Java 8 ZonedDateTime

Question

I am trying to use ZonedDateTime.now(ZoneOffset.UTC).toString() to get the current time. It works well, but seems to cut off seconds / milliseconds when they are right on a rollover (00.000Z), or so it appears. Normally it wouldn't matter, but I am writing the data to ElasticSearch, which has a strict mapping for the date I am passing (acquired time).

I maybe am off in what I am thinking is happening, but want to try to make sure I can always provide a date/time with seconds and milliseconds.

Basic Code snippet (first pass was to add milliseconds, but appears seconds could also possibly be left out):

def utcDate = ZonedDateTime.now(ZoneOffset.UTC)
def utcDateStr = utcDate.toString()
utcDateStr = utcDateStr.contains(".") ? utcDateStr
        : utcDateStr.replace("Z","").concat(".000Z")

Want it to be in the format below, which it almost always is:

2016-06-16T05:43:07.624Z

Answer 1

Firstly, it sounds like you really want an Instant rather than a ZonedDateTime - that takes the time zone part out of the picture entirely. But either way, just use a DateTimeFormatter to format the value however you want.

It sounds like you want something like (in Java; adjust to Groovy appropriately):

DateTimeFormatter formatter = DateTimeFormatter
    .ofPattern("uuuu-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US)
    .withZone(ZoneOffset.UTC);
Instant now = Instant.now();
String text = formatter.format(now); 
System.out.println(text);

That will still output the milliseconds value even if it's 0.

(If you really want to use ZonedDateTime , you can do so with the same formatter. But conceptually, what I think you're trying to represent is just an instant in time, and Instant is the better fit for that.)

Answer 2

If you want to go the formatter route, you can build one like so:

DateTimeFormatter ES_ISO8601_FORMATTER = new DateTimeFormatterBuilder()
            .parseCaseInsensitive()
            .append(
                    new DateTimeFormatterBuilder()
                            .parseCaseInsensitive()
                            .append(ISO_LOCAL_DATE)
                            .appendLiteral('T')
                            .append(
                                    new DateTimeFormatterBuilder()
                                            .appendValue(HOUR_OF_DAY, 2)
                                            .appendLiteral(':')
                                            .appendValue(MINUTE_OF_HOUR, 2)
                                            .appendLiteral(':')
                                            .appendValue(SECOND_OF_MINUTE, 2)
                                            .appendFraction(NANO_OF_SECOND, 3, 9, true)
                                            .toFormatter()
                            )
                            .toFormatter()
            )
            .appendOffsetId()
            .toFormatter();

(That's cobbled together from the code in the DateTimeFormatter class in Java 8)

The change is basically giving

                                        .appendFraction(NANO_OF_SECOND, 3, 9, true)

a min width of 3, instead of 0 in the original ISO formatter