A Groovy hook is a N4 Groovy Plug-in that is deployed with a specific name (convention). You can think of a Groovy hook as dynamically inline'ing Groovy code into the N4 code. N4 automatically loads and treats a groovy class (hook) as a business-flow interceptor that is invoked at a particular point in the application flow allowing extra validations.
The table in this document summarizes the current Groovy hooks available in N4.
We do not recommend you use Groovy hooks (interceptors) to modify N4 data.
Also, note that these (named) Groovy hooks are in addition to other groovy capabilities in N4, such as:
WebServices Custom Groovy Code Injection
JMS Using Direct Code Injection
Custom Code in N4 Gate
Script Runner
Groovy Plug-ins
The various Groovy capabilities differ in deployment methods; but, once deployed Groovy in any form extends or intercepts the N4 business flow.
Framework-based Groovy
Starting with N4 v. 2.0, Navis supports Framework-based Groovy, such as the Entity Life Cycle Interceptors (LCI). You can also use the LCI to validate the persisted fields for an entity.