On Jun 29, 12:27 pm, Augusto <augusto.sellh...@gmail.com> wrote: > No I mean that exactly. > > I don't know, I mean the point of modularizing something for me is I > may want to use your module but I don't care about its internals. Or > at most, I don't want the internals of your module to affect me.
[disclaimer: I contribute to OSGi projects and I'm co-authoring a book on OSGi] exactly, that's why libraries often use tools to embed/repackage dependencies: http://maven.apache.org/plugins/maven-shade-plugin/ http://code.google.com/p/jarjar/ for example Guice has CGLIB and Google-Collections as internal dependencies, but I wouldn't want to be forced to use the same version of these libraries when using Guice - similarly the Guice team probably doesn't want to be bothered with problems caused by someone putting a different version of CGLIB before Guice on the classpath (the JVM will pick the first matching class when scanning the classpath, so ordering makes a big difference when there's overlapping content) so Guice repackages CGLIB and Google-Collections inside the jar - unfortunately this means anyone who already has those jars gets duplicate content (~400k?) now imagine if everyone does the same - you could end up with ten copies of the Google-Collection classes, embedded inside various libraries - you can already see this happening in applications today, and it's caused by a lack of modularity if there was a standard modularity system that supported multiple versions then the Guice team could distribute just their classes (plus the necessary metadata) safe in the knowledge that regardless of what jars were on the 'module' path, the right version would be wired to Guice that's one of the reasons why I find module systems compelling - now I can totally understand why you might need a special framework to modularize the JVM, just like the JVM has the "Unsafe" class for internal use - but I'm a little bit wary about using the same solution for applications, exactly because it might be optimized for the JVM (for example the "no multiple versions" requirement) still hoping that JSR 294 will help bring both sides together in some way... oh well, time will tell - I'd hate for people to be put off the general idea of modularity (and to some extent programming to interfaces) as imho it does lead to better apps -- Cheers, Stuart PS. many thanks to the JavaPosse for doing both of the interviews in the first place > So yeah, you can expect your 3rd party libraries to "keep up" with the > latest and greatest, but that's kind of an unreasonable expectation > with fast paced technology. What I want is to use your library, but > not have it affect the same libraries it might be using internally but > that I explicitly depend on. > > BTW, when people say "classpath hell" (or jar hell) this is one of the > main scenarios they refer to. > > http://c2.com/cgi/wiki?ClasspathHell > > ---------- > One big need for OsGi / JavaModuleSystem? (JSR 277) functionality is > to fix the ClasspathHell problem: > > * My application uses libraries "B" and "C", both of which use > library "D". > * But "B" and "C" require different versions of "D". > * There's no version of "D" I can put on the CLASSPATH that will > satisfy both "B" and "C". > * Thus, I'm in "ClasspathHell" -- there's no "standard Java way" > to fix the problem. > ------------ > > I assume that the whole "Application Context" in Jigsaw means that for > webapps and apps running in an EJB container you can overcome this but > no I meant it more in a regular application outside of any of these > containers. > > Augusto > > On Jun 28, 11:21 pm, Jess Holle <je...@ptc.com> wrote: > > > Augusto wrote: > > > On Jun 28, 6:38 pm, Steve <stephen.a.lind...@gmail.com> wrote: > > > >> If an alternative modularity platform for app developers was more > > >> compelling than OSGi I certainly would jump ship, but it would need to > > >> at least provide what the OSGi core does now (proper component > > >> encapsulation, supporting multiple versions of the same 3rd party jar, > > >> runtime dynamism, etc.). > > > > Multiple versions of the same jar is one thing I described in my blog > > > post incorrectly. Well, I said that was a core problem solved by a > > > module system but in fact Jigsaw doesn't seem to support it. It is not > > > needed for modularizing the JDK, but it is essential for modularizing > > > applications. > > > It is essential for /some/ applications. > > > Personally I generally prefer to make all the parties involved work > > /really/ hard at allowing for and arriving at a single version of any > > given library (ideally the latest stable version) to be used at runtime > > rather than allowing multiple versions within an application. Using > > multiple library versions in one application is pretty much a worst case > > scenario to me -- and is generally a strong indication that someone is > > not keeping their software up-to-date (i.e. so that it can use the > > latest stable versions of the libraries it depends on). If that someone > > is a vendor or 3rd-party component then that's generally a sign to go > > shopping for another one -- unless, of course, you're the one who has > > been foolish enough to stay on an old version of that component instead > > of moving to the new version, in which case it is time to upgrade. > > > -- > > Jess Holle > > > P.S. If you mean multiple versions just for things like a web app > > reload, that's a different matter entirely, of course. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "The Java Posse" group. To post to this group, send email to javaposse@googlegroups.com To unsubscribe from this group, send email to javaposse+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/javaposse?hl=en -~----------~----~----~----~------~----~------~--~---
