How to generate time based UUIDs?

问题:

I want to generate time based UUID in java - java.util.UUID.randomUUID() genrates a UUID version 4. How to generate a version 1 (time based) UUID ? Is there a separate library for that or is it some how provided in the Java 7 API and I am missing it.

回答1:

Be very careful using com.eaio.uuid.UUID, if you need to generate GUID by time other than current time, as this will always generate the same UUID for given time. So if your data has requirement to generate UUID, where records may have same time, this will generate same UUID.

We needed this to generate UUID for records, which are created ahead and also multiple records at same time, we tried to tweak it by trying to use UUIDGen.createTime(). We found that it has a side effect to mutate the time for records out of order. If a subsequent request to create UUID has a time stamp older than previous request, you end up having a UUID, which is based on previous request's time stamp.

After all the analysis, we had to simply go back to create UUID at the time of creation, so that we don't have to pass it as an argument. Whichever solution we come up with to generate UUID at a later time, every one has a drawback.

回答2:

String timeuuid = com.datastax.driver.core.utils.UUIDs.timeBased().toString(); 

have a look at https://docs.datastax.com/en/drivers/java/2.0/com/datastax/driver/core/utils/UUIDs.html

回答3:

FasterXML Java Uuid Generator (JUG)

https://github.com/cowtowncoder/java-uuid-generator

UUID uuid = Generators.timeBasedGenerator().generate(); 

文章来源: How to generate time based UUIDs?