Multiple Versions at Launch-Time

[Nicolai Parlog]

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 Hi Eric.

> Why not use OSGi? Or is that what you mean by a "container"?
I assume that the quote I gave uses "container" to mean systems like
OSGi (it's from Alan, maybe he will correct me if I'm wrong). So yes,
I mean that.

I am trying to find a way without OSGi because it looks like it is not
used for many projects (relatively speaking). But most projects
routinely run into problems with conflicting versions and it would be
great if Jigsaw could solve this for them out of the box.

 so long ... Nicolai



On 20.10.2015 18:10, Eric Johnson wrote:
> Why not use OSGi? Or is that what you mean by a "container"?
> 
> Eric.
> 
> On Tue, Oct 20, 2015 at 6:30 AM, Nicolai Parlog <nipa at codefx.org>
> wrote:
> 
> Hi!
> 
> There have been a number of threads regarding loading multiple 
> versions of the same module. The requirements say:
> 
> "It is not necessary to support more than one version of a module 
> within a single configuration."[1]
> 
> The threads hence usually end like this:
> 
> "The module system isn't suggesting any solutions, it is instead 
> leaving this problem to the build tools and containers."[2]
> 
> I can see how we can use class loaders (and now layers) to load 
> multiple versions at runtime. This is essentially what containers
> do.
> 
> Now I wonder, is there anything a build tool (or a dedicated
> developer for that matter) can do to launch the JVM with multiple
> versions of the same module?
> 
> Running Example:
> 
> App requires LibA App requires LibB version 2 LibA requires LibB
> version 1
> 
> One way I hoped to do this was to treat both versions as two
> different modules, i.e. renaming them and update the dependencies
> on them.
> 
> App requires LibA App requires LibB_v2 LibA requires LibB_v1
> 
> This does not work because both modules would export the same 
> packages. That's a little disappointing - I hoped it wouldn't
> matter because no module is reading from both versions.
> 
> Since this failed I see no way to solve this aspect of JAR hell 
> without containers. Does anybody else seen one?
> 
> so long ... Nicolai
> 
> 
> [1]
> http://openjdk.java.net/projects/jigsaw/spec/reqs/#multiple-versions
>
> 
[2]
> http://mail.openjdk.java.net/pipermail/jigsaw-dev/2015-October/004787.
ht
>
> 
ml
> 
> 
> 
>> 
>> 
> 

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