How to create a manifest file with Maven

This tutorial will show you how to use the maven-jar-plugin to create a manifest file, and package / add it into the final jar file. The manifest file is normally used to define following tasks :

1. Define the entry point of the Application, make the Jar executable.
2. Add project dependency classpath.

When you run the command mvn package to package project into a Jar, the following meta-inf/manifest.mf file will be generated and added into the final Jar file automatically.

Manifest-Version: 1.0
Built-By: ${user.name}
Build-Jdk: ${java.version}
Created-By: Apache Maven
Archiver-Version: Plexus Archiver

1. Make the Jar executable

Define maven-jar-plugin in pom.xml, and configure the manifest file via configuration tag.

    <plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-jar-plugin</artifactId>
	<version>2.4</version>
	<configuration>
	  <archive>
	    <manifest>
		<mainClass>com.mkyong.core.App</mainClass>
	    </manifest>
	  </archive>
	</configuration>
    </plugin>

Following manifest file will be generated. If you run this Jar, it will execute the com.mkyong.core.App.

anifest-Version: 1.0
Built-By: mkyong
Build-Jdk: 1.6.0_35
Created-By: Apache Maven
Main-Class: com.mkyong.core.App
Archiver-Version: Plexus Archiver

2. Add project dependency classpath.

Most Java projects need dependency, and it can define in manifest file easily. Normally, you will use maven-dependency-plugin to copy project dependencies to somewhere else.

  <plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-jar-plugin</artifactId>
	<version>2.4</version>
	<configuration>
	  <archive>
	    <manifest>
		<addClasspath>true</addClasspath>
		<mainClass>com.mkyong.core.App</mainClass>
		<classpathPrefix>dependency-jars/</classpathPrefix>
	    </manifest>
	  </archive>
	</configuration>
  </plugin>
  <plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-dependency-plugin</artifactId>
	<version>2.5.1</version>
	<executions>
	  <execution>
		<id>copy-dependencies</id>
		<phase>package</phase>
		<goals>
		    <goal>copy-dependencies</goal>
		</goals>
		<configuration>
		    <outputDirectory>
                          ${project.build.directory}/dependency-jars/
                    </outputDirectory>
		</configuration>
	    </execution>
	</executions>
  </plugin>

Following manifest file will be generated. The project dependencies will be copied to {project}/target/dependency-jars/.

manifest-Version: 1.0
Built-By: mkyong
Build-Jdk: 1.6.0_35
Class-Path: dependency-jars/log4j-1.2.17.jar
Created-By: Apache Maven
Main-Class: com.mkyong.core.App
Archiver-Version: Plexus Archiver

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References

1. Maven manifest references
2. Maven manifest examples
3. How to create a Jar file with Maven