Extract required libraries using maven assembly plugin

I have a maven project that works fine so far, but building an executable JAR gives me a problem I could not solve so far.

This question here: Why is my .jar file running slower than the program in eclipse?

faces my problem and the method „Extract required libraries into generated jar“ seems to be the solution but i can not find anything how to do this using maven.

Currently I am using the maven assembly plugin but the resulting jar needs ages to start. Starting via IntelliJ needs seconds.

Any advice how to this right? Thx in advance.

The standard executable JAR in Java is only meta information in META-INF/MANIFEST.MF

1. Main-Class - main class
2. Class-Path - full list with all dependencies (could be with relative paths)

With Maven I usually create it in 3 steps:

1. using maven-dependency-plugin prepare runtime-dependencies

<plugin>
    <artifact>maven-dependency-plugin</artifact>
    <executions>
        <execution>
            <id>prepare-libs</id>
            <goals>
                <goal>copy-dependencies</goal>  
            </goals>
            <configuration>
                <outputDirectory>${project.build.directory}/libs</outputDirectory> <!-- generate folder target/libs with all external JARs -->
                <includeScope>runtime</includeScope>
            </configuration>
        </execution>
    </executions>
</plugin>

2. create jar with correct META-INF/MANIFEST.MF using maven-jar-plugin

<plugin>
    <artifact>maven-jar-plugin</artifact>
    <configuration>     
        <addClasspath>true</addClasspath>
        <classpathPrefix>libs/</classpathPrefix>
        <mainClass>org.super.MySuperMainClass</mainClass> <!-- sure it should be you real mian class -->
    </configuration>
</plugin>

3. assemble these libs and main JAR in the ZIP file using maven-assembly-plugin

<plugin>
    <artifact>maven-assembly-plugin</artifact>
    <configuration>     
        <descriptors>
            <descriptor>${project.basedir}/src/assembly/full.xml</descriptor>
        </descriptors>
    </configuration>
    <executions>
        <execution>
            <id>make-full-zip</id>
            <phase>package</phase>
            <goals>
                <goal>single</goal> 
            </goals>
        </execution>
    </executions>
</plugin>

full.xml:

<?xml version="1.0" encoding="UTF-8"?>
<assembly xmlns="http://maven.apache.org/ASSEMBLY/2.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/ASSEMBLY/2.0.0 http://maven.apache.org/xsd/assembly-2.0.0.xsd">

    <id>full</id><!-- will be end part of target file name -->

    <formats>
        <format>zip</format>
    </formats>

    <baseDirectory>/</baseDirectory>

    <fileSets>

        <fileSet>
            <directory>${project.build.directory}/libs</directory>
            <filtered>false</filtered>
            <outputDirectory>./libs</outputDirectory>
        </fileSet>

    </fileSets>

    <files>
        <file>
            <source>${project.build.directory}/${project.artifactId}-${project.version}.jar</source>
            <filtered>false</filtered>
            <outputDirectory>./</outputDirectory>
        </file> 
    </files>

</assembly>

As a result of maven build, you will receive a ZIP file (in /target folder) containing your "main" JAR and all dependencies that it requires at runtime. You can expand it in any folder and start it with "java -jar ...".

P.S. ZIP is a standard Maven artifact, so this ZIP is deployed without any additional movements to the repository (Nexus or Artifactory or etc.). And so, you can simply integrate it into a CD process that creates a Docker container with your application, for example.