Re: Depending between primary key in database and switch case statement

From:
Lew <lew@lewscanon.nospam>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 14 Jul 2007 10:02:59 -0400
Message-ID:
<24CdneT_3e8JSgXbnZ2dnUVZ_tijnZ2d@comcast.com>
Daniel Pitts wrote:
  you might consider using polymorphism instead. I.E. create a

ChecksErrors interface and an implementation of that interface for
every ErrorID. Then have a lookup table (probobably Map<Integer,
ChecksErrors> or ChecksErrors[], depending on the range of ErrorID).

Hope this helps.
Daniel.

P.S. Hard coding behavior is NOT a bad thing. You're programs behavior
is to do something different depending on the ErrorID, so having a
"hard coded" switch in this case is not a Bad Thing.


The polymorphic handler idea is very powerful, and it's how frameworks like
Struts and JSF work, for example. The lookup table can be instantiated from a
resource like a property file at program initialization.

When confronted with a switch off of an (essentially) enum value set,
polymorphism is usually the better choice. Plug in the handler that would've
been the method reached from the switch, but is now a class implementing a
common handle() (or do(), execute(), whatever()) method that knows how to
handle its use case.

The Map can be Map< ErrorID, Class<? extends ChecksErrors>>, that way you can
instantiate a new handler for each invocation instead of worrying about
re-using the same handler object each time.

--
Lew

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