Issue
For some reason on the Serverside the content-length is 0 even though this Header was send and recieved.
By adding connection.setChunkedStreamingMode(); when sending a POST solved the issue, however I stil don't know why it's not working with the content-length Header.
Solution
In case anyone wants to know why Setting "connection.setChunkedStreamingMode()" did the trick.
The Client could send a request using http 1.0 or 1.1 but http 1.1 requests don't work with the content-length header added to it (which was added someware in the process). On the contrary the chunked mode does work for http 1.0 as well.
I tested this after I found this post from Clement Amarnath How do i send a POST request without Transfer Encoding:chunked from Jersey ReST Client 2.22.2
Answered By - MADforFUNandHappy
Answer Checked By - Mary Flores (JavaFixing Volunteer)