java.time.Duration 实现与 ISO8601 标准

Question

IIUC java.time 应该结束多个日期库和相关问题，并提供一些好的和标准化的东西。所以得知 java.time.Duration 违反了 iso8601 标准，我有点震惊。虽然应该可以解析:P2Y1DT1S，因为它按标准有效，java.time.Duration 最多只能解析几天(因此您必须通过 P731DT1S 和 java.time.Period 根本无法做到这一点，因为它不允许时间部分。

问题:

• 为什么？是否有正当理由不根据规范进行区间解析？我忽略了什么？

• 或者是否有一些现成的类可以解析 ISO8601？

Answer 1

嗯，解析这样一个字符串意味着它会产生一个对象，该对象支持同时出现这两个概念——一种 PeriodDuration。但是 Java 中没有，它的基本原理是 JodaStephen 的 explained here:

Note that a Duration contains an amount of seconds, not separate amounts of seconds, minutes and hours. The amount of seconds can exceed 24 hours, thus a Duration can represent a "day". But it is a fixed 24 hours day. By contrast, the representation of a "day in Period is descriptive and takes into account DST. The state of a Period is formed from three separate fields - days, months and years.

Bear in mind that "The customer occupied the hotel room for 2 days and seventeen and a half hours, P2DT17H30M" has the possibility to be complicated by DST cutovers. Using Period and Duration separately things are clear - Period is affected by DST cutovers and Duration is not.

^{(强调我的。)}

简而言之，这两个概念处理 DST 的方式不同，将两者结合起来会使事情变得复杂。

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关于你的第二个问题，this answer建议使用org.threeten.extra.PeriodDuration库提供的ThreeTen-Extra类。