Maven by example - NullPointer executing hibernate3:hbm2ddl

Question

I am following the Maven by example guide to learn Maven.

I am busy working through chapter 7, which is a simple multimodule enterprise project containing spring and hibernate. The example files for this chapter can be downloaded here, in the ch-multi-spring directory.

Sections 7.1 to 7.6 talk about the specifics of each module. In section 7, the database is generated and the application is run. It is at this step that I receive the following error:

> mvn hibernate3:hbm2ddl -X
<Some output left out>
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] Multi-Spring Chapter Simple Parent Project ........ FAILURE [0.752s]
[INFO] Multi-Spring Chapter Simple Object Model .......... SKIPPED
[INFO] Multi-Spring Chapter Simple Weather API ........... SKIPPED
[INFO] Multi-Spring Chapter Simple Persistence API ....... SKIPPED
[INFO] Multi-Spring Chapter Simple Command Line Tool ..... SKIPPED
[INFO] Multi-Spring Chapter Simple Web Application ....... SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.330s
[INFO] Finished at: Thu Apr 24 15:31:18 CEST 2014
[INFO] Final Memory: 9M/154M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:hibernate3-maven-plugin:3.0:hbm2ddl (default-cli) on project simple-parent: There was an error creating the AntRun task. NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:hibernate3-maven-plugin:3.0:hbm2ddl (default-cli) on project simple-parent: There was an error creating the AntRun task.
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:317)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:152)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:555)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:214)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:158)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.MojoExecutionException: There was an error creating the AntRun task.
    at org.codehaus.mojo.hibernate3.AbstractHibernateMojo.execute(AbstractHibernateMojo.java:84)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:106)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
    ... 19 more
Caused by: java.lang.NullPointerException
    at org.codehaus.plexus.configuration.DefaultPlexusConfiguration.add(DefaultPlexusConfiguration.java:175)
    at org.codehaus.plexus.configuration.DefaultPlexusConfiguration.addChild(DefaultPlexusConfiguration.java:151)
    at org.codehaus.mojo.hibernate3.util.PlexusConfigurationUtils.setHibernateConfiguration(PlexusConfigurationUtils.java:289)
    at org.codehaus.mojo.hibernate3.util.PlexusConfigurationUtils.parseHibernateTool(PlexusConfigurationUtils.java:67)
    at org.codehaus.mojo.hibernate3.AbstractHibernateToolMojo.getConfiguration(AbstractHibernateToolMojo.java:60)
    at org.codehaus.mojo.hibernate3.AbstractHibernateMojo.execute(AbstractHibernateMojo.java:76)
    ... 21 more
[ERROR] 
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

Since I'm still learning Maven, and not familiar with Hibernate, I have no idea what the problem could be. I haven't changed anything in the downloaded example files.

Answer 1

I figured out the answer.

Here is the summary of my findings:

• the mvn hibernate3:hbm2ddl command should be run from the simple-webapp or simple-command folder. (The specification for the plugin should be present in the POM for that module.)
• increasing the hibernate3-maven-plugin version to 3.0 will reintroduce the problem, I believe I read some posts that the configuration format had been changed, but I didn't look further into it.
• the mvn hibernate3:hbm2ddl will report the error shown below if JAVA_HOME is set to JDK1.7 instead of 1.6 (Found solution to this here)

org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:hibernate3-maven-plugin:2.1:hbm2ddl (default-cli) on project simple-command: Could not get ConfigurationTask.

Answer 2

I was getting the same error. I modified the version number of hibernate3-maven-plugin plugin:

<groupId>org.codehaus.mojo</groupId>
  <artifactId>hibernate3-maven-plugin</artifactId>
  <!-- insted of 2.1 as documented inside the Maven by example guide -->
  <version>2.2</version>  
  ....  
</groupId>

And this fixed the issue. Moreover, I'm using JDK 1.8. Below the 'mvn -v' output:

Java version: 1.8.0_20, vendor: Oracle Corporation
Java home: C:\Program Files\Java\jdk1.8.0_20\jre
Default locale: en_US, platform encoding: Cp1252
OS name: "windows 7", version: "6.1", arch: "amd64", family: "dos"