code: @Override
     	protected MultipartResolver lookupMultipartResolver() {
     		WebApplicationContext wac = (WebApplicationContext)RythmConfigurer.getInstance().getApplicationContext();
     		String beanName = getMultipartResolverBeanName();
     		if (wac != null && wac.containsBean(beanName)) {
     			if (logger.isDebugEnabled()) {
     				logger.debug("Using MultipartResolver '" + beanName + "' for MultipartFilter");
     			}
     			return wac.getBean(beanName, MultipartResolver.class);
     		} else {
     			return this.defaultMultipartResolver;
     		}
     	}
docs: Look for a MultipartResolver bean in the root web application context.
  Supports a "multipartResolverBeanName" filter init param; the default
  bean name is "filterMultipartResolver".
  <p>This can be overridden to use a custom MultipartResolver instance,
  for example if not using a Spring web application context.
  @return the MultipartResolver instance, or {@code null} if none found