How to Fix \"NoClassDefFoundError\" on Maven Dependency When Running from Command Line?

How to Fix "NoClassDefFoundError on Maven Dependency"

When attempting to run a Maven project from the command line, you may encounter the NoClassDefFoundError, indicating that a required dependency is missing.

The main reason for this error is that Maven doesn't automatically include dependencies in the JAR file it builds. To resolve this, you need to "shade" the library code into your output JAR file.

To achieve this, you can use the maven-shade-plugin. Here's how to add it to your POM:

<code class="xml"><project>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.5.2</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  ...
</project></code>

This plugin will automatically create an "uber-JAR" containing your classes and the library dependencies.

Once the plugin is registered, you can run the following commands:

<code class="sh">$ mvn package
$ java -cp target/bil138_4-0.0.1-SNAPSHOT.jar tr.edu.hacettepe.cs.b21127113.bil138_4.App</code>

If the error persists, you can further configure the shade plugin to specify which JARs should be included, or to set a Main-Class for an executable JAR file. Refer to the maven-shade-plugin documentation for more information.

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