public static ObjectMapper newDefaultObjectMapper() {
        final ObjectMapper mapper = provider.newObjectMapper();
        if (mapper == null) {
            throw new NullPointerException(
                    provider.getClass().getSimpleName() + ".newObjectMapper() returned null");
        }
        return mapper;
    }
Returns a newly-created {@link ObjectMapper} that is created by
either a {@link JacksonObjectMapperProvider} loaded via SPI or
the {@link DefaultJacksonObjectMapperProvider} if not specified.
core/src/main/java/com/linecorp/armeria/internal/common/JacksonUtil.java