GMaven: A Couple Early Problems Building a Plugin

My first attempt to build a Maven plugin using GMaven got off to a rough start. I don't want to use this space to complain by any means, but I would to share what I learned in case anyone else runs into something similar.

My first problem had to deal with my use of a newer version of GMaven:

      <plugin>
        <groupId>org.codehaus.gmaven</groupId>
        <artifactId>gmaven-plugin</artifactId>
        <version>1.3</version>
        <configuration>
          <providerSelection>1.7</providerSelection>
        </configuration>
        <extensions>true</extensions>
        <inherited>true</inherited>
        <executions>
          <execution>
            <goals>
              <goal>generateStubs</goal>
              <goal>compile</goal>
              <goal>generateTestStubs</goal>
              <goal>testCompile</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

During the build of the plugin, I was given a deprecation warning stating that no mojo descriptors were found in the project:

[WARNING] Deprecation Alert:
[WARNING] No mojo descriptors were found in this project which has a packaging type of maven-plugin.

I found that reason for the warning was that the stub generation was not retaining the Javadoc annotations used to mark a Mojo. By downgrading to version 1.2 of GMaven and changing the providerSelection to 1.6, the warning went away.

Next when trying to use the plugin in another build, I was present with something ilke:

This realm = plexus.core
urls[0] = file:/opt/apache-maven-2.2.1/lib/maven-2.2.1-uber.jar
Number of imports: 10
import: org.codehaus.classworlds.Entry@a6c57a42
import: org.codehaus.classworlds.Entry@12f43f3b
import: org.codehaus.classworlds.Entry@20025374
import: org.codehaus.classworlds.Entry@f8e44ca4
import: org.codehaus.classworlds.Entry@92758522
import: org.codehaus.classworlds.Entry@ebf2705b
import: org.codehaus.classworlds.Entry@bb25e54
import: org.codehaus.classworlds.Entry@bece5185
import: org.codehaus.classworlds.Entry@3fee8e37
import: org.codehaus.classworlds.Entry@3fee19d8
-----------------------------------------------------
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Internal error in the plugin manager executing goal 'org.prystasj.plugins:jms-testing:1.0-SNAPSHOT:hello': Unable to find the mojo 'hello' (or one of its required components) in the plugin 'org.prystasj.plugins:jms-testing'
org.codehaus.groovy.runtime.GroovyCategorySupport.getCategoryNameUsage(Ljava/lang/String;)Ljava/util/concurrent/atomic/AtomicInteger;

I found the solution to this problem was to exclude the groovy-all-minimal jar, version 1.5.7 with:

   <dependency>
      <groupId>org.codehaus.groovy.maven</groupId>
      <artifactId>gmaven-mojo</artifactId>
      <version>1.0</version>      
      <exclusions>
        <exclusion>
          <groupId>org.codehaus.groovy</groupId>
          <artifactId>groovy-all-minimal</artifactId>
        </exclusion>
      </exclusions>
    </dependency>

I also had another that was similar error related to class CallSiteArray that was alleviated by ensuring I was using Groovy 1.6 everywhere.