使用Java 8转换日期时间字符串，例如Joda DateTime（String） [英] Convert date time string like Joda DateTime(String) with Java 8

问题描述

我有一个API可以以三种可能的格式返回JSON中的日期值：

I have an API that can return date values in JSON in three possible formats:

1. 2017-04-30T00：00 + 02 ：00


2. 2016-12-05T04：00


3. 2016-12-05

我需要将所有三个都转换为 java.time.LocalTimeDate 。 Joda在 DateTime 对象上有一个不错的构造函数，该函数采用所有三种格式作为Strings并将其转换。 DateTime dt = new DateTime（StringFromAPI）; 就足够了。

I need to convert all three into a java.time.LocalTimeDate. Joda has a nice constructor on the DateTime object which takes in all three formats as Strings and converts them. DateTime dt = new DateTime(StringFromAPI); is enough.

Java 8中是否有类似的功能（ java.time 包）？看来我现在首先必须正则表达式 String 来检查格式，然后创建一个 LocalDateTime ， ZonedDateTime 或 LocalDate 并将后者2.转换为 LocalDateTime 。对我来说似乎有点麻烦。有一个简单的方法吗？

Is there a similar capability in Java 8 (java.time package)? It seems I now first have to regex the String to check the format, then create either a LocalDateTime, ZonedDateTime or LocalDate and convert the latter 2. to LocalDateTime. Seems a bit cumbersome to me. Is there a easy way?

推荐答案

我提出了两种选择，每种选择都有其优缺点。

I am presenting two options, each with its pros and cons.

一个，建立自定义 DateTimeFormatter 以接受您的三种可能的格式：

One, build a custom DateTimeFormatter to accept your three possible formats:

public static LocalDateTime parse(String dateFromJson) {
    DateTimeFormatter format = new DateTimeFormatterBuilder().append(DateTimeFormatter.ISO_LOCAL_DATE)
            .optionalStart()
            .appendLiteral('T')
            .append(DateTimeFormatter.ISO_LOCAL_TIME)
            .optionalStart()
            .appendOffsetId()
            .optionalEnd()
            .optionalEnd()
            .parseDefaulting(ChronoField.HOUR_OF_DAY, 0)
            .toFormatter();
    return LocalDateTime.parse(dateFromJson, format);
}

一方面，它很干净，另一方面，有人可以轻松找到它有点棘手。对于问题中的三个示例字符串，它会产生：

On one hand, it’s clean, on the other, someone could easily find it a bit tricky. For the three sample strings in your question it produces:

2017-04-30T00:00
2016-12-05T04:00
2016-12-05T00:00

另一个选择，尝试三个依次选择不同的格式：

The other option, try the three different formats in turn and pick the one that works:

public static LocalDateTime parse(String dateFromJson) {
    try {
        return LocalDateTime.parse(dateFromJson);
    } catch (DateTimeParseException e) {
        // ignore, try next format
    }
    try {
        return LocalDateTime.parse(dateFromJson, DateTimeFormatter.ISO_OFFSET_DATE_TIME);
    } catch (DateTimeParseException e) {
        // ignore, try next format
    }
    return LocalDate.parse(dateFromJson).atStartOfDay();
}

我不认为这是最漂亮的代码，仍然有人认为它是比第一种选择更直接？我认为仅依靠内置的ISO格式就可以保证质量。您的三个示例字符串的结果与上面相同。

I don’t consider this the most beautiful code, still some may think it’s more straightforward than the first option? I think there’s a quality in relying on the built-in ISO formats alone. The results for your three sample strings are the same as above.

这篇关于使用Java 8转换日期时间字符串，例如Joda DateTime（String）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！