Groovy is a dynamic language based on the Java Virtual Machine which compiles to Java bytecode. Groovy is a project in the Codehaus community. If you are fluent in Java, Groovy will seem like a natural choice for a scripting language. Groovy takes the features of Java, pares down the syntax a bit, and adds features like closures, duck-typing, and regular expressions. For more information about Groovy, please see the Groovy web site at http://groovy.codehaus.org.
To create a Maven Plugin using Groovy, you only need two files: a
pom.xml and a single Mojo implemented in Groovy. To
get started, create a project directory named
firstgroovy-maven-plugin. Place the following
pom.xml in this directory.
Example 18.9. POM for a Groovy Maven Plugin
<?xml version="1.0" encoding="UTF-8"?>
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>org.sonatype.mavenbook.plugins</groupId>
<artifactId>firstgroovy-maven-plugin</artifactId>
<name>Example Groovy Mojo - firstgroovy-maven-plugin</name>
<packaging>maven-plugin</packaging>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.codehaus.mojo.groovy</groupId>
<artifactId>groovy-mojo-support</artifactId>
<version>1.0-beta-3</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-plugin-plugin</artifactId>
<version>2.3</version>
</plugin>
<plugin>
<groupId>org.codehaus.mojo.groovy</groupId>
<artifactId>groovy-maven-plugin</artifactId>
<version>1.0-beta-3</version>
<extensions>true</extensions>
<executions>
<execution>
<goals>
<goal>generateStubs</goal>
<goal>compile</goal>
<goal>generateTestStubs</goal>
<goal>testCompile</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
What's going on in this POM? First, notice that
the packaging of the POM is
maven-plugin because we are creating a project that
will package a Maven plugin. Next, note that the project depends on the
groovy-mojo-support artifact in the
org.codehaus.mojo.groovy group.
Then under src/main/groovy in a directory
org/sonatype/mavenbook/plugins, create a file named
EchoMojo.groovy which contains the EchoMojo
class.
Example 18.10.
package org.sonatype.mavenbook.plugins
import org.codehaus.mojo.groovy.GroovyMojo
/**
* Example goal which echos a message
*
* @goal echo
*/
class EchoMojo extends GroovyMojo {
/**
* Message to print
*
* @parameter expression="${echo.message}"
* default-value="Hello Maven World"
*/
String message
void execute() {
log.info( message )
}
}