jbx jbx - 3 months ago 66
JSON Question

Jackson serializes a ZonedDateTime wrongly in Spring Boot

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

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
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