Spring Integration defines a top-level interface for the message channel that should be implemented by any of the concrete channel implementations, as shown here:

public interface MessageChannel {
  boolean send(Message<?> message);
  boolean send(Message<?> message, long timeout);
}

The MessageChannel interface defines two versions of the send method—one which accepts only Message as an argument while the other one accepts an additional parameter (timeout). The send method returns true if the message is sent out successfully; otherwise, if it times out or the sending fails for some reason, it returns false.

Further, Spring Integration provides a sub type of the MessageChannel interface to support two types of channels: PollableChannel and SubscribableChannel. This is explained in more detail in the following points: