Using project dependencies' sources

This is pretty similar to the Copying project dependencies or Unpacking project dependencies examples.

Instead of using the project dependencies it uses their sources. Use the goal copy-dependencies to just copy the sources jars to a directory or unpack-dependencies to extract them. See the sample below:

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>3.11.0</version>
        <executions>
          <execution>
            <id>src-dependencies</id>
            <phase>package</phase>
            <goals>
              <!-- use copy-dependencies instead if you don't want to explode the sources -->
              <goal>unpack-dependencies</goal>
            </goals>
            <configuration>
              <classifier>sources</classifier>
              <failOnMissingClassifierArtifact>false</failOnMissingClassifierArtifact>
              <outputDirectory>${project.build.directory}/sources</outputDirectory>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  [...]
</project>