How to convert the MongoDB object id to a Java Date or Instant using Java

Question

The MongoDB ObjectID contains an embedded timestamp of its creation time. How can you extract this timestamp with plain Java without using classes of a driver library?

MongoDB creates object id's that typically look like:

5b86bd41840a1be5a55c7022
598af6efe4b09fc2332cf16a
598ad932e4b0f0f169b42d5f

The extraction target can be either a long, java.util.Date or a java.time.Instant.

Answer 1

Based on this page you could convert with these static methods the MongoDB ObjectID to a timestamp, java.util.Date or a java.time.Instant object:

public static Instant convertToInstantFrom(String objectId) {
    return convertToDateFrom(objectId).toInstant();
}

public static Date convertToDateFrom(String objectId) {
    return new Date(convertToTimestampFrom(objectId));
}

public static long convertToTimestampFrom(String objectId) {
    return Long.parseLong(objectId.substring(0, 8), 16) * 1000;
}

If you run the following code snippet:

public static void main(String[] args) throws ParseException {
    Stream.of("5b86bd41840a1be5a55c7022", "598af6efe4b09fc2332cf16a", "598ad932e4b0f0f169b42d5f")
            .map(SimpleTests::convertToInstantFrom).forEach(System.out::println);
}

You will see this result on the console:

2018-08-29T15:35:29Z
2017-08-09T11:50:07Z
2017-08-09T09:43:14Z