Difference between invokeMethod vs direct call

Question

I'm working in a company where there seem to be two ways that the developers called AM functions:
Direct Calling:
CompanyTakeoffAMImpl thisAM =
    (CompanyTakeoffAMImpl)pageContext.getApplicationModule(webBean);
thisAM.runSalesFunction(pageContext.getSalesId());invokeMethod calling
CompanyTakeoffAMImpl thisAM =
    (CompanyTakeoffAMImpl)pageContext.getApplicationModule(webBean);
Serializable[] userParam = { new Integer(pageContext.getSalesId()) };
Class[] userParamType = {Integer.class};
am.invokeMethod("runSalesFunction", userParam, userParamType);Is there any advantage / disadvantage to why we're doing this basic task in two different ways?
Which way is recommended?
Thanks

Answer 1

From the developer's guide:
+"If you need the server code to do some work for you, always route your calls through the root application module using the generic "remoteable" invokeMethod() method on the oracle.apps.fnd.framework.OAApplicationModule interface, or create an interface for your application modules so you can call typed methods, whose invocation can be checked at compile time. The application module can delegate or implement the logic as required."+
+"Note: The OAApplicationModule interface is in the oracle.apps.fnd.framework package and therefore, does not violate the rule stated in the first sentence of this bullet-point. All classes, interfaces, and exceptions in the oracle.apps.fnd.framework package can safely be used in both client and server code. If you opt to create an interface for your application module instead of using invokeMethod(), create this interface in the package directory immediately above your implementation. For example, the EmployeeAM interface for the oracle.apps.fnd.framework.toolbox.labsolutions.server.EmployeeAMImpl application module should be created in the oracle.apps.fnd.framework.toolbox.labsolutions package."+
Although I can't seem to find it at the moment, the developer's guide give the reason why you should not use AMImpl's from the controller. If I remember correctly, it has something to do with that it can't be assumed that the controller code will executed on the same tier at the AM.
The easiest thing to do it to create an interface as mentioned in the dev guide excerpts. This is quite easy to do. Double click your AM, then go to Client Methods, and shuttle over the ones you want to call from your controller. If your AM is custom.oracle.apps.fnd.server.MyAppModAMImpl, your interface will be custom.oracle.apps.fnd.MyAppModAM.
Just import custom.oracle.apps.fnd.MyAppModAM in your controller, and do:
MyAppModAM am = ( MyAppModAM ) pageContext.getApplicationModule( webBean );
This will also allow you to have compile time type checking.