Java / Kotlin：为什么Jackson解析日期与SimpleDateFormat不同？

Question

I'm sure this is some form of user error, but I can't puzzle out what I'm doing incorrectly.

I have a Kotlin data class that with a constructor field like this:

data class CronEvent(
    @JsonFormat(
            shape = JsonFormat.Shape.STRING,
            pattern = "yyyy-MM-dd'T'HH:mm:ss'Z'"
    )
    @JsonProperty("time")
    val time: Date
 )

This gets populated by ObjectMapper that accepts a json string as a payload. For my unit test, I have a SimpleDateFormat object that I instantiate with the same pattern.

val jsonStream = CronEventTests::class.java.classLoader.getResourceAsStream("CronEventPayload.json")
val cronEvent = jsonStreamToCronEvent(jsonStream)
// ...
val simpleDateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'")
val expectedDate = simpleDateFormat.parse("2018-01-15T00:48:43Z")
cronEvent.time shouldBe expectedDate

The json file ( CronEventPayload.json ) that I load in my unit test has the exact same date string ( 2018-01-15T00:48:43Z ) yet my test fails.

java.lang.AssertionError: expected: Mon Jan 15 00:48:43 MST 2018 but was: Sun Jan 14 17:48:43 MST 2018
Expected :Mon Jan 15 00:48:43 MST 2018 
Actual   :Sun Jan 14 17:48:43 MST 2018

They have the same input and are utilizing the same date format string, but they're clearly different. Why are these two dates not the same?

Answer 1

The default timezone for @JsonFormat is UTC . You can override with the timezone attribute of the annotation.

The default timezone for SimpleDateFormat is your local timezone ( MST , reading from your output)

Make sure that the timezones match. You can add the line:

simpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));

just below the construction of your SimpleDateFormat .

Although your dates in their text format contains the timezone (the Z at the end, meaning UTC ), you're using a format that just treats the Z as a literal character, you're not interpreting it as a timezone.