LocalDateTime.parse 处的 java.time.format.DateTimeParseException

Question

为什么会出现以下代码：

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class TestProject {

    public static void main(String[] args) {
        String dateString = "2018-03-01T14:52:48Z";
        DateTimeFormatter dtf = DateTimeFormatter.ISO_INSTANT;
        LocalDateTime localDateTime = LocalDateTime.parse(dateString, dtf);
    }
}

抛出：

Exception in thread "main" java.time.format.DateTimeParseException: Text '2018-03-01T14:52:48Z' could not be parsed: Unable to obtain LocalDateTime from TemporalAccessor: {NanoOfSecond=0, InstantSeconds=1519915968, MilliOfSecond=0, MicroOfSecond=0},ISO of type java.time.format.Parsed
    at java.base/java.time.format.DateTimeFormatter.createError(DateTimeFormatter.java:1959)
    at java.base/java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1894)
    at java.base/java.time.LocalDateTime.parse(LocalDateTime.java:492)
    at org.bdshadow.TestProject.main(TestProject.java:11)
Caused by: java.time.DateTimeException: Unable to obtain LocalDateTime from TemporalAccessor: {NanoOfSecond=0, InstantSeconds=1519915968, MilliOfSecond=0, MicroOfSecond=0},ISO of type java.time.format.Parsed
    at java.base/java.time.LocalDateTime.from(LocalDateTime.java:461)
    at java.base/java.time.format.Parsed.query(Parsed.java:235)
    at java.base/java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1890)
    ... 2 more
Caused by: java.time.DateTimeException: Unable to obtain LocalDate from TemporalAccessor: {NanoOfSecond=0, InstantSeconds=1519915968, MilliOfSecond=0, MicroOfSecond=0},ISO of type java.time.format.Parsed
    at java.base/java.time.LocalDate.from(LocalDate.java:396)
    at java.base/java.time.LocalDateTime.from(LocalDateTime.java:456)
    ... 4 more

日期的字符串表示形式与 DateTimeFormatter.ISO_INSTANT 的 javadocs 中的完全一样：https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html#ISO_INSTANT。它在 java 9 中没有改变：https://docs.oracle.com/javase/9/docs/api/java/time/format/DateTimeFormatter.html#ISO_INSTANT

Answer 1

我相信是因为ISO_INSTANT 用于解析Instant

正如 javadoc 所说：

这是一个特殊的格式化程序，旨在允许java.time.Instant 的人类可读形式。

此代码有效：

    String dateString = "2018-03-01T14:52:48Z";
    DateTimeFormatter dtf = DateTimeFormatter.ISO_INSTANT;
    Instant instant = Instant.from(dtf.parse(dateString));

要使其成为本地日期时间，您可以使用：

LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, ZoneId.systemDefault())

这是对此类错误的一个很好的解释： Java SE 8 TemporalAccessor.from issues when used with a java.time.Instant object

Answer 2

LocalDateTime不t contain Zone in self. If you need parse string with zone useZonedDateTime`：

DateTimeFormatter dtf = DateTimeFormatter.ISO_INSTANT.withZone(ZoneId.systemDefault());
ZonedDateTime dateTime = ZonedDateTime.parse(dateString, dtf);