Spring源码学习IOC(7)：浅析aware相关接口_spring中awary相关接口-CSDN博客

本文解析了Spring框架中Aware接口的工作原理，介绍了BeanFactoryAware等接口如何在bean实例化过程中被Spring回调以注入资源。

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spring中有一大堆Aware结尾接口, 例如BeanFactoryAware, ApplicationContextAware, ServletContextAware等

在程序中我们自定义的bean实现了 Aware相关接口 spring 通过回调就可以获得一些资源

比如说我们的bean实现BeanFactoryAware spring会在bean实例化(getBean)阶段回调该setBeanFactory方法注入BeanFactory实例(也就是this)

spring BeanFactoryAware 接口定义

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 public interface BeanFactoryAware {  
   
    void setBeanFactory(BeanFactory beanFactory) throws BeansException;  
   
 }

spring容器中的bean 实例化是在AbstractBeanFactory getBean中发生

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 public Object getBean(String name, Class requiredType, Object[] args) throws BeansException {  
     return doGetBean(name, requiredType, args, false);  
 }  

调用的 doGetBean 方法比较复杂简单看看创建单例这段

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 protected Object doGetBean(  
             final String name, final Class requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {  
   
         final String beanName = transformedBeanName(name);  
             .................略          // Create bean instance.  
             //bean的定义是不是单例   
             if (mbd.isSingleton()) {  
                 sharedInstance = getSingleton(beanName, new ObjectFactory() {  
                     public Object getObject() throws BeansException {  
                         try {  
                             // 是一个抽象方法  在子类AbstractAutowireCapableBeanFactory中实现  
                             return createBean(beanName, mbd, args);  
                         }  
                         catch (BeansException ex) {  
                             destroySingleton(beanName);  
                             throw ex;  
                         }  
                     }  
                 });  
                 bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);  
             }  
   
         .................略  
         return bean;  
     }  

AbstractAutowireCapableBeanFactory createBean方法

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 protected Object createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)  
         throws BeanCreationException {  
   
     AccessControlContext acc = AccessController.getContext();  
     return AccessController.doPrivileged(new PrivilegedAction() {  
         public Object run() {  
             .................略  
             //关注doCreateBean方法  
             Object beanInstance = doCreateBean(beanName, mbd, args);  
             if (logger.isDebugEnabled()) {  
                 logger.debug("Finished creating instance of bean '" + beanName + "'");  
             }  
             return beanInstance;  
         }  
     }, acc);  
 }  

doCreateBean方法

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 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {  
         // Instantiate the bean.  
         BeanWrapper instanceWrapper = null;  
         if (mbd.isSingleton()) {  
             instanceWrapper = (BeanWrapper) this.factoryBeanInstanceCache.remove(beanName);  
         }  
         .................略  
         // Initialize the bean instance.  
         Object exposedObject = bean;  
         try {  
             populateBean(beanName, mbd, instanceWrapper);  
             //实现 *Aware部分接口， InitializingBean接口  方法调用在此发生  
             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);  
             }  
         }  
   
         .................略  
         return exposedObject;  
 }  

initializeBean方法

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 protected Object initializeBean(String beanName, Object bean, RootBeanDefinition mbd) {  
     if (bean instanceof BeanNameAware) {  
         ((BeanNameAware) bean).setBeanName(beanName);  
     }  
     if (bean instanceof BeanClassLoaderAware) {  
         ((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());  
     }  
     // 如果当前bean 是BeanFactoryAware的一个实例   
     if (bean instanceof BeanFactoryAware) {  
         //回调当前实例注入资源  
         ((BeanFactoryAware) bean).setBeanFactory(this);  
     }  
   
     Object wrappedBean = bean;  
     if (mbd == null || !mbd.isSynthetic()) {  
         //BeanPostProcessor 接口  postProcessBeforeInitialization方法回调  
         wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);  
     }  
     try {  
         // 实现InitializingBean接口  afterPropertiesSet方法调用  
         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;  
 }  

Spring aware相关接口