Document expected format for commit.time and build.time in git.properties

[allnightlong]

For this specific date format GitProperties converting it back to timestamp, so it's not possible to format my git commit date with this template.

spring-boot/spring-boot/src/main/java/org/springframework/boot/info/GitProperties.java

Line 106 in 4a8d353

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");

[wilkinsona]

Sorry, I don't understand the problem that you're trying to report.

The time is deliberately converted to epoch time so that it's in a consistent format. This time is then exposed as a Date. Typically, this Date will be serialised to JSON by Jackson when looking at Actuator's info endpoint. The formatting can then be controlled by Jackson's configuration (serialisation of dates as timestamps, date format, etc).

Can you please describe your problem in more detail? A detailed description of the behaviour that you are seeing and the behaviour that you expect to see would be useful. A failing test case would be even better.

[allnightlong]

Sure, I can describe the case.
I'm using 'com.gorylenko.gradle-git-properties' gradle plugin (https://github.com/n0mer/gradle-git-properties) to add git.properties to my jar.
This plugin provides 2 params: 'dateFormat' and 'dateFormatTimeZone' (names are self-explanatory)

So if I provide any correct dateFormat to my gradle.properties file, I'm basically getting what I'm expecting. For example, for dateFormat = "yyyy-MM-dd'T'HH:mmZ", I've got such json from my /info endpoint:

Hence, there is no seconds in this date format.

But for one specific dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ", spring-boot formats my time to currentTimeMillis:

First of all, this is counter-intuitive (honestly, I've spend quite some time to get to the very reason of that). I would ignore this date format, but, apparently, it's ISO 8601 format, which is kinda useful for my purposes.

If it is difficult to change this behavior to more predictable due to compatibility issues, may be it is possible to provide 2 fields in resulting json: 1st is changed and 2nd - unchanged?

[wilkinsona]

Thanks, I think I understand what's happening now.

Boot's GitProperties expects the commit time to be formatted with yyyy-MM-dd'T'HH:mm:ssZ. When it is, that value is coerced into a long (epoch time) and then exposed as a Date. This is what's happening in your second example. Jackson has formatted the Date as a timestamp (presumably because that's what you've configured it to do).

When the commit time doesn't match the expected format it's left as-is and as a String. With management.info.git.mode=full enabled it's then exposed as a String in that format and won't be affected by Jackson's date formatting configuration as Jackson has no way of knowing that it's a date.

When you use yyyy-MM-dd'T'HH:mm:ssZ as the format for the time in git.properties, Boot is currently working as designed and you need to configure Jackson to serialise the Date into your desired format. This is the recommended approach as it means that commit time will be formatted the same as any other Date that your application serialises to JSON.

Given that both the Maven and Gradle plugins for generating git.properties allow the date format for the commit time to be configured, we should document the expected format for the commit time in git.properties so that users can configure it as required.