introduction
Spring provides the interface to a variety of Aware, facilitate access to the current operating environment from the context, the more common of several sub-interfaces: BeanFactoryAware, BeanNameAware, ApplicationContextAware, EnvironmentAware, BeanClassLoaderAware etc. Aware of the role of these can be learned from naming
Aware
deal with
Wherein BeanNameAware
, BeanClassLoaderAware
and BeanFactoryAware
three bean directly before the initialization process of the specific code in AbstractAutowireCapableBeanFactory.initializeBean
the method:
protected Object initializeBean(String beanName, Object bean, RootBeanDefinition mbd) {
// 判断对象实现的接口类型,处理特定的三种接口类型:BeanNameAware、BeanClassLoaderAware和BeanFactoryAware。
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(this);
}
// 开始Bean初始化前处理、初始化、初始化后处理
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
In addition to implementing those Aware of these three interfaces other than just not the same, they are using the BeanPostProcessor
interface to complete, and on BeanPostProcessor
the principle of the interface can this article: the BeanPostProcessor extension points of the Spring
As ApplicationContextAware
is the use of ApplicationContextAwareProcessor
implementation:
public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
AccessControlContext acc = null;
if (System.getSecurityManager() != null &&
(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}
if (acc != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
//具体实现
invokeAwareInterfaces(bean);
return null;
}, acc);
}
else {
//具体实现
invokeAwareInterfaces(bean);
}
return bean;
}
private void invokeAwareInterfaces(Object bean) {
if (bean instanceof Aware) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
}
The ApplicationContextAwareProcessor
registration mystery AbstractApplicationContext.prepareBeanFactory
method:
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this));
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);