Jigsaw prototype, take 2

David M. Lloyd david.lloyd at redhat.com
Wed Sep 4 17:50:34 PDT 2013

On 09/04/2013 05:27 PM, mark.reinhold at oracle.com wrote:
> 2013/8/30 5:20 -0700, david.lloyd at redhat.com:
>>                       ...  In addition, many best practices have emerged
>> that (partially or wholly) contradict the original design intent of
>> these systems (OSGi also falls into this category).
> Do you have links to any good descriptions of these best practices?
> That'd be helpful.

Not a lot as links, as mostly they are "community knowledge" among our 
various teams, but here's a couple for each that I can find relatively 

For Maven:

* Version ranges considered harmful [1] [2] [3] [4] (and probably more); 
we disallow them within our own products for stability reasons
* Transitive-by-default causes problems in mid to large projects due to 
extensive conflicts [can't find the discussion...]; fix is to use and 
verify exclusions, specify "provided" scope, and use 
maven-enforcer-plugin [5] to ban transitive dependencies

For OSGi:

* Using the full capabilities of range dependencies can cause resolution 
to be NP-complete; best practice is to use ranges in a more restricted 
manner [6]
* Require-Bundle not recommended due to lack of hiding non-public 
packages among other things [no link] (however, to be fair this is only 
due to the way Require-Bundle was designed; it's not an inherent flaw, 
but it is a best practice not to use it, hence it fits the criteria)

As with many so-called "best practices" there are those who disagree 
with some or all of them; I'm not going to argue the finer points of 
each one.  I'm just pointing out that just copying a given mechanism and 
adapting it straight to a somewhat similar but also somewhat different 
use case is doubly dangerous - on one hand, it is hard to know what went 
into the design of these mechanisms; and on the other hand, there is a 
considerable base of knowledge that comes from third parties (or just 
the general public) that sheds additional light on the pros and cons of 
these mechanisms as well.

[2] http://stackoverflow.com/a/7169847/2033093
[3] http://stackoverflow.com/a/3882490/2033093
[4] http://grokbase.com/p/maven/users/129vwgkd1c/version-ranges-not-working
[6] http://wiki.apidesign.org/wiki/RangeDependenciesAnalysed


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