Java 8 - ZonedDateTime 的 DateTimeFormatter 和 ISO_INSTANT 问题

Java 8 - DateTimeFormatter and ISO_INSTANT issues with ZonedDateTime

提问by asieira

So I would expect this code to work under the new Java 8 date/time package since all it does is to convert a given ZonedDateTime to string and back using the same built-in DateTimeFormatter instance (ISO_INSTANT):

所以我希望这段代码可以在新的 Java 8 日期/时间包下工作，因为它所做的只是使用相同的内置 DateTimeFormatter 实例 (ISO_INSTANT) 将给定的 ZonedDateTime 转换为字符串并返回：

ZonedDateTime now = ZonedDateTime.now();
System.out.println(ZonedDateTime.parse(
    now.format(DateTimeFormatter.ISO_INSTANT),
    DateTimeFormatter.ISO_INSTANT));

But apparently it doesn't:

但显然它没有：

Exception in thread "main" java.time.format.DateTimeParseException: Text '2014-09-01T19:37:48.549Z' could not be parsed: Unable to obtain ZonedDateTime from TemporalAccessor: {MilliOfSecond=549, NanoOfSecond=549000000, MicroOfSecond=549000, InstantSeconds=1409600268},ISO of type java.time.format.Parsed
    at java.time.format.DateTimeFormatter.createError(DateTimeFormatter.java:1918)
    at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1853)
    at java.time.ZonedDateTime.parse(ZonedDateTime.java:597)

I have seen this entry already, but it didn't help me because a need a ZonedDateTime object and not a local one and also because I already have 8u20 installed: Unable to obtain ZonedDateTime from TemporalAccessor using DateTimeFormatter and ZonedDateTime in Java 8

我已经看过这个条目，但它对我没有帮助，因为需要一个 ZonedDateTime 对象而不是本地对象，还因为我已经安装了 8u20：无法使用 Java 8 中的 DateTimeFormatter 和 ZonedDateTime 从 TemporalAccessor 获取 ZonedDateTime

Anyone have any idea what's happening here?

有人知道这里发生了什么吗？

采纳答案by JodaStephen

The ISO_INSTANTformatter is documented here- "This is a special case formatter intended to allow a human readable form of an Instant". As such, this formatter is intended for use with an Instantnot a ZonedDateTime.

该ISO_INSTANT格式是记录在这里- “这是格式化旨在允许即时的人类可读形式的特殊情况”。因此，此格式化程序旨在与Instantnot a 一起使用ZonedDateTime。

Formatting

格式化

When formatting, ISO_INSTANTcan format any temporal object that can provide ChronoField.INSTANT_SECONDSand ChronoField.NANO_OF_SECOND. Both Instantand ZonedDateTimecan provide these two fields, thus both work:

格式化时，ISO_INSTANT可以格式化任何可以提供ChronoField.INSTANT_SECONDS和的时态对象ChronoField.NANO_OF_SECOND。双方Instant并ZonedDateTime能提供这两个领域，因此这两种工作方式：

// works with Instant
Instant instant = Instant.now();
System.out.println(DateTimeFormatter.ISO_INSTANT.format(instant));

// works with ZonedDateTime 
ZonedDateTime zdt = ZonedDateTime.now();
System.out.println(zdt.format(DateTimeFormatter.ISO_INSTANT));

// example output
2014-09-02T08:05:23.653Z

Parsing

解析

When parsing, ISO_INSTANTwill only produce ChronoField.INSTANT_SECONDSand ChronoField.NANO_OF_SECOND. An Instantcan be built from those two fields, but ZonedDateTimerequires a ZoneIdas well:

解析时，ISO_INSTANT只会产生ChronoField.INSTANT_SECONDS和ChronoField.NANO_OF_SECOND。AnInstant可以从这两个字段构建，但也ZonedDateTime需要一个ZoneId：

