Cannot execute Groovy Maven Plugin as a goal

Question

I am using Apache Maven 3.3.9 with the Groovy Maven plugin. Here is the relevant section of the pom.xml (the inlined Groovy script is just fictional):

<plugin>
    <groupId>org.codehaus.gmaven</groupId>
    <artifactId>groovy-maven-plugin</artifactId>
    <version>2.0</version>
    <executions>
      <execution>
        <id>myGroovyPlugin</id>
        <phase>prepare-package</phase>
        <goals>
          <goal>execute</goal>
        </goals>
        <configuration>
          <source>
    log.info('Test message: {}', 'Hello, World!')
          </source>
        </configuration>
      </execution>
    </executions>
</plugin>

If I am calling mvn install the inline Groovy script gets called by the plugin as part of the prepare-package phase and works just fine. But if I try to call the plugins' goal directly via mvn groovy:execute I get the following error message:

[ERROR] Failed to execute goal org.codehaus.gmaven:groovy-maven-plugin:2.0:execute (default-cli) on project exercise02: The parameters 'source' for goal org.codehaus.gmaven:groovy-maven-plugin:2.0:execute are missing or invalid -> [Help 1]

Answer 1

The error you are getting is already pointing at the issue: the plugin couldn't not find the source configuration option because indeed it is only configured within the myGroovyPlugin execution, that is, only in the execution scope and not as a global configuration.

This is the main difference between configuration element outside the executions (global configuration for all executions of the plugin (even from command line) and within an execution (configuration only applied to that particular goal execution).

To fix the issue you should move the configuration element outside the executions section in this case, since the plugin is not a plugin invoked during default bindings by Maven, it would be enough and not have impact on your build: it will be still used during the myGroovyPlugin execution AND from explicit executions from command line.

From Maven POM reference, the configuration within an execution:

confines the configuration to this specific list of goals, rather than all goals under the plugin.

---

To make it clear, you should change it to the following:

<plugin>
    <groupId>org.codehaus.gmaven</groupId>
    <artifactId>groovy-maven-plugin</artifactId>
    <version>2.0</version>
    <executions>
      <execution>
        <id>myGroovyPlugin</id>
        <phase>prepare-package</phase>
        <goals>
          <goal>execute</goal>
        </goals>
      </execution>
    </executions>
    <configuration>
      <source>log.info('Test message: {}', 'Hello, World!')</source>
    </configuration>        
</plugin>

As such the configuration will become a global configuration and applied to both command line executions and declared executions.

---

Since you are using Maven 3.3.9, you could also make use of a slightly more verbose pattern to invoke directly a specific configuration of an execution:

mvn groovy:execute@myGroovyPlugin

This pattern is useful in cases where you really don't want a global configuration because you don't want to impact other (often default) executions of a certain plugin and you really want to use a specific isolated configuration both in an execution and from command line.