ZonedDateTime经杰克逊往返产生不等ZonedDateTime

Question

考虑到以下单元测试：

@Test
public void zonedDateTimeCorrectlyRestoresItself() {

    // construct a new instance of ZonedDateTime
    ZonedDateTime now = ZonedDateTime.now(ZoneId.of("Z"));
    // offset = {ZoneOffset@3820} "Z"
    // zone   = {ZoneOffset@3820} "Z"

    String converted = now.toString();

    // restore an instance of ZonedDateTime from String
    ZonedDateTime restored = ZonedDateTime.parse(converted);
    // offset = {ZoneOffset@3820} "Z"
    // zone   = {ZoneOffset@3820} "Z"

    assertThat(now).isEqualTo(restored); // ALWAYS succeeds
}

@Test
public void jacksonIncorrectlyRestoresZonedDateTime()  {

    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.findAndRegisterModules();
    objectMapper.disable(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE);

    // construct a new instance of ZonedDateTime
    ZonedDateTime now = ZonedDateTime.now(ZoneId.of("Z"));
    // offset = {ZoneOffset@3820} "Z"
    // zone   = {ZoneOffset@3820} "Z"


    String converted = objectMapper.writeValueAsString(now);

    // restore an instance of ZonedDateTime from String
    ZonedDateTime restored = objectMapper.readValue(converted, ZonedDateTime.class);
    // offset = {ZoneOffset@3820} "Z"
    // zone   = {ZoneOffset@3821} "UTC"

    assertThat(now).isEqualTo(restored); // NEVER succeeds
}

而这个解决办法是：

@Test
public void usingDifferentComparisonStrategySucceeds() throws Exception  {

    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.findAndRegisterModules();
    objectMapper.disable(DeserializationFeature.ADJUST_DATES_TO_CONTEXT_TIME_ZONE);

    // construct a new instance of ZonedDateTime
    ZonedDateTime now = ZonedDateTime.now(ZoneId.of("Z"));
    // offset = {ZoneOffset@3820} "Z"
    // zone   = {ZoneOffset@3820} "Z"

    String converted = objectMapper.writeValueAsString(now);

    // restore an instance of ZonedDateTime from String
    ZonedDateTime restored = objectMapper.readValue(converted, ZonedDateTime.class);
    // offset = {ZoneOffset@3820} "Z"
    // zone   = {ZoneOffset@3821} "UTC"

    // the comparison succeeds when a different comparison strategy is used
    // checks whether the instants in time are equal, not the java objects
    assertThat(now.isEqual(restored)).isTrue(); 
}

我想我是想弄清楚为什么杰克逊内部不打电话给ZonedDateTime.parse()？就我个人而言，我认为这是杰克逊的一个缺陷，但我没有足够的信心来为它打开一个问题，只是没有一些反馈。

Answer 1

引用维基百科的ISO 8601

如果时间为UTC，则在没有空格的时间之后直接添加一个Z。Z是零UTC偏移量的区域指示符。因此，"09:30 UTC"被表示为"09:30Z"或"0930Z"。"14:45:15 UTC"将是"14:45:15Z"或"144515Z"。 UTC时间也被称为祖鲁时间，因为祖鲁是北约字母Z的拼音词。

Z不是一个区域。UTC是区域，然后使用格式化字符串中的Z表示该区域。

永远不要使用ZoneId.of("Z")。这是错误的。