By meaning facade is some kind of an abstraction.
Lets say that when you want to access the a number of entities. Say u r the teacher and u want to see the attendance of students, if u want to see any important notice on the notice board on the site and so on and so forth.
you would create a facade so that that object calls all these entities and not you.
It does the following
- reduces network
- helps maintain transaction across entities
by definition a delegate refers to a representative. a business delegate is supposed to be a business representative.
So if u have a business service available, u would create a business represntative on the presentation layer so that the presentation layer is independent of the business/service layer
- hides the complexity of an application to connect to the business systems
- enables easy development since now the presentation layer can work independently of service layer
- it can cache data thats on the server side so to as to decrease the round-trip
Typically a sytem would be
Servlet -- Action Object -- BusinessDelegate -- SessionFacade -- Entities -- Back-End system
Some place where experience helps and certifications dont