A DESCRIPTION OF THE PROBLEM :
RFC 7231 states:
'A payload within a GET request message has no defined semantics;
   sending a payload body on a GET request might cause some existing
   implementations to reject the request.'

In other words whilst not prohibited, it is extremely unusual/unlikely for a GET request to have a request body. The vast majority of HTTP clients DO NOT include a `Content-Length: 0` header when making a GET request.

For example here is the verbose output of curl doing a GET request:

> GET / HTTP/1.1
> Host: oracle.com
> User-Agent: curl/7.77.0
> Accept: */*

Similarly the legacy HttpUrlConnection Java class does NOT add a Content-Length: 0 for GET requests.

For HTTP methods that are not expected to have a request body (GET/HEAD/OPTIONS/DELETE) adding a `Content-Length: 0` header MAY confuse the server. For example, see this bug in Oracle Helidon: https://github.com/oracle/helidon/issues/3988


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See test-case in this Oracle Helidon problem report: https://github.com/oracle/helidon/issues/3988

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
HttpClient WebSocket upgrade GET requests (particularly for WebSocket upgrade requests) should not include in a Content-Length: 0 header. It is redundant and may cause issues when present
ACTUAL -
HttpClient adds Content-Length: 0 to all requests without a request body. Calling code has no way to control/modify this behaviour.

CUSTOMER SUBMITTED WORKAROUND :
No workaround possible, prevents Oracle JDK HttpClient working with Oracle Helidon WebSocket applications.

FREQUENCY : always