Re: Law of Demeter and accessing classpath resources

From:
chrislewis <burningodzilla@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 21 Sep 2009 12:46:40 -0700 (PDT)
Message-ID:
<bf140c7b-a18b-43a0-b68c-98ad4e7879b3@p23g2000vbl.googlegroups.com>
Thanks for all the responses. I'm not sure which tool you are saying
is broken, but there is still the potential issue of consistent unit
tests. In this case, as has been pointed out, the api is very stable.
However, because the contents of the classpath are environmental, unit
tests will still be forced to make environmental assumptions (for
example, that /resource.gif is present). In my case that shouldn't be
a problem, and abstracting it further wouldn't buy me anything. Thanks
again!

chris

On Sep 21, 2:02 pm, Steven Simpson <s...@domain.invalid> wrote:

chrislewis wrote:

URL resourceUrl = this.getClass().getClassLoader().getResource
(resourceName);

According to what Clean Code says about the Law of Demeter, it seems
like this is Bad Thing, as I'm calling a method on an object yielded
through chained calls (not to mention the class loader could be
considered a global resource).


I had to read up on LoD from Wikipedia, and noticed from a quick scan
that, among other things, it says:> an object A can request a service (ca=

ll a method) of an object

instance B, but object A cannot =93reach through=94 object B to access =

yet

another object, C, to request its services. Doing so would mean that
object A implicitly requires greater knowledge of object B's internal
structure.


<http://en.wikipedia.org/wiki/Law_of_Demeter>

Well, that surely doesn't apply here. getClass() is part of the public
contract of 'this', not internal structure. Same goes for
getClassLoader() on a Class.

From reading on, I get the impression that the article is talking about
genuine member objects - not mere references. Since that can't strictl=

y

happen in Java, the nearest thing is that an object contains a reference
to some resource exclusive to that object. An Object certainly doesn't
exclusively reference a Class, nor does a Class exclusively reference a
ClassLoader, so again, I don't think it applies.

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