Groovy and Maven: Stuck in compiling and testing a very simple - maven

Question

I am stuck trying to compile and test a extremely simple project. It's a beginner project in order to understand how all of this works, and I am currently stucked.
My main objective is to understand how to handle resources files that are located outside of the standard folder structure.
I have a main class, with two methods. One load a resource file which is on the standard folder structure (src\main\resources). Another one load a resource which is in a custom folder, outside of the standard structure (resources).
There is one junit file that simply verify that the resource is correctly loaded.
It works fine with IntelliJ. I simply declared the resources folder as resources folders and that's it.
Now with maven ..... actually I can't even compile with gmaven-plus. Nor run the test. So I did not even bother to declare the custom folder as a resource in the pom.xml file.
I based my pom.xml file based on an existing pom we have at work and from stuff I read on the web. There's no way I can make it work.
Here is a link to a 7zip file with my project, if one could put me on the right track, I would be grateful.
https://www.dropbox.com/s/jvn32ll5xfvjfwd/GroovyExample.7z?dl=0
Here is the pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>groupId</groupId>
<artifactId>Example</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-all</artifactId>
<version>2.4.13</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter</artifactId>
<version>5.4.0</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.gmavenplus</groupId>
<artifactId>gmavenplus-plugin</artifactId>
<version>1.8.1</version>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>compileTests</goal>
</goals>
<configuration>
<sources>
<source>
<directory>src/main/groovy</directory>
<includes>
<include>**/*.groovy</include>
</includes>
</source>
</sources>
<testSources>
<testSource>
<directory>src/test/groovy</directory>
<includes>
<include>**/*.groovy</include>
</includes>
</testSource>
</testSources>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>3.0.0-M1</version>
<configuration>
<failIfNoTests>true</failIfNoTests>
<testSourceDirectory>str/test/</testSourceDirectory>
<includes>
<include>**/*Test*.*</include>
</includes>
</configuration>
</plugin>
</plugins>
</build>
</project>
Here is the output:
Unable to get Groovy version from InvokerHelper or GroovySystem,
trying jar name.
Failed to execute goal
org.codehaus.gmavenplus:gmavenplus-plugin:1.8.1:compile (default) on
project Example: Execution default of goal
org.codehaus.gmavenplus:gmavenplus-plugin:1.8.1:compile failed.

Answer 1

The 2.4 groovy-all POMs do not include Groovy as a dependency, because they are a POM for an uber-jar, rather than a POM that describes all the Groovy module jars. Because of this, GMavenPlus is unable to find the Groovy jar to use for compilation. The <type>pom</type> works for Groovy 2.5, and 3.0, but not 2.4. So for your use case, simply delete the <type>pom</type> (or replace it with the default of <type>jar</type>). This was the way Groovy was often included back before 2.5, so the groovy-all POMs of 2.5 and 3.0 were added to ease the transition. See https://groovy-lang.org/releasenotes/groovy-2.5.html#Groovy2.5releasenotes-Packaging.