code: @Override
  	public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {
  		// accepts the beans in the order of classpath, which allow me to override beans
  		// easily
  		if (containsBean(beanName)) {
  			return;
  		}
  		// just continue normally
  		super.registerBeanDefinition(beanName, beanDefinition);
  	}
docs: /*
  (non-Javadoc)
  
  @see org.springframework.beans.factory.support.DefaultListableBeanFactory#
  registerBeanDefinition(java.lang.String,
  org.springframework.beans.factory.config.BeanDefinition)