[FIXED] no main manifest in maven jar

Issue

I've build this project with mvn clean install. Now I have a .jar file but I'm not able to use it with:

λ java -jar flyway-commandline-xxx.jar
no main manifest attribute, in flyway-commandline-xxx.jar

What am I missing?

Solution

An executable jar needs a "manifest file" - which is located at META-INF/MANIFEST.MF inside the jar.

You can use the Maven Assembly plugin to produce this manifest file in line with this:

...
<plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>2.5.5</version>
    <configuration>
        <archive>
            <manifest>
                <mainClass>dk.tbsalling.ais.cli.AisCli</mainClass>
            </manifest>
        </archive>
        <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
    </configuration>
    <executions>
        <execution>
            <id>make-assembly</id>
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
</plugin>
...

The MainClass (referenced in the manifest file) is the class containing the main(...)-method called when you execute the jar.

You can have a look at https://github.com/tbsalling/aiscli/blob/master/pom.xml for a full, working example.

Answered By - tbsalling
Answer Checked By - Gilberto Lyons (JavaFixing Admin)