Hey Michael! "myFileBinder" in the spring.binders configuration file is simply the name of the custom binder we just created. It is particularly useful in cases where you have different binder implementations on the classpath and you must specify which binder will be used by default/which binder will be used for each and every Spring Cloud Stream input/output binding in your application.yml config file.

The message handling is masterfully managed by the Spring Cloud Stream abstraction that we do not necessarily need to know, but you can check this link to get and idea of how it works: https://github.com/spring-cloud/spring-cloud-stream/blob/55ae6b087d6b3bcfbbb8c929a68120a98b09869f/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractMessageChannelBinder.java. Since the code is fully open source you can easily verify the inner workings of Spring Cloud Stream's abstraction.