@Override
	protected boolean canConvertFrom(Message<?> message, Class<?> targetClass) {
		return super.canConvertFrom(message, targetClass) && supportsPayloadType(message.getPayload().getClass());
	}
Subclasses implement this to specify supported payload types

@return an array of supported classes or null if any target type is supported
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/integration/bus/converter/AbstractFromMessageConverter.java