HTTP Error 403 when using Apache WebClient on HTTPS Service (that does not have any certificates)

Question

The java application I'm working used to call an inhouse rest service via http which delivers a PDF file as a response. The rest service has now changed it's url and switched from http to https.

I have changed the java code of my application accordingly and am now getting a http error 403 (forbidden) when calling the service.

I use the Apache Webclient and I have only changed the url and the scheme in the source code.

I talked to to the service programmer and it turns out, that his service does not do any authorization or authentication. There is also no certificate tied to his service.

When testing the rest servcice call in Insomnia I had to disable all validation of certificates before the call would work.

My question is: How do I configure the Apache Webclient so that there is no validation of certificates. I suspect that this is what causes the error 403.

Any help would be much appreciated! :)

Ciao Lars

PS: Don't ask why the service changes to https but uses no secure techniques whatsoever.