为什么不正确地将字符串转换为日期?

问题描述

在我的Kotlin代码中:

In my Kotlin code:

   const val TS_DATE_PATTERN = "yyyy-MM-dd'T'HH:mm:ss.SSS"
   val ts = responseJsonObject.get("TS").getAsString()
   val tsDate = SimpleDateFormat(TS_DATE_PATTERN).parse(ts)
   val tsDateAsString = SimpleDateFormat(TS_DATE_PATTERN).format(tsDate)
   logger.info("ts = " + ts + " -> tsDate = " + tsDate + " -> tsDateAsString = " + tsDateAsString)

这是(为便于阅读而格式化)结果:

And here the (formatted for readability) result:

ts             = 2019-01-14T22:56:30.429582
tsDate         = Mon Jan 14 23:03:39 EET 2019
tsDateAsString = 2019-01-14T23:03:39.582

您可以看到 ts 和 tsDateAsString 的时间不同，尽管它们来自同一起点.

As you can see the ts and tsDateAsString have different times, although they came from the same starting point.

例如ts = 22:56:30，但在tsDateAsString = 23:03:39

为什么?

推荐答案

建议:尽可能使用 java.time -实用程序.

As a suggestion: whenever you can, use java.time-utilities.

SimpleDateFormat 具有毫秒级的特殊处理. S解析的所有内容均以毫秒为单位.只要处理3位数毫秒，一切都很好(您甚至可以使用一个S(即.S)毫秒来解析它们)，但是如果您使用6位数毫秒作为输入，您还将获得一个6位数的毫秒值(！).

SimpleDateFormat has a special handling for the milliseconds. Everything that is parsed by the S is treated as milliseconds. As long as you deal with 3-digit-milliseconds, everything is fine (you may even just use a single S (i.e. .S) for the milliseconds to parse them), but if you use 6-digit-milliseconds as input then you also get a 6-digit-millisecond(!)-value.

那么6位数毫秒实际上是3位数秒+ 3位数毫秒.那就是偏差的来源.

The 6-digit-milliseconds then are actually 3-digit seconds + the 3-digit milliseconds. That is where the deviation is coming from.

如何解决?好吧，要么缩短输入时间字符串并失去一些精度，要么使用首选的 DateTimeFormatter 而是使用与您的输入匹配的模式，即yyyy-MM-dd'T'HH:mm:ss.SSSSSS:

How to solve that? Well either shorten the input time string and lose some precision or use the preferred DateTimeFormatter instead with a pattern matching your input, i.e. yyyy-MM-dd'T'HH:mm:ss.SSSSSS:

val TS_DATE_PATTERN = "yyyy-MM-dd'T'HH:mm:ss.SSSSSS"
val formatter = DateTimeFormatter.ofPattern(TS_DATE_PATTERN)

val tsDate = formatter.parse(ts) // now the value as you would expect it...

将其转换为TimeStamp将按以下方式工作:

Transforming that to a TimeStamp will work as follows:

Timestamp.valueOf(LocalDateTime.from(tsDate))

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