Wednesday, 22 September 2010

Use maven 3 apis in a hudson plugin

Using maven 3 apis in a hudson needs to change classLoader hierarchy as hudson load some old maven artifacts in the parent classLoader.
So the solution is to use a child first classLoader.
This new classLoader has been introduced in hudson 1.378. (see HUDSON-5360).
So you can now use it to made your plugin dependencies win on hudson core classLoader.
Some steps are needed.
Configuring your hpi plugin

<plugin>
<groupid>org.jvnet.hudson.tools</groupid>
<artifactid>maven-hpi-plugin</artifactid>
<version>1.54</version>
<configuration>
<pluginFirstClassLoader>true</pluginFirstClassLoader>
</configuration>
</plugin>

So now your pluginWrapper.classLoader will be of type PluginFirstClassLoader.

// pluginId is project.artifactId from your plugin pom
PluginWrapper pluginWrapper = Hudson.getInstance().getPluginManager().getPlugin( pluginId );
PluginFirstClassLoader pluginFirstClassLoader = (PluginFirstClassLoader) pluginWrapper.classLoader;


Now everthing is ready but some other tricks are needed :-)

Create a PlexusContainer (note you must use the new "plexus-guice" bridge).
This means you need the following dependency :

<dependency>
<groupId>org.sonatype.sisu</groupId>
<artifactId>sisu-inject-plexus</artifactId>
<version>1.4.1</version>
</dependency>

And very important you must exclude dependencies from the original plexus-container

<dependency>
<groupId>org.sonatype.aether</groupId>
<artifactId>aether-connector-wagon</artifactId>
<version>${aetherVersion}</version>
<exclusions>
<exclusion>
<groupId>org.codehaus.plexus</groupId>
<artifactId>plexus-container-default</artifactId>
</exclusion>
</exclusions>
</dependency>


To prevent this you can add an enforcer rule which will chech plexus-container-default inclusion

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.0-beta-1</version>
<executions>
<execution>
<goals>
<goal>enforce</goal>
</goals>
<phase>validate</phase>
<id>ensure-no-plexus-container</id>
<configuration>
<rules>
<bannedDependencies>
<excludes>
<exclude>org.codehaus.plexus:plexus-container-default</exclude>
</excludes>
<message>
ensure-no-plexus-container doesn't work anymore with maven 3 librairies. you have to add some exclusions.
</message>
</bannedDependencies>
</rules>
<fail>true</fail>
</configuration>
</execution>
</executions>
</plugin>


How to create the PlexusContainer from the PluginFirstClassLoader :

private PlexusContainer getPlexusContainer(PluginFirstClassLoader pluginFirstClassLoader) throws PlexusContainerException {
DefaultContainerConfiguration conf = new DefaultContainerConfiguration();
ClassWorld world = new ClassWorld();
ClassRealm classRealm = new ClassRealm( world, "project-building", pluginFirstClassLoader );
// olamy yup hackish but it's needed for plexus-shim which needs a URLClassLoader and PluginFirstClassLoader is not
for ( URL url : pluginFirstClassLoader.getURLs() )
{
classRealm.addURL( url );
LOGGER.fine( "add url " + url.toExternalForm() );
}
conf.setRealm( classRealm );

return new DefaultPlexusContainer( conf );
}


Then set the current Thread classLoader (don't miss to restore the original one in a finally statement

PlexusContainer plexusContainer = getPlexusContainer( pluginFirstClassLoader );

Thread.currentThread().setContextClassLoader( plexusContainer.getContainerRealm() );


Now you can play with maven 3 apis

ProjectBuilder projectBuilder = plexusContainer.lookup( ProjectBuilder.class );


A first sample is the plugin called : maven-dependency-update-trigger
: sources and Wiki Page (under construction :-) )
You must have a look at the dependencies used.

The plugin will check your project according to a cron expression and schedule a build if a snapshot dependency has changed (dependency and plugin).

It will be released as son as hudson 1.378 will be released.

Note : hpi:run doesn't work yet for this plugin as it needs some changes in the hpi mojo to handle the new PluginFirstClassLoader.

4 comments:

nicolas deloof said...

Joli boulot Olivier. Si avec ça on a pas un Hudson Maven3-compliant sous peu, je ne sais pas ce qu'il faudra faire

abayer1138 said...

Olivier, you are awesome. =)

arham said...

Hi Oliver,

Just wanted to confirm if I got the things right.
Does this plugin check the repository provided in the settings.xml to figure out whether the dependent snapshot has been updated or not??
The Snapshot ultimately gets deployed into the repository with a timestamp as suffix. Will this plugin take care of that even or I'll have to deploy the Snapshot with no timestamp but as it is.

olamy said...

Hi Arham,
Yes usual maven settings are used (repositories in settings and in poms).
Use timestamped version it's always better.