {
Object cacheKey = this.getCacheKey(bean.getClass(), beanName);
//如果该bean未执行过AOP，则进行封装，如果执行过，则不再进行封装
if (this.earlyProxyReferences.remove(cacheKey) != bean) {
return this.wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}
wrapIfNecessary
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// Create proxy if we have advice.
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
this.advisedBeans.put(cacheKey, Boolean.TRUE);
Object proxy = createProxy(
bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
