ABAP_to_the_Future

Building the WDA Application 12.2
next dream, wakes up from that, opens her eyes in the next dream, wakes up, and
repeats the process until she wakes up and opens her eyes back in reality. The
ALV grid data in our program must feel a bit like that. The request rushes down
from the view, through the controller, and into the mo del, which instantly asks
its database layer to handle this request, which in return delegates that task to, in
this example, the BOPF framework. Regardless of how the data is retrieved, once
it’s there it then starts its journey back up toward the view.
If You Are Not Using BOPF (But You Should Be Using BOPF!)
Even though this book uses the BOPF framework, it’s more than possible in real life that
you may be reusing an existing model class that has some other sort of data retrieval
mechanism, the most obvious being direct database reads using SELECT statements. If
this is the case, the only difference is that the box labeled BOPF Framework gets
replaced by a box saying SELECT Statements or Shared Memory or Read from External
System or whatever. Due to the highly encapsulated design approach used in this chapter,
nothing else needs to change.
An alternative to the somewhat convoluted process of passing a request through
several layers is to have one line of code inside the view (the SELECT statement).
At this point, anyone not used to the OO concept of abstracting everything will
think I’ve gone fruit loops, barking at the moon, free energy crazy. What do you
get from this seemingly ludicrous, overcom plicated level of abstraction? It’s all
about making the program antifragile so that you can change one part without
breaking the others. Namely, it has the following advantages:
왘 The database layer can decide to use something else than the BOPF, such as
shared memory, plain SQL reads, or something exotic, like calls to an external
system.
왘 At the other end of the scale, you can add a lot of new views that all show the
same data in different ways, and becaus e they all farm off the data request to
the other layers they’re all automaticall y synchronized rather than having the
lookup logic in each view.
왘 In the middle, the model is framework independent and can be used by other
frameworks, like ALV grid-based prog rams or “old-fashioned” DYNPRO programs.
In each case, due to the separation of concerns, you can only break one part at a
time. The parts of the application that are not adjacent to the box you have
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