Unable to obtain OffsetDateTime from TemporalAcces

问题:

When I do this

String datum = "20130419233512";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmss").withZone(ZoneId.of("Europe/Berlin"));
OffsetDateTime datetime = OffsetDateTime.parse(datum, formatter);

I get the following exception:

    java.time.format.DateTimeParseException: Text '20130419233512' could not be parsed: 
Unable to obtain OffsetDateTime from TemporalAccessor: {InstantSeconds=1366407312},ISO,Europe/Berlin resolved 
to 2013-04-19T23:35:12 of type java.time.format.Parsed

How can I parse my datetime string so that it is interpreted as always being from the timezone "Europe/Berlin" ?

回答1:

The problem is that there is a difference between what a ZoneId is and a ZoneOffset is. To create a OffsetDateTime, you need an zone offset. But there is no one-to-one mapping between a ZoneId and a ZoneOffset because it actually depends on the current daylight saving time. For the same ZoneId like "Europe/Berlin", there is one offset for summer and a different offset for winter.

For this case, it would be easier to use a ZonedDateTime instead of an OffsetDateTime. During parsing, the ZonedDateTime will correctly be set to the "Europe/Berlin" zone id and the offset will also be set according to the daylight saving time in effect for the date to parse:

public static void main(String[] args) {
    String datum = "20130419233512";
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmss").withZone(ZoneId.of("Europe/Berlin"));
    ZonedDateTime datetime = ZonedDateTime.parse(datum, formatter);

    System.out.println(datetime.getZone()); // prints "Europe/Berlin"
    System.out.println(datetime.getOffset()); // prints "+02:00" (for this time of year)
}

Note that if you really want an OffsetDateTime, you can use ZonedDateTime.toOffsetDateTime() to convert a ZonedDateTime into an OffsetDateTime.

回答2:

There's no offset in your source data, and thus OffsetDateTime is not the correct type to use during parsing.

Instead, use a LocalDateTime, since that is the type that most closely resembles the data you have. Then use atZone to assign it a time zone, and if you still need an OffsetDateTime, you can call toOffsetDateTime from there.

String datum = "20130419233512";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
LocalDateTime datetime = LocalDateTime.parse(datum, formatter);
ZonedDateTime zoned = datetime.atZone(ZoneId.of("Europe/Berlin"));
OffsetDateTime result = zoned.toOffsetDateTime();