Great read, although a little "hostile" to newcomers maybe. :) The parts about class loading might, as others have suggested, be a bit too complex for us average java developers too. I certainly didn't know about this before starting with OSGi. And I still have alot to learn of course! And I believe this is the place where OSGi has the most left to do. Class loading is an implementation detail that shines through. When I declare a method to be private, I never have to worry about how the JVM enforces that. In the same sense, I shouldn't have to worry about how OSGi enforces package visibility. But that's another story.
Also, I think a presentation like this is a great place to emphasize the difference between "jar dependency management" and "package dependeny management". Had I read the presentation a few years back (two maybe) before having started to "Felix" (yes, it's a verb now), I might have thought "Well, maven does most of this for me, and without those silly restrictions!.". It is a profound point about OSGi that might be easily missed when reading "starter materail". But I guess one can't cover everything at every possible depth. And you do talk about it, and you do mention versions. I just think that the whole "per package!!" idea might get lost between all modules, jars and cookies. :) A module is a set of packages, depending on other modules with packages. A module is not a jar with classes depending on other jars with classes (as with maven). And of course, to further shoot down "maven does it for me"-like arguments, slam a big "services means *modularized* *dynamism*" sticker on top of every page. Ok, don't... But, as I said, people might get the impression that OSGi is a way to manage your jars - when it can actually cook and wash your car too. As said, very interesting read! In fact, it got me wondering about a few things so I'm off asking questions in a mail list near you! Thanks! :) Regards, Per-Erik Svensson On Thu, Jan 20, 2011 at 5:32 PM, Richard S. Hall <[email protected]>wrote: > > On 1/20/11 10:47, [email protected] wrote: > >> Thanks for doing this Richard! >> >> I like the sound of OSGi but I've never made the leap to it because I >> don't feel that I understand it well enough to convince myself that it is >> the right direction to go in. >> >> Your slides have clarified a number of things for me and your analogies >> are both clever and funny! I found the slides very easy to follow but I >> found myself getting confused in the "Understanding search order" and "When >> things go wrong..." sections, I think partially because I don't have a solid >> grasp of the terminology. What is class loader delegation? >> >> I am familiar with the notion of dependency management from my experiences >> with using Maven to build my projects so I can somewhat follow you in the >> "When things go wrong..." section where you first mention transitive >> dependencies. However, old school developers that are stuck using Ant might >> find it more difficult. You touch on the subject in various places but I >> think it would be helpful if you had a couple of slides that briefly talked >> about dependency management in the context of OSGi before moving on to >> troubleshooting. >> > > Those two sections will be the most difficult to follow, for sure, so > you'll just have to catch me presenting it sometime. :-) > > Seriously, though, I am already working on improving that section by trying > to improve the error messages printed by the Felix framework. I will see if > there is anything else I can do to add some more introductory overview for > class loaders (without adding too many more slides). > > -> richard > > > >> Cheers! >> -John >> >> Quoting "Richard S. Hall" <[email protected]>: >> >> After some recent experiences I had with some developers trying to use >>> OSGi without even understanding the basics, I decided to work on a >>> presentation highlighting what you must understand about OSGi to use >>> it. Please find it on the presentations page: >>> >>> http://felix.apache.org/site/presentations.html >>> >>> The direct link to the PDF is here: >>> >>> >>> >>> http://felix.apache.org/site/presentations.data/Learning_to_ignore_OSGi.pdf >>> >>> Comments welcome. >>> >>> -> richard >>> >>> --------------------------------------------------------------------- >>> To unsubscribe, e-mail: [email protected] >>> For additional commands, e-mail: [email protected] >>> >> >> >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> >> > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > >
