How to set parameters on Groovy/Grails InvokeHelper.invokeMethod()

问题

I have a Grails webapp running a Spring Integration inbound-channel-adapter that is configured to receive emails and there is a service activator that processes the message. This service activator pulls out pieces and parts of the email based on business rules and then needs to update Grails domain objects and save those changes to the database.

Spring Integration service activator code snippet:

HashMap<String, Serializable> params = new HashMap<String, Serializable>();
params.put("notification", notification );
params.put("notificationType", notificationType );
params.put("sender", notificationSender );
InvokerHelper.invokeMethod(NotificationCreationService.class, "createNotification", params);

Grails NotificationCreationService action snippet:

def static createNotification() {
    if (params.notification != null && params.notificationType != null && params.sender != null) {
        String notification = params.get("notification") as String
        NotificationType notificationType = params.get("notificationType") as NotificationType
        String sender = params.get("sender") as String

        def NotificationMessage notificationMessage = null
        notificationMessage = new NotificationMessage()
        notificationMessage.notification = notification
        notificationMessage.save(flush: true)
        ...
    }
}

NotificationMessage is a standard Grails domain class

Error generated:

org.springframework.integration.MessageHandlingException: 
    groovy.lang.MissingMethodException: No signature of method: mycompany.pyproject.mypackage.NotificationMessage.save() is applicable for argument types: () values: []
    Possible solutions: save(), save(boolean), save(java.util.Map), wait(), any(), wait(long)

If I change createNotification() to not be static then I get the following:

org.springframework.integration.MessageHandlingException: 
    groovy.lang.MissingMethodException: No signature of method: static mycompany.pyproject.mypackage.NotificationCreationService.createNotification() is applicable for argument types: (java.util.HashMap) values: [...]       
    Possible solutions: createNotification(java.util.HashMap), createNotification(java.lang.String, napa.changedetection.alert.NotificationType, java.lang.String)

I've tried other combinations of InvokeHelper.invokeMethod() and the definitions of the Grails actions with similar results. InvokeHelper has several other methods for invoking methods as well as setting different properties, but I haven't found the magic combination to make this work and any internet searched have turned up very little as far as example code for InvokeHelper.

Ideally, the Grails action would not be static and it would use the standard params mechanism. This would allow me to call the same action directly from the Grails code as well as from the Spring Integration service activator via the InvokeMethod functionality.

Does anyone have any thought on how to tie this together?