To parse a ZonedDateTimeit is essential that a time-zone ZoneIdis present. The time-zone can be (a) parsed from the string, or (b) specified to the formatter (using JDK 8u20):

要解析 aZonedDateTime必须存在时区ZoneId。时区可以 (a) 从字符串中解析，或 (b) 指定给格式化程序（使用 JDK 8u20）：

// option a - parsed from the string
DateTimeFormatter f = DateTimeFormatter.ISO_DATE_TIME;
ZonedDateTime zdt = ZonedDateTime.parse("2014-09-02T08:05:23.653Z", f);

// option b - specified in the formatter - REQUIRES JDK 8u20 !!!
DateTimeFormatter f = DateTimeFormatter.ISO_INSTANT.withZone(ZoneId.systemDefault());
ZonedDateTime zdt = ZonedDateTime.parse("2014-09-02T08:05:23.653Z", f);

See documentation for ISO_ZONED_DATE_TIME, ISO_OFFSET_DATE_TIMEand ISO_DATE_TIME(any of these three can be used to parse a ZonedDateTimewithout specifying withZone()).

请参阅ISO_ZONED_DATE_TIME,ISO_OFFSET_DATE_TIME和ISO_DATE_TIME（这三个中的任何一个都可用于解析 aZonedDateTime而不指定withZone()）的文档。

Summary

概括

The ISO_INSTANTformatter is a special case formatter designed to work with Instant. If you are using a ZonedDateTimeyou should use a different formatter, such as ISO_DATE_TIMEor ISO_ZONED_DATE_TIME.

该ISO_INSTANT格式是一种特殊情况下格式化旨在与工作Instant。如果您使用的是ZonedDateTime，则应使用不同的格式化程序，例如ISO_DATE_TIME或ISO_ZONED_DATE_TIME。

回答by Cristina

I'm not sure, but this might be a bug in Java 8. Maybe it was intended to behave in this way, but I think that the workaround I'm going to propose to you should be the default behavior (when no ZoneId is specified, just take system default):

我不确定，但这可能是 Java 8 中的一个错误。也许它本打算以这种方式行事，但我认为我要向您提出的解决方法应该是默认行为（当没有 ZoneId 时）指定，只需采用系统默认值）：

ZonedDateTime now = ZonedDateTime.now();
DateTimeFormatter formatter = DateTimeFormatter.ISO_INSTANT
    .withZone(ZoneId.systemDefault());
System.out
    .println(ZonedDateTime.parse(now.format(formatter), formatter));

There's a similar bug which was fixed in OpenJDK: JDK-8033662- but it's only similar, not exactly the same.

OpenJDK 中修复了一个类似的错误：JDK-8033662- 但它只是相似，不完全相同。

回答by assylias

I don't know if it is the expected behaviour or not (it probably is) but technically the ISO_INSTANTformatter does not include a time zone. If you try with a DateTimeFormatter.ISO_ZONED_DATE_TIMEformatter instead you will get what you expect.

我不知道这是否是预期的行为（可能是），但从技术上讲，ISO_INSTANT格式化程序不包含时区。如果您尝试使用DateTimeFormatter.ISO_ZONED_DATE_TIME格式化程序，您将得到您所期望的。

回答by Morgan Koh

If you're using org.threeten.bpfrom Java 1.8, here's a Cheat Sheeton dealing with String to Date and vice versa.

如果您org.threeten.bp从Java 1.8开始使用，这里有一个关于处理字符串到日期的备忘单，反之亦然。

Date to String

日期到字符串

val date = Date()
val calendar = Calendar.getInstance().apply { time = date }
val zonedDateTime = DateTimeUtils.toZonedDateTime(calendar)
val formattedDate = DateTimeFormatter.ISO_INSTANT.format(zonedDateTime)

String to Date

字符串到日期

val dateString = "2020-03-04T09:04:43.835Z"
val dateInstant = Instant.from(DateTimeFormatter.ISO_INSTANT.parse(dateString))
DateTimeUtils.toDate(dateInstant)