OffsetDateTime returns the datetime in wrong format - spring

Question

I use a Spring 4.3.4, a Jackson 2.8.6 and a Tomcat 8.5.11. I've some REST API:
#RestController
#RequestMapping(value = "/netadvice")
public class NetworkAdviceController {
...
#RequestMapping(
value = "/offsetDateTime",
method = RequestMethod.GET,
produces = MediaType.APPLICATION_JSON_VALUE)
public OffsetDateTime todayOffsetDateTime() {
return OffsetDateTime.now();
}
}
After call /netadvice/offsetDateTime I would like to receive the datetime in the following format: 2017-02-14T08:46:06.102Z but I receive something like this: 1487062454.957000000.
What did I wrong and how can I fix this issue?
The following code is my custom datetime serializer and deserializer:
#Configuration
public class JsonConfig {
public static final DateTimeFormatter FORMATTER = ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
#Bean
#Primary
public ObjectMapper objectMapper() {
ObjectMapper objectMapper = new ObjectMapper();
JavaTimeModule javaTimeModule = new JavaTimeModule();
javaTimeModule.addSerializer(OffsetDateTime.class, new OffsetDateTimeSerializer());
javaTimeModule.addDeserializer(OffsetDateTime.class, new OffsetdateTimeDeserializer());
objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
objectMapper.registerModule(javaTimeModule);
return objectMapper;
}
public class OffsetDateTimeSerializer extends JsonSerializer<OffsetDateTime> {
#Override
public void serialize(OffsetDateTime value, JsonGenerator gen, SerializerProvider serializers)
throws IOException {
gen.writeString(value.format(FORMATTER));
}
}
public class OffsetdateTimeDeserializer extends JsonDeserializer<OffsetDateTime> {
#Override
public OffsetDateTime deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
return OffsetDateTime.parse(p.getValueAsString(), FORMATTER);
}
}
}