Jackson serializes a ZonedDateTime wrongly in Spri

Question

I have a simple application with Spring Boot and Jetty. I have a simple controller returning an object which has a Java 8 ZonedDateTime:

public class Device {
  // ...
  private ZonedDateTime lastUpdated;

  public Device(String id, ZonedDateTime lastUpdated, int course, double latitude, double longitude) {
    // ...
    this.lastUpdated = lastUpdated;
    // ...
  }

  public ZonedDateTime getLastUpdated() {
    return lastUpdated;
  }
}

In my RestController I simply have:

@RequestMapping("/devices/")
public @ResponseBody List<Device> index() {
  List<Device> devices = new ArrayList<>();
  devices.add(new Device("321421521", ZonedDateTime.now(), 0, 39.89011333, 24.438176666));

  return devices;
}

I was expecting the ZonedDateTime to be formatted according to the ISO format, but instead I am getting a whole JSON dump of the class like this:

"lastUpdated":{"offset":{"totalSeconds":7200,"id":"+02:00","rules":{"fixedOffset":true,"transitionRules":[],"transitions":[]}},"zone":{"id":"Europe/Berlin","rules":{"fixedOffset":false,"transitionRules":[{"month":"MARCH","timeDefinition":"UTC","standardOffset":{"totalSeconds":3600,"id":"+01:00","rules":{"fixedOffset":true,"transitionRules":[],"transitions":[]}},"offsetBefore":{"totalSeconds":3600,"id":"+01:00","rules":{"fixedOffset":true,"transitionRules":[],"transitions":[]}},"offsetAfter":{"totalSeconds":7200,"id":"+02:00", ...

I just have a spring-boot-starter-web application, using spring-boot-starter-jetty and excluding spring-boot-starter-tomcat.

Why is Jackson behaving like this in Spring Boot?

** UPDATE **

For those looking for a full step by step guide how to solve this I found this after asking the question: http://lewandowski.io/2016/02/formatting-java-time-with-spring-boot-using-json/

Answer 1

There is a library jackson-datatype-jsr310. Try it.

This library covers new datetime API and includes serializers for ZonedDateTime too.

All you need is just to add JavaTimeModule:

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());

UPDATE

To convert datetime to ISO-8601 string you should disable WRITE_DATES_AS_TIMESTAMPS feature. You can easily do by either overriding ObjectMapper bean or by using application properties:

spring.jackson.serialization.WRITE_DATES_AS_TIMESTAMPS = false

Answer 2

The answer was already mentioned above but I think it's missing some info. For those looking to parse Java 8 timestamps in many forms (not just ZonedDateTime). You need a recent version of jackson-datatype-jsr310 in your POM and have the following module registered:

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule());
objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

To test this code

@Test
void testSeliarization() throws IOException {
    String expectedJson = "{\"parseDate\":\"2018-12-04T18:47:38.927Z\"}";
    MyPojo pojo = new MyPojo(ZonedDateTime.parse("2018-12-04T18:47:38.927Z"));

    // serialization
    assertThat(objectMapper.writeValueAsString(pojo)).isEqualTo(expectedJson);

    // deserialization
    assertThat(objectMapper.readValue(expectedJson, MyPojo.class)).isEqualTo(pojo);
}

Note that you can configure your object mapper globally in Spring or dropwizard to achieve this. I have not yet found a clean way to do this as an annotation on a field without registering a custom (de)serializer.

Answer 3

If you either don't rely on SpringBoot's auto-configuration feature - you don't provide spring.jackson.serialization.WRITE_DATES_AS_TIMESTAMPS = false property into your configuration file - or for whatever reason you create ObjectMapper instance manually. You can disable this feature programatically as follows:

ObjectMapper m = new ObjectMapper();
m.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);

this is for jackson 2.8.7