The SSLSession.getPeerCertificateChain() method implementation has been removed

The javax.net.ssl.SSLSession.getPeerCertificateChain() method implementation was removed from the SunJSSE provider and HTTP client implementation in Java SE 15. The default implementation will now throw an UnsupportedOperationException. Applications using this method should be updated to use the javax.net.ssl.SSLSession.getPeerCertificates() method instead.

For more information on these changes, see Removed Features and Options in Java SE 15.