Issue #4548 - clean up websocket removing duplicated and unused classes

[lachlan-roberts]

Closes #4548

• Create new module websocket-util which contains implementation classes shared by websocket-jetty and websocket-javax.
• Many of these classes had to be changed as the javax and jetty versions of them differed slightly.

Other general cleanups, removed unused interfaces and classes, etc..

[joakime]

Quite the mess you have here. :-)

The InvokerUtils has 2 versions.

The javax version is the most complete and should be the one we settle on for websocket-core (or even jetty-util)
The ReflectUtil could probably be in jetty-util as well.

[joakime]

The MessageWriter should not use OutputStreamWriter, as the contract for OutputStreamWriter violates the rules of RFC6455 (we MUST validate outgoing UTF-8 and fail the connection if in violation. OutputStreamWriter will use replacement characters, which is not allowed)

[lachlan-roberts]

@joakime good catch, I see that this is a problem but it would also be good to not duplicate the implementations, and we probably want to use the ByteBufferPool instead of allocating CharBuffers.

I see that this is also going to be a problem with our MessageReader which I have not changed. It implements InputStreamReader and so will have the same problem with the replacement characters.

I might leave out the changes to MessageWriter, and put a separate issue up (#4538). I'm having enough trouble getting this PR working as is.

[lachlan-roberts]

I had to change InvokerUtils so that it gets passed in the MethodHandles.Lookup, this makes it have the same access permissions as the calling module and we don't get lots of IllegalAccessExceptions.

MessageWriter reverted, more work needed in new PR.

[lachlan-roberts]

Can I get some reviews on this soon. Any other work in jetty-10 websocket would likely cause lots of merge conflicts as there are so many files changed here.

I also have some further changes based off this branch to fix issues #4538 and #4571. So I can put PRs up for those once this has been merged.

[gregw]

There are aspects of these classes I don't like.... but in general the move to util is good!

[joakime]

There are aspects of these classes I don't like.... but in general the move to util is good!

Please file issues about what you don't like.