What's the best way to define custom id generation as default in Grails?

Question

I want to switch my domain classes to use a variable length UUID for their ids. I don't want to simply display sequential ids on the URL for people to try and mess with. I've written a custom version of the Java UUID method to allow for variable length so I can have shorter ids for models that won't grow large.

I found this thread that explained how to modify the default mapping so I can change to 'assigned'. Modify Id generation for a Grails Plugin

What's the best way to also configure a default beforeInsert (to generate the custom UUID) and tell Grails I want to use strings for ids instead of integers?

I tried adding grails.gorm.default.beforeInsert to the config but that didn't work.

ataylor's answer below is the right way to do it in grails, but I've normally left the database generated IDs alone and added a different string/GUID field on the objects that needed some sort of correlation ID that might get exposed to the end user. That way, you get the normal join/foreign key behavior that grails/hibernate and databases have been tuned for (and writing SQL is easier), but when you need that external ID, you've got that too. — Ted Naleid, Nov 24 '10 at 01:14
That's what I've done before, but I read that you lose out on default cache that way since it does it by the id. And since I try not to do stuff against the db (or we have an alternate key) I'm gonna give this a shot. — ahanson, Nov 24 '10 at 15:55

ataylor · Accepted Answer · 2010-11-23T20:58:48.053

To make grails use strings for the ids, just declare a property String id. To populate it with a custom UUID, I'd use a hibernate id generator instead of beforeInsert. Create a class that extends org.hibernate.id.IdentifierGenerator, then add an id generator mapping like this to your domain class:

class MyIdGenerator extends IdentifierGenerator {
    Serializable generate(SessionImplementor session, Object object) {
        return MyUUID.generate()
    }
}

class MyDomain {
    String id
    static mapping = {
        id generator:"my.package.MyIdGenerator", column:"id", unique:"true"
    }
}

score 2 · Answer 2 · answered Aug 11 '13 at 12:44

This question is old but it's still showing up in searches. This currently the best way to do this, circa Grails 2.3. (I'm using postgres, so notice the "pg-uuid" type. Adapt this to your particular data store).

UUID uuid    
static mapping = {
    uuid generator: 'uuid2', type: 'pg-uuid'
    ...
}

What's the best way to define custom id generation as default in Grails?

2 Answers2

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