将具有给定偏移量的日期时间转换为 UTC Java

Question

鉴于我有字符串“2019-11-05/23:00”和偏移量“+07:00”，

我将如何在 Java(8) 中将其转换为 LocalDateTime UTC。

我当前的代码

@GetMapping("postDate/{date}")
public void testPost(@RequestParam("timezone") String timeZone, @PathVariable String date) {
    String format = "yyyy-MM-dd-HH:mm";
    String offset = timeZone;
    System.out.println(date);
    LocalDateTime timeWithOffset = LocalDateTime.parse(date,
                                                       DateTimeFormatter.ofPattern(format));

    System.out.println("\n\n\n" + timeWithOffset + "\n\n\n");

    // Cant Figure Out to get LocalDateTime timeInUTC
}

邮递员的请求

http://localhost:8080/postDate/2019-11-05-23:00?timezone=+07:00

Answer 1

您可以使用java.time 中的区域感知和偏移感知类。你会得到一个偏移量（我建议相应地命名参数，因为偏移量不是时区）和日期时间，这足以将同一时刻转换为不同的时区或偏移量。

看看这个例子并阅读 cmets：

public static void main(String[] args) {
    // this simulates the parameters passed to your method
    String offset = "+07:00";
    String date = "2019-11-05/23:00";

    // create a LocalDateTime using the date time passed as parameter
    LocalDateTime ldt = LocalDateTime.parse(date,
                                            DateTimeFormatter.ofPattern("yyyy-MM-dd/HH:mm"));
    // parse the offset
    ZoneOffset zoneOffset = ZoneOffset.of(offset);
    // create an OffsetDateTime using the parsed offset
    OffsetDateTime odt = OffsetDateTime.of(ldt, zoneOffset);
    // print the date time with the parsed offset
    System.out.println(zoneOffset.toString()
            + ":\t" + odt.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME));
    // create a ZonedDateTime from the OffsetDateTime and use UTC as time zone
    ZonedDateTime utcZdt = odt.atZoneSameInstant(ZoneOffset.UTC);
    // print the date time in UTC using the ISO ZONED DATE TIME format
    System.out.println("UTC:\t"
            + utcZdt.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
    // and then print it again using your desired format
    System.out.println("UTC:\t"
            + utcZdt.format(DateTimeFormatter.ofPattern("yyyy-MM-dd-HH:mm")));
}

我系统上的输出是：

+07:00: 2019-11-05T23:00:00+07:00
UTC:    2019-11-05T16:00:00Z
UTC:    2019-11-05-16:00

对于相反的情况（你得到一个 UTC 时间和一个偏移量并想要 OffsetDateTime），这可能会起作用：

public static void main(String[] args) {
    // this simulates the parameters passed to your method
    String offset = "+07:00";
    String date = "2019-11-05/16:00";
    // provide a pattern
    String formatPattern = "yyyy-MM-dd/HH:mm";
    // and create a formatter with it
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern(formatPattern);
    // then parse the time to a local date using the formatter
    LocalDateTime ldt = LocalDateTime.parse(date, dtf);
    // create a moment in time at the UTC offset (that is just +00:00)
    Instant instant = Instant.ofEpochSecond(ldt.toEpochSecond(ZoneOffset.of("+00:00")));
    // and convert the time to one with the desired offset
    OffsetDateTime zdt = instant.atOffset(ZoneOffset.of(offset));
    // finally print it using your formatter
    System.out.println("UTC:\t" + ldt.format(dtf));
    System.out.println(zdt.getOffset().toString()
            + ": " + zdt.format(DateTimeFormatter.ofPattern(formatPattern)));
}

输出是这样的：

UTC:    2019-11-05/16:00
+07:00: 2019-11-05/23:00