src/it/projects/mojo-configuration/manifest-with-mainClass/pom.xml

<project xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd' xmlns='http://maven.apache.org/POM/4.0.0'>
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <groupId>org.apache.maven.plugin.assembly.test</groupId>
    <artifactId>it-project-parent</artifactId>
    <version>1</version>
  </parent>
  
  <groupId>test</groupId>
  <artifactId>manifest-with-mainClass</artifactId>
  <packaging>jar</packaging>
  <version>1</version>
  <name>Maven Quick Start Archetype</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <executions>
          <execution>
            <id>assembly</id>
            <phase>package</phase>
            <goals>
              <goal>single</goal>
            </goals>
            <configuration>
              <descriptorRefs>
                <descriptorRef>jar-with-dependencies</descriptorRef>
              </descriptorRefs>
              <archive>
                <manifest>
                  <mainClass>test.App</mainClass>
                </manifest>
              </archive>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>