Jackson serializes a ZonedDateTime wrongly in Spring Boot

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