Hooking into Grails Domain object save()

Question

I'm writing a grails plugin and I need to hook into the domain save() method to do some logic after the save. I need to do this across multiple domain classes. I'm trying to avoid hibernate events in the cases where a plugin user is not using hibernate with GORM.

I've tried many thing but below is what I think should have had the best chance at working. In all cases grailsSave is null. How can I do this?

def doWithDynamicMethods = { ctx ->
    application.domainClasses.each { dc ->
        def grailsSave = dc.metaClass.pickMethod('save', [Map] as Class[])

        domainClass.metaClass.save = { Map params ->
     grailsSave.invoke(delegate, [params] as Object[])
     println "Saved object, now do my thing"
     //...
        }
    }
}

I have the following set in my *Plugin.groovy class:

def dependsOn = [domainClass: '1.1 > *', hibernate: '1.1 > *']
def loadAfter = ['hibernate']

Answer 1

Wouldn't this best be added to the service class that owns the unit of work? That's where the usual Spring/Grails idiom would have such logic. You needn't modify the save at all.

Answer 2

There are three different version of save added to the metaClass,

save(Map)
save(Boolean)
save()

Which one are you calling in your testing? You'll need to add you code to each one.

Another thing to check is whether your plugin is running after the hibernate plugin which adds the three methods to the metaClass

cheers

Lee

Answer 3

Have a look at the Falcone Util plugin. This plugin allows you to hook into Hibernate events (see documentation at the bottom of the page). I don't know if this is exactly what you want, but you might get some hints.

Ps! I don't think the plugin works with Grails 1.2 yet.

Answer 4

I was unable to successfully get a reference to the save() methods during plugin/app initialization; I don't know why. Instead, I decided to create a listener for the hibernate events after insert, update, and deletes. This post by Sean Hartsock regarding the Audit Logging plugin was a perfect primer for doing that.

Here's the gist of the Listener:

class MyListener implements PostInsertEventListener, PostUpdateEventListener, PostDeleteEventListener, Initializable {

        public void onPostInsert(final PostInsertEvent event) {
            // logic after insert
            return
        }

        public void onPostUpdate(final PostUpdateEvent event) {
            // logic after update
            return
        }

        public void onPostDelete(final PostDeleteEvent event) {
            // logic after delete
            return
        }


        public void initialize(final Configuration config) {
            return
        }   
    }

Then in the *GrailsPlugin.groovy:

def doWithApplicationContext = { applicationContext ->

    // add the event listeners for reindexing on change
    def listeners = applicationContext.sessionFactory.eventListeners
    def listener = new MyListener()

    ['postInsert', 'postUpdate', 'postDelete'].each({
       addEventTypeListener(listeners, listener, it)
    })

}


// copied from http://hartsock.blogspot.com/2008/04/inside-hibernate-events-and-audit.html
private addEventTypeListener(listeners, listener, type) {
    def typeProperty = "${type}EventListeners"
    def typeListeners = listeners."${typeProperty}"

    def expandedTypeListeners = new Object[typeListeners.length + 1]
    System.arraycopy(typeListeners, 0, expandedTypeListeners, 0, typeListeners.length)
    expandedTypeListeners[-1] = listener

    listeners."${typeProperty}" = expandedTypeListeners
}

Fairly simple at the end of the day...

Answer 5

This is an issue of premature optimization: older versions of Groovy seriously penalized MetaClass mangling, and so GORM does not add all of its magic until it detects the need to.

Easiest solution is to have your plugin dependOn GORM Labs (I work around it there). The alternative solution is to trigger methodMissing manually (which would be duplicating the work I did). See the GORM Labs documentation for details on how I accomplished that.