Al ejecutar la creación de un instalador, ya sea mediante la opción mvn create installer o mediante un comando similar a este desde la consola:

mvn -P create-installer install

es habitual encontrarse con un error que termina con líneas como estas:

[artifact:mvn] [INFO] Creating package of the package info:
[artifact:mvn] [INFO] org.gvsig.installer.lib.impl.DefaultPackageInfo@11e8050 (
[artifact:mvn]        code: org.gvsig.oracle
[artifact:mvn]        name: 
[artifact:mvn]        description: 
[artifact:mvn]        gvSIG-version: 
[artifact:mvn]        version: 0.0.1-0
[artifact:mvn]        buildNumber: 0
[artifact:mvn]        operating-system: all
[artifact:mvn]        architecture: all
[artifact:mvn]        java-version: j1_5
[artifact:mvn]        download-url: 
[artifact:mvn]        state: devel
[artifact:mvn]        official: false
[artifact:mvn]        type: unknow
[artifact:mvn]        model-version: 1.0.1
[artifact:mvn]        owner: 
[artifact:mvn]        owner-url: 
[artifact:mvn]        sources-url: 
[artifact:mvn]        dependencies: 
[artifact:mvn]        web-url: 
[artifact:mvn]        categories: [])
[artifact:mvn] [INFO] ------------------------------------------------------------------------
[artifact:mvn] [ERROR] FATAL ERROR
[artifact:mvn] [INFO] ------------------------------------------------------------------------
[artifact:mvn] [INFO] null
[artifact:mvn] [INFO] ------------------------------------------------------------------------
[artifact:mvn] [INFO] Trace
[artifact:mvn] java.lang.NullPointerException
[artifact:mvn]        at java.util.Hashtable.put(Hashtable.java:394)
[artifact:mvn]        at java.util.Properties.setProperty(Properties.java:143)
[artifact:mvn]        at org.gvsig.installer.lib.impl.info.InstallerInfoFileWriter.write(InstallerInfoFileWriter.java:101)
[artifact:mvn]        at org.gvsig.installer.lib.impl.info.InstallerInfoFileWriter.write(InstallerInfoFileWriter.java:74)
[artifact:mvn]        at org.gvsig.installer.lib.impl.info.InstallerInfoFileWriter.write(InstallerInfoFileWriter.java:59)
[artifact:mvn]        at org.gvsig.installer.lib.impl.DefaultInstallerProviderServices.writePackageInfoFile(DefaultInstallerProviderServices.java:148)
[artifact:mvn]        at org.gvsig.installer.lib.impl.DefaultInstallerProviderServices.writePackageInfoForIndex(DefaultInstallerProviderServices.java:136)
[artifact:mvn]        at org.gvsig.installer.lib.impl.creation.DefaultMakePluginPackageService.writePackageInfoForIndex(DefaultMakePluginPackageService.java:221)
[artifact:mvn]        at org.gvsig.installer.maven.GeneratePluginPackageIndexMojo.createPackage(GeneratePluginPackageIndexMojo.java:83)
[artifact:mvn]        at org.gvsig.installer.maven.AbstractGeneratePackageMojo.execute(AbstractGeneratePackageMojo.java:167)
[artifact:mvn]        at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490)
[artifact:mvn]        at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694)
[artifact:mvn]        at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:556)
[artifact:mvn]        at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:535)
[artifact:mvn]        at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387)
[artifact:mvn]        at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:348)
[artifact:mvn]        at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180)
[artifact:mvn]        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)
[artifact:mvn]        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138)
[artifact:mvn]        at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
[artifact:mvn]        at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:60)
[artifact:mvn]        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[artifact:mvn]        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
[artifact:mvn]        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
[artifact:mvn]        at java.lang.reflect.Method.invoke(Method.java:597)
[artifact:mvn]        at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
[artifact:mvn]        at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
[artifact:mvn]        at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
[artifact:mvn]        at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
[artifact:mvn] [INFO] ------------------------------------------------------------------------
[artifact:mvn] [INFO] Total time: 11 seconds
[artifact:mvn] [INFO] Finished at: Fri May 11 15:34:48 CEST 2012
[artifact:mvn] [INFO] Final Memory: 57M/137M
[artifact:mvn] [INFO] ------------------------------------------------------------------------

BUILD FAILED
C:\dev\ew\gv2\build\ant-tasks\maven-goals.xml:35: The following error occurred while executing this line:
C:\dev\ew\gv2\build\ant-tasks\ant-tasks-config.xml:117: Java returned: 1

Esto suele ocurrir porque no se ha incluído una referencia al archivo package.info en distribution.xml. La solución consiste en añadir un párrafo similar a este en dicho archivo:

<assembly>
  ...
  <files>
  ...
      <file>
          <source>package.info</source>
          <outputDirectory>${extension.install.dir.name}
          </outputDirectory>
      </file>
  ...
  </files>    
  ...
</assembly>