spring-注册 DisposableBean

spring中不但提供了对于初始化方法的扩展入口，同样也提供了销毁方法的扩展入口，对 于销毁方法的扩展，除了我们熟知的配置属性 destroy-method方法外，用户还可以注册后处理 器DestructionAwareBeanPostProcessor来统一处理bean的销毁方法，代码如下：

protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
   AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);
   if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
      if (mbd.isSingleton()) {
         // Register a DisposableBean implementation that performs all destruction
         // work for the given bean: DestructionAwareBeanPostProcessors,
         // DisposableBean interface, custom destroy method.
         registerDisposableBean(beanName,
               new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
      }
      else {
         // A bean with a custom scope...
         Scope scope = this.scopes.get(mbd.getScope());
         if (scope == null) {
            throw new IllegalStateException("No Scope registered for scope name '" + mbd.getScope() + "'");
         }
         scope.registerDestructionCallback(beanName,
               new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
      }
   }
}