spring XXXAWARE

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

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

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

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

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

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

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