Jackson serialization of OffsetDateTime with DateTimeFormat.ISO.DATE_TIME ignores zero milliseconds

Question

I have a class that will get serialized into JSON with the following attribute:

  @JsonProperty("validTo")
  @org.springframework.format.annotation.DateTimeFormat(iso = org.springframework.format.annotation.DateTimeFormat.ISO.DATE_TIME)
  private OffsetDateTime validTo;

I'm also using the default spring-boot ObjectMapper with Jackson. This works fine if the validTo DateTime has non-zero mili/nanoseconds. However, if they are zero, the result will not include them at all.

Value OffsetDateTime.of(2000, 10, 10, 10, 10, 10, 1000000, ZoneOffset.UTC) would correctly translate to 2000-10-10T10:10:10.001Z

But OffsetDateTime.of(2000, 10, 10, 10, 10, 10, 0, ZoneOffset.UTC) would incorrectly translate to 2000-10-10T10:10:10Z

Why is that? The javadoc of the format used in the annotation describes it as The most common ISO Date Time Format yyyy-MM-dd'T'HH:mm:ss.SSSXXX — for example, "2000-10-31T01:30:00.000-05:00"., which appears to include the zeros.

Answer 1

It looks like Jackson ignores @DateTimeFormat annotation and the real serialization happens in com.fasterxml.jackson.datatype.jsr310.ser.OffsetDateTimeSerializer.

You can test it if you annotate the field like this (it won't affect the result):

@JsonProperty("creationDateTime")
@DateTimeFormat(pattern = "yyyy")
private OffsetDateTime validTo;