Just add few cents to Stuart superb answer: the singleton scope depends on the "realm" (no idea how to call it better) where it is singleton, as the "lifespan" of realm may not be same/aligned. Core and Core Extension lifespan vs Mojo/Plugin lifespan is clearly not the same...
Also, take a peek at maven classloading here http://takari.io/book/91-maven-classloading.html On Fri, Feb 5, 2021 at 10:40 AM Matthieu Brouillard <matth...@brouillard.fr> wrote: > Thank you Stuart for the detailed reply. > > On Fri, Feb 5, 2021 at 12:02 AM Stuart McCulloch <mccu...@gmail.com> > wrote: > > > Here's a quick patch that does the split: > > https://gist.github.com/mcculls/d22f01b0e380fdd9f9e2ac1e1bba7dd0 > > > > With these changes I get the following output: > > > > mvn validate > > [INFO] extension generated information: Build started at 1612479700634 > > [INFO] Scanning for projects... > > [INFO] > > [INFO] > > ------------------------------------------------------------------------ > > [INFO] Building maven demo 0 > > [INFO] > > ------------------------------------------------------------------------ > > [INFO] > > [INFO] --- maven-demo-mojo:0:info (demo) @ maven-demo --- > > [INFO] Information: Build started at 1612479700634 > > [INFO] > > ------------------------------------------------------------------------ > > [INFO] BUILD SUCCESS > > [INFO] > > ------------------------------------------------------------------------ > > [INFO] Total time: 0.108 s > > [INFO] Finished at: 2021-02-04T23:01:40Z > > [INFO] Final Memory: 9M/309M > > [INFO] > > ------------------------------------------------------------------------ > > > > > > On Thu, 4 Feb 2021 at 22:46, Stuart McCulloch <mccu...@gmail.com> wrote: > > > > > Yes it's down to classloading - the extension and plugin have different > > > classloaders and the InfoHolder class loaded by the extension is > > different > > > to the one loaded by the plugin. They may share the same name and have > > the > > > same original bytecode, but they were defined by different > classloaders. > > > You can see this by adding a constructor to InfoHolder and printing out > > its > > > classloader (you can also print the class' hashcode to show it really > is > > a > > > different class, just with the same name.) > > > > > > To share the extension class with the plugin you'll need to add an > > > extension descriptor to the jar: > > > > > > https://maven.apache.org/ref/3.6.0/maven-core/extension.html > > > > > > But you'll also need to solve a second issue which comes down to the > fact > > > you're using the same jar as an extension and a plugin - the component > > > metadata is going to be registered in both places, which will still > lead > > to > > > two separate copies (each component will be a singleton in its own > > 'realm' > > > governed by the component metadata.) > > > > > > I would recommend using two separate projects - one for the extension > and > > > one for the plugin. The extension project will have the component and > > > the extension descriptor, while the plugin project will just have the > > mojo > > > and depend on the extension project. > > > > > > > > > On Thu, 4 Feb 2021 at 20:40, Matthieu Brouillard < > matth...@brouillard.fr > > > > > > wrote: > > > > > >> Hum some words have disappeared from my previous mail. > > >> The project URL is https://github.com/McFoggy/maven-jsr330-demo > > >> <https://github.com/McFoggy/maven-jsr330-demoYou>. > > >> And the corrected sentence is: You will see that the project is > > simple... > > >> Sorry for the double post. > > >> > > >> > > >> On Thu, Feb 4, 2021 at 9:27 PM Matthieu Brouillard < > > >> matth...@brouillard.fr> > > >> wrote: > > >> > > >> > Hi all, > > >> > > > >> > As I was trying to cleanup & simplify my plugins by moving to > JSR330, > > I > > >> > came across a weird use case in which a `@Singleton` object exists > > >> multiple > > >> > times (several instances) during the build: > > >> > - it is first used by an extension, to store some value > > >> > - then used in a mojo to retrieve and print the value > > >> > > > >> > Before opening an issue, I wanted to be sure that I did not make > some > > >> > errors in the simplified project and that my expectations of how it > > >> should > > >> > work are OK. > > >> > > > >> > I pushed a simplified project with README here: > > >> > https://github.com/McFoggy/maven-jsr330-demoYou will that the > project > > >> is > > >> > simple: > > >> > - the @Singleton information store > > >> > - the extension filling the store > > >> > - the mojo > > >> > > > >> > Thanks for any enlightenment. > > >> > > > >> > PS: can the issue come from different classloaders being probably > > used? > > >> > > > >> > Matthieu > > >> > > > >> > > > > > >
