(Since no-one replied) I don’t know / use KNIME and don’t use java to access CH but but since you’ve got a 401 error I suspect the issue is the user authentication isn’t being sent / fields are being sent incorrectly / http authentication header is not right. The link you posted above asks me for my KNIME login to read it so I haven’t.
I don’t see why using java would come into it - unless you’ve worked out that the java compiler and/or runtime version has a bug? In which case tell Oracle too.
The only other comms. issue I’ve come across is the certificate chain not matching those supplied by CH - but that should give you a different error.
(From a very cursory look at the KNIME docs):
Presumably to get the data you’re using the IO → File handling → Remote → Connections → Remote connection node to get the data (e.g. as in https://www.knime.org/files/node-documentation/org.knime.base.filehandling.remote.connectioninformation.node.https.HTTPSConnectionInformationNodeFactory.html)? If so, that seems to allow authentication, but it doesn’t go into exactly how it’s doing that so I’d check the http header that’s getting sent. It should be as per the API documentation e.g. the username CH supply and a blank password.
(You might even be able to get KNIME to report on this as it’s got a IO → File handling → Remote → URI → Extract URI info node).
It looks (from my 10 minute scan) as if KNIME should be capable of communicating with CH. It even looks like there’s a node for an Amazon S3 Connection so you may be able to download document images / additional financial data should you wish.
And finally - and apologies if you gave detailed info in your link above: http://testthewebforward.org/docs/bugs.html
Good luck.
Chris