JSON Java 8 LocalDateTime format in Spring Boot

Question

I'm having a small problem with formatting a Java 8 LocalDateTime in my Spring Boot Application. With 'normal' dates I have no problem, but the LocalDateTime fields are converted to the following:

"startDate" : {
    "year" : 2010,
    "month" : "JANUARY",
    "dayOfMonth" : 1,
    "dayOfWeek" : "FRIDAY",
    "dayOfYear" : 1,
    "monthValue" : 1,
    "hour" : 2,
    "minute" : 2,
    "second" : 0,
    "nano" : 0,
    "chronology" : {
      "id" : "ISO",
      "calendarType" : "iso8601"
    }
  }

While I would like convert it to something like:

"startDate": "2015-01-01"

My code looks like this:

@JsonFormat(pattern="yyyy-MM-dd")
@DateTimeFormat(iso = DateTimeFormat.ISO.TIME)
public LocalDateTime getStartDate() {
    return startDate;
}

But either of the above annotations don't work, the date keeps getting formatted like above. Suggestions welcome!

Answer 1

update: Spring Boot 2.x doesn't require this configuration anymore. I've written a more up to date answer here.

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(This is the way of doing it before Spring Boot 2.x, it might be useful for people working on an older version of Spring Boot)

I finally found here how to do it. To fix it, I needed another dependency:

compile("com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.4.0")

By including this dependency, Spring will automatically register a converter for it, as described here. After that, you need to add the following to application.properties:

spring.jackson.serialization.write_dates_as_timestamps=false

This will ensure that a correct converter is used, and dates will be printed in the format of 2016-03-16T13:56:39.492

Annotations are only needed in case you want to change the date format.