Agfdhyk

A fragment from doc

A Message Endpoint represents the "filter" of a pipes-and-filters
architecture. As mentioned earlier, the endpoint’s primary role is to
connect application code to the messaging framework and to do so in a
non-invasive manner. In other words, the application code should
ideally have no awareness of the message objects or the message
channels.

Transformers, Filters, Service Activators are all Message Endpoints.
What I don't understand is why they are called so as an application actually can send messages into input channels and these "endpoints" are used in the middle of the chain. In other words, the app is aware about a channel, and not about endpoints.
Example:

@SpringBootApplication

@IntegrationComponentScan

public class SendToInputChannel {



    @Bean

        public IntegrationFlow flow() {

            return IntegrationFlows.from("input")

                .handle(System.out::println).get();

        }



    public static void main(String args) throws IOException {

        ConfigurableApplicationContext ctx = SpringApplication.run(SendToInputChannel.class, args);



        MessageChannel inputChannel = ctx.getBean("input", MessageChannel.class);

        for (int i = 0; i < 10; i++) {

            inputChannel.send(MessageBuilder.withPayload(i)

                .build());

        }



        ctx.close();



    }



}

Ekaterina, It all started from the Enterprise Integration Patterns (EIP) book and Spring Integration (SI) is effectively a Reference Implementation of the EIP. We were trying to stay pretty close to "that script". So as you can see from this excerpt - Message Endpoint is used to connect an application to a messaging channels. In other words SI in itself is a messaging framework since it provides internal channels to which various Filters/Endpoints could be connected.
Keep in mind that MessageChannel is an interface and could represent not only the internal channels implemented in SI. For example one can implement a MessageChannel interface that provides some proxy to a JMS queue or anything else, while Filters/Endpoints will remain the same/unchanged.

I can go on, but I hope that is enough for now, but fee free to follow up.