Converting Javascript Date object to Java LocalDateTime

Question

I'm trying to get a UTC time from a Javascript front end to a Java backend. I wanted to accomplish this by using Date.toISOString() and sending that object to the Java backend. However, an issue I noticed is that toISOString() returns the timestamp in YYYY-MM-DDTHH:mm:ss.sssZ format, and this format does not match any of the Java 8 pre-defined LocalDateTime formatters.

My question is, is there a best practice to do what I'm trying to do? I'm aware I can write a custom Java formatter to match the Javascript output. However, I wondered if there was a standard way to accomplish this as it seems like a very common case.

LocalDateTime in which time zone? If server time zone, use LocalDateTime.ofInstant(Instant.parse(dateString), ZoneId.systemDefault()) --- Are you sure you want a local date/time? — Andreas
– Andreas, Commented Jun 10, 2020 at 16:53
LocalDateTime is the wrong class to use on the Java side. Your ISO string defines a point in time. LocalDateTime cannot represent that. Use Instant or ZonedDateTime. — Anonymous
– Anonymous, Commented Jun 10, 2020 at 17:32

sidgate · Accepted Answer · 2020-06-10 17:08:00Z

5

There are default ISO date formatters available. You can use following

LocalDateTime date = LocalDateTime.parse(str, DateTimeFormatter.ISO_DATE_TIME);

Note that this will assume the LocalDateTime of UTC timezone.

Update: as per Andreas' comment.

If you wish to get instance of LocalDateTime in server timezone, use

LocalDateTime.ofInstant(Instant.parse(str), ZoneId.systemDefault())

edited Jun 10, 2020 at 17:08

answered Jun 10, 2020 at 16:52

sidgate

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2 Comments

Andreas Over a year ago

That ignores the time zone, making the LocalDateTime be UTC in this case. How do you know OP wants the local date/time in UTC?

Jon Over a year ago

You are right, ISO_DATE_TIME does work! I was under the impression that it wouldn't because the examples provided on the Java docs were '2011-12-03T10:15:30', '2011-12-03T10:15:30+01:00' and '2011-12-03T10:15:30+01:00[Europe/Paris]'. I did not realize the Z was a valid zone it would detect.

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