For the postback urls as its mentioned in documentation, need to have https and hence requires a ssl certificate to be installed in servers. Is it possible to have installed self signed certificates for postback to work. Because it will show error when that url is entered in browser, so just wanted to confirm back whether it works for postback's of order execution status.
Also if it works, does any such configuration needed to be done as part of the java client.
You can use Self signed certificate.
For java client you can download jar and use from this link https://github.com/rainmattertech/javakiteconnect/tree/master/dist or include maven depency.