I am trying to follow the tutorial in Chapter 7 in this online book: <http://books.sonatype.com/mvnex-book/reference/index.html>

This tutorial is intended to demonstrate a web application with Spring Framework with hibernate, and I am stuck here：

mvn hibernate3:hbm2ddl

```
...
<build>
    <finalName>simple-webapp</finalName>
    <plugins>
        <plugin>
                <groupId>org.mortbay.jetty</groupId>
                <artifactId>maven-jetty-plugin</artifactId>
                <dependencies>
                        <dependency>
                            <groupId>hsqldb</groupId>
                            <artifactId>hsqldb</artifactId>
                            <version>1.8.0.7</version>
                        </dependency>
                </dependencies>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
                <artifactId>hibernate3-maven-plugin</artifactId>
                <version>2.0</version>
                <configuration>
                    <components>
                        <component>
                            <name>hbm2ddl</name>
                            <implementation>annotationconfiguration</implementation>
                        </component>
                    </components>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>hsqldb</groupId>
                        <artifactId>hsqldb</artifactId>
                        <version>1.8.0.7</version>
                    </dependency>
                    <dependency>
                <groupId>org.hibernate.javax.persistence</groupId>
                <artifactId>hibernate-jpa-2.0-api</artifactId>
                <version>1.0.0.Final</version>
            </dependency>
            <dependency>
                <groupId>org.hibernate</groupId>
                <artifactId>hibernate-entitymanager</artifactId>
                <version>3.6.7.Final</version>
            </dependency>
                </dependencies>
        </plugin>
    </plugins>
</build>

```

The error message is below. Any insight or pointer will be appreciated. Thanks.

```
@localhost simple-webapp]$ mvn hibernate3:hbm2ddl
[INFO] Scanning for projects...
[WARNING] 
[WARNING] Some problems were encountered while building the effective model for     org.sonatype.mavenbook.multispring:simple-webapp:war:1.0
[WARNING] 'build.plugins.plugin.version' for org.mortbay.jetty:maven-jetty-plugin is     missing. @ org.sonatype.mavenbook.multispring:simple-webapp:[unknown-version],     /home/abigail/workspace/simple-parent/simple-webapp/pom.xml, line 46, column 21
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-    plugin is missing. @ org.sonatype.mavenbook.multispring:simple-parent:1.0,     /home/abigail/workspace/simple-parent/pom.xml, line 29, column 12
[WARNING] 
[WARNING] It is highly recommended to fix these problems because they threaten the     stability of your build. 
[WARNING] 
[WARNING] For this reason, future Maven versions might no longer support building such     malformed projects.
[WARNING] 
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building Simple Web Application 1.0
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] >>> hibernate3-maven-plugin:3.0:hbm2ddl (default-cli) > compile @ simple-webapp     >>>
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ simple-webapp ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e.     build is platform dependent!
[INFO] skip non existing resourceDirectory /home/abigail/workspace/simple-parent/simple-    webapp/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ simple-webapp ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] <<< hibernate3-maven-plugin:3.0:hbm2ddl (default-cli) < compile @ simple-webapp     <<<
[INFO] 
[INFO] --- hibernate3-maven-plugin:3.0:hbm2ddl (default-cli) @ simple-webapp ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.959 s
[INFO] Finished at: 2014-09-03T02:35:24-04:00
[INFO] Final Memory: 12M/208M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:hibernate3-maven-plugin:3.0:hbm2ddl     (default-cli) on project simple-webapp: There was an error creating the AntRun task.     NullPointerException -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[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

```