Plugin locks jar files

[wmarkow]

I have a build organized in the way that a webstart-maven-plugin is used to create a webstart distribution only. Jars are signed later by maven-jarsigner-plugin. By default maven-jarsigner-plugin tries to sign the main artifact as well but it fails because main jar file looks locked:

[DEBUG] Processing C:\workspace\sample\target\sample-0.0.1-SNAPSHOT.jar
[DEBUG] cmd.exe /X /C ""C:\Program Files\Java\jdk1.8.0_65\jre\..\bin\jarsigner.exe" -keystore C:\workspace\sample/etc/webstart/devstore.jks -storepass ***** C:\workspace\sample\target\sample-0.0.1-SNAPSHOT.jar dev"
[DEBUG] Executing: cmd.exe /X /C ""C:\Program Files\Java\jdk1.8.0_65\jre\..\bin\jarsigner.exe" -keystore C:\workspace\sample/etc/webstart/devstore.jks -storepass ***** C:\workspace\sample\target\sample-0.0.1-SNAPSHOT.jar dev"
[DEBUG] jarsigner: attempt to rename C:\workspace\sample\target\sample-0.0.1-SNAPSHOT.jar to C:\workspace\sample\target\sample-0.0.1-SNAPSHOT.jar.orig failed

I have track down that this lock is because of URLClassLoader instance created in org.codehaus.mojo.webstart.util.DefaultArtifactUtil.artifactContainsClass(Artifact, String) method.
This piece of code below fixes the problem but is Java 1.7+ specific:

@Override
public boolean artifactContainsClass( Artifact artifact, final String mainClass )
            throws MojoExecutionException
{
  ...
  URLClassLoader cl = new java.net.URLClassLoader( new URL[] { url } );
  ...
  // close the class loader
  try
  {
    cl.close();
  }
  catch( IOException e )
  {
    getLogger().warn( e.getMessage() );
  }
...
}

As a workaround I have configured the maven-jarsigner-plugin to not to sign the main artifact; it only signs the webstart distribution.

I'm using the 1.0-beta-7 version of the plugin. This version locks the jars. I have tested the 1.0.0-SNAPSHOT version as well which also locks the jars.