How do I execute a program using Maven?

Question

I would like to have a Maven goal trigger the execution of a java class. I'm trying to migrate over a Makefile with the lines:

neotest:
    mvn exec:java -Dexec.mainClass="org.dhappy.test.NeoTraverse"

And I would like mvn neotest to produce what make neotest does currently.

Neither the exec plugin documentation nor the Maven Ant tasks pages had any sort of straightforward example.

Currently, I'm at:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>exec-maven-plugin</artifactId>
  <version>1.1</version>
  <executions><execution>
    <goals><goal>java</goal></goals>
  </execution></executions>
  <configuration>
    <mainClass>org.dhappy.test.NeoTraverse</mainClass>
  </configuration>
</plugin>

I don't know how to trigger the plugin from the command line, though.

Answer 1

With the global configuration that you have defined for the exec-maven-plugin:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>exec-maven-plugin</artifactId>
  <version>1.1</version>
  <configuration>
    <mainClass>org.dhappy.test.NeoTraverse</mainClass>
  </configuration>
</plugin>

invoking mvn exec:java on the command line will invoke the plugin which is configured to execute the class org.dhappy.test.NeoTraverse.

So, to trigger the plugin from the command line, just run:

mvn exec:java

Now, if you want to execute the exec:java goal as part of your standard build, you'll need to bind the goal to a particular phase of the default lifecycle. To do this, declare the phase to which you want to bind the goal in the execution element:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>exec-maven-plugin</artifactId>
  <version>1.1</version>
  <executions>
    <execution>
      <id>my-execution</id>
      <phase>package</phase>
      <goals>
        <goal>java</goal>
      </goals>
    </execution>
  </executions>
  <configuration>
    <mainClass>org.dhappy.test.NeoTraverse</mainClass>
  </configuration>
</plugin>

With this example, your class would be executed during the package phase. This is just an example, adapt it to suit your needs.

Answer 2

In order to execute multiple programs, I also needed a profiles section:

<profiles><profile>
  <id>traverse</id>
  <activation><property><name>traverse</name></property></activation>
  <build><plugins><plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <configuration>
      <executable>java</executable>
      <arguments>
        <argument>-classpath</argument><classpath />
        <argument>org.dhappy.test.NeoTraverse</argument>
      </arguments>
    </configuration>
  </plugin></plugins></build>
</profile></profiles>

This is then executable as:

mvn exec:exec -Dtraverse