How to Tell Time in Java’s Garbage Collection

I found this interesting article¹ on clock drifts and hardware clocks and OS clocks and Java and logging.

I really liked the quote in there:

“A person with a watch knows what time it is. A person with two watches is never sure.”

- Segal's Law

References

[1] How to Tell Time in Java’s Garbage Collection

https://devblogs.microsoft.com/java/how-to-tell-time-in-javas-garbage-collection/

XMLGregorianCalendar off by a few days on dates before 1582

Oh, darn. Just got bit by this thing.

The customer had stored documents for which it did not know the date with date 01-01-0007.

When importing it via XML, it turned out wrong.

The reference [1] below explains why.

References

[1] StackOverflow - Date change when converting from XMLGregorianCalendar to Calendar

https://stackoverflow.com/questions/16321193/date-change-when-converting-from-xmlgregoriancalendar-to-calendar

Wikipedia - Proleptic Gregorian Calendar

https://en.wikipedia.org/wiki/Proleptic_Gregorian_calendar

Freemarker and java.time

I noticed that Freemarker¹ does not yet support the Java SE 8 Date and Time². I noticed this, because I tried it. It just tries to parse the toString() and it fails.

There's already blogs about it.

So I had to add a little dependency to provide this, courtesy of Jakob Vad Nielsen³.

<dependency>
    <groupId>no.api.freemarker</groupId>
    <artifactId>freemarker-java8</artifactId>
    <version>1.1.5</version>
</dependency>

Of course, it's not native support, you still have to call specific methods to parse this. But it works in my case.

It means I have to change some of my templates around, as described below:

Published Date ${blog.createDate?datetime}

Instead should be:

Published Date ${blog.createDate.format()}

References

[1] FreeMarker Java Template Engine

https://freemarker.apache.org/

[2] Java Technical Details - Java SE 8 Date and Time

https://www.oracle.com/technical-resources/articles/java/jf14-date-time.html

[3] GitHUb - Java library adding support for the Java 8 java.time api to FreeMarker.

https://github.com/lazee/freemarker-java-8