Clean up the API by removing FIXConnection.getChannel()

[ddimtirov]

Removing getChannel() and introducing a second connection constructor with upstream and downstream pipe, allows us to get rid of virtually all generics and simplify the pipe code. It is also increases the encapsulation of the connection opening the possibility of alternative (non-channel based) transports for exotic scenarios, without affecting client code.

While the getChannel() may look like logical necessity, in practice it was not used in this codebase and I don't find usages in my codebase. If I wanted to get a handle of it, I could have gotten it at the place of constructing the connection.

[ddimtirov]

Added some comments in the interesting spots - most/all of the changes in the other files are removing generics and imports.

[ddimtirov]

@jvirtanen please and let me know if you approve of the idea - if yes, I'll fix the failing checks.

If no - please close :-)

[jvirtanen]

Hi @ddimtirov! Sorry, I missed this earlier in the week; I will have a look. 🔍

[jvirtanen]

Nice work, @ddimtirov! 🙌🏼

I feel that the challenges in adopting Philadelphia to work with other transports than SocketChannel strengthen how I'm feeling this library should ultimately work: just provide methods to parse and format complete FIX messages from and to various buffers, leaving the reading and writing of these buffers outside the scope of the library. This would also improve interoperability with libraries such as Aeron and Netty.

[ddimtirov]

Addressed all feedback, please have a look at the close() method - it looks weird, but it is compact and clean.

[jvirtanen]

Looking good, @ddimtirov! 🙌🏼 I just left a few more comments, and then, as last time, could you please squash the changes into a single commit? 🙂

[ddimtirov]

Done, the split commits (easier to review) are available in https://github.com/ddimtirov/philadelphia/tree/philadelphia-250-maintenance

[jvirtanen]

Thank you, @ddimtirov! 🚀

[ddimtirov]

@jvirtanen, what about a release? Is there anything that you would like done before that?

[jvirtanen]

@ddimtirov Yes! I've started some preparations for the 2.0.0 release. 👍🏼

[ddimtirov]

Let me know if you need any help (tests, measurements, doc drafts, etc.)