Created attachment 30934 [details] TestEncodingDecoding.patch NPE is thrown when WS endpoint has associated encoder or decoder with type using generics. Example: Decoder.Text<List<String>> Here I attach patch of org.apache.tomcat.websocket.pojo.TestEncodingDecoding illustrating the case.
Thanks for the report and the test case. I have fixed this in 8.0.x for 8.0.0-RC6 onwards and in 7.0.x for 7.0.48 onwards.