Can maven exec:java be used with an arbitrary java class from the command iine - maven

Question

We have a few java/scala classes with main methods that would be useful to run via mvn exec:java.
Is it possible to do so without specifying the classes in the pom.xml? The examples that I have seen look like this:
<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>some.main.MyClass</mainClass>
</configuration>
</plugin>
And then get executed as:
mvn exec:java -Dexec.mainClass="some.main.MyClass"
The intent is to be able to run
mvn exec:java -Dexec.mainClass="some.other.main.OtherClass"
even though it were not specified in the pom.xml.
When attempting to run that the error is
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.6.0:java (default-cli) on project sentiment: An exception occured while executing the Java class. myapp.MyMain
In other words the class specified on the command line is ignored in favor of the one listed in the pom.xml.

Answer 1

The Documentation at https://www.mojohaus.org/exec-maven-plugin/usage.html
says:
If you want to execute Java programs in the same VM, you can either
use the command line version
mvn exec:java -Dexec.mainClass="com.example.Main" [-Dexec.args="argument1"]
This works without adding anything to your pom.
As written in the comment, this only works, if you don't have a configuration in your pom. If you do have a configuration in your pom, you can use a property in it, which can be overridden from the command line
<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>${my.mainClass}</mainClass>
</configuration>
</plugin>
and predefine the property (nested directly in <project>)
<properties>
<my.mainClass>some.main.MyClass</my.mainClass>
</properties>
then you can run with
mvn exec:java -Dmy.mainClass="aaa.Test"

Answer 2

Looking from your usage if you are using the -Dexec.mainClass everytime, i would suggest you can get rid of the mainClass in the plugin configuration. The benefit of defining the mainClass would be to run like : mvn exec:java & it picks the main class from your defined class in pom.xml.
Once you remove the mainClass from pom.xml, you should be able to use any mainClass in the maven exec plugin usage from command line.