You could argue frameworks like Spring Integration or Apache Camel are FP outside + OO inside, but the key is that they allow side-effect channels for passing d

You could argue frameworks like Spring Integration or Apache Camel are FP outside + OO inside, but the key is that they allow side-effect channels for passing data ignoring the functional interconnections. Without that you would need to refactor the functional part every time any OO node wants to access any new data.