Grails Plugins Requiring External Relationships

I posted this on the Grails 开发者_如何转开发mailing list yesterday and haven't had any hits. Figured I'd try here as well today.

I'm considering writing a grails plugin but this plugin would require some sort of relationship to an account / user object. However, I don't want to force a particular security model on the plugin. For example, say was writing a comment system plugin (I'm not). I'd have a comment object...

class Comment  {
   String comment
   Date dateCreated
   // etc etc
}

The comment is missing a couple of things:

1. Who added the comment
2. What the comment was added to.

I'd like to first focus on #1. So someone might be using the Spring security plugin and use the default Person object, or maybe they changed that to User. Who knows. Is there any way that anyone can think of to configure that relationship without hard coding it in the plugin?

One thing I've thought about was to have the grails app extend the plugin's domain classes to add this relationship. so I might do something like...

class ArticleComment extends Comment {
    static belongsTo = [user:User]
}

But in a larger plugin, that might be a lot of inheritance requirements. Not the end of the world, but just looking for other possible options.

You can use the same technique employed by the Commentable plugin:

The user of your plugin will need to declare a closure in Config.groovy to evaluate the logged user:

grails.myplugin.user.evaluator = { session.user }

And you can use something like this in your plugin's code to call the user configured closure:

def evaluateUser() {
    def evaluator = grailsApplication.config.grails.myplugin.user.evaluator
    def user 
    if(evaluator instanceof Closure) {
        evaluator.delegate = this
        evaluator.resolveStrategy = Closure.DELEGATE_ONLY
        user = evaluator.call()
    }

    if(!user) {
        throw new Exception("No [grails.myplugin.user.evaluator] setting defined or the evaluator doesn't evaluate to an entity. Please define the evaluator correctly in grails-app/conf/Config.groovy")
    }
    if(!user.id) {
        throw new Exception("The evaluated user is not a persistent instance.")
    }
    return user
}

I think you can do it like SpringSecurity do. Instead of let people extend your Comment class, You can write 2 class CommentUser & CommentPlace; then let others extends them. I think it's more simple.