Javax WebSocket encoder/decoders not working in jetty 10.0.x

[lachlan-roberts]

Jetty version
10.0.x

Description
This example of a basic javax websocket string decoder which appends a = character to the end of each message, works in 9.4.x but not 10.0.x.

public static class MyStringDecoder extends StringDecoder
{
    @Override
    public String decode(String s)
    {
        return s + "=";
    }
}

@ServerEndpoint(value = "/", decoders = {MyStringDecoder.class})
public static class ConfiguredEchoSocket
{
    ...
}

The tests for encoders/decoders really only test the decoders themselves and don't seem to test them live in a websocket connection. Testing for this should be improved and the implementation in 10.0.x should be fixed to maintain the correct behaviour.