@Override
        public RequestBody convert(T value) throws IOException {
            try {
                byte[] content;
                if (config.isJSONB()) {
                    content = JSONB.toBytes(
                            value,
                            config.getSymbolTable(),
                            config.getWriterFilters(),
                            config.getWriterFeatures()
                    );
                } else {
                    content = JSON.toJSONBytes(
                            value,
                            config.getDateFormat(),
                            config.getWriterFilters(),
                            config.getWriterFeatures()
                    );
                }
                return RequestBody.create(MEDIA_TYPE, content);
            } catch (Exception e) {
                throw new IOException("Could not write JSON: " + e.getMessage(), e);
            }
        }
Fastjson for Retrofit Converter Json Factory.

@author ligboy, wenshao
@author Victor.Zxy
@see Converter.Factory
@since 2.0.2
extension/src/main/java/com/alibaba/fastjson2/support/retrofit/Retrofit2ConverterFactory.java