Singleton component

[di...@buschmais.com]

Hi,

during the developing a Maven plugin (Maven project API version 3.0.5) for
the project jQAssistant (jqassistant.org) and I'm running into an issue
where I need some help:

The plugin mojo scans the artifacts generated by the build process
(classes, etc.) into an embedded instance of the graph database Neo4j to
provide the base for further analysis. As starting and shutting down the
database instance is quite expensive I would like to re-use a cached
instance for multi-module projects.

I'm trying to hold this instance in singleton class:

@org.codehaus.plexus.component.annotations.Component(role =
StoreProvider.class, instantiationStrategy = "singleton")
public class StoreProvider implements Disposable {
...
}

and inject it into my Mojo using

@org.apache.maven.plugins.annotations.Component;
private StoreProvider storeProvider;

For several project structures I can see that multiple instances of the
singleton are created which breaks the contract I was hoping I could
establish (the database complains that there's already a running
instance).

It seems that this bevahior is related to the presence of some specific
plugins in the multi-module project to be scanned:

<groupId>org.codehaus.sonar</groupId>
<artifactId>sonar-packaging-maven-plugin</artifactId>
<version>1.9</version>
<extensions>true</extensions>

How can I solve this problem?

Thanks in advance,

Dirk


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Re: Singleton component

[Dan Tran <da...@gmail.com>]

http://maven.40175.n5.nabble.com/problem-Maven-creates-the-second-plugin-classloader-during-parallel-build-and-uses-two-classloader-hy-td5713793.html


https://cwiki.apache.org/confluence/display/MAVEN/Maven+3.x+Class+Loading

May help

-d
On Tuesday, July 29, 2014, <di...@buschmais.com> wrote:

> Hi,
>
> during the developing a Maven plugin (Maven project API version 3.0.5) for
> the project jQAssistant (jqassistant.org) and I'm running into an issue
> where I need some help:
>
> The plugin mojo scans the artifacts generated by the build process
> (classes, etc.) into an embedded instance of the graph database Neo4j to
> provide the base for further analysis. As starting and shutting down the
> database instance is quite expensive I would like to re-use a cached
> instance for multi-module projects.
>
> I'm trying to hold this instance in singleton class:
>
> @org.codehaus.plexus.component.annotations.Component(role =
> StoreProvider.class, instantiationStrategy = "singleton")
> public class StoreProvider implements Disposable {
> ...
> }
>
> and inject it into my Mojo using
>
> @org.apache.maven.plugins.annotations.Component;
> private StoreProvider storeProvider;
>
> For several project structures I can see that multiple instances of the
> singleton are created which breaks the contract I was hoping I could
> establish (the database complains that there's already a running
> instance).
>
> It seems that this bevahior is related to the presence of some specific
> plugins in the multi-module project to be scanned:
>
> <groupId>org.codehaus.sonar</groupId>
> <artifactId>sonar-packaging-maven-plugin</artifactId>
> <version>1.9</version>
> <extensions>true</extensions>
>
> How can I solve this problem?
>
> Thanks in advance,
>
> Dirk
>
>
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> To unsubscribe, e-mail: dev-unsubscribe@maven.apache.org <javascript:;>
> For additional commands, e-mail: dev-help@maven.apache.org <javascript:;>
>
>