Question

I am trying to run my first Java program, an example script that interacts with a online API (source on Github).

As it has dependencies, I follow the recommended steps using mvn test and mvn package, which seem to work (see output).

I however do not understand how to run the program that I just compiled (or packaged?). The .java file contains public final class NesstarStudyLister, so based on the pom.xml file I try (in the base directory) the following command:

mhermans@fyr:~/tmp/nesstar-api-demo$ java -cp target/nesstar_study_lister-1.0-SNAPSHOT.jar com.nesstar.demo.NesstarStudyLister

Which results in a NoClassDefFoundError.

How can I successfully run the small Java-program?

EDIT:

Based on the recommendation of Dave Newton, I used the Exec Maven plugin, which apparently simply consists of running

mvn exec:java -Dexec.mainClass=com.nesstar.demo.NesstarStudyLister

in the base directory, which flawlessly executes the java program.

The solution by Andriy Plokhotnyuk also works, using these commands:

(edit pom.xml to include the <build>...</build> information)
mvn package
java -jar target/nesstar_study_lister-1.0-SNAPSHOT-jar-with-dependencies.jar

Answer 1

The easiest way is generally the Exec Maven Plugin.

Nutshell:

• Add the exec plugin as a dependency.
• Define the main class attribute (your program’s entry point).
• Run the exec goal.

You may also use Maven to create a directory with your project’s dependencies (jars) and set the classpath manually, but IMO that’s kind of a pain when you can use the plugin.

You may also create a jar that includes all your project’s dependencies in a single file, but this may require a bit more work to explicitly include/exclude any conflicting dependencies. (With the caveat that this may be an issue with either other method as well.)