I want to create a single executable jar file including its dependency. I want the dependency to be stored under lib/ as jar files, the main app itself is unpacked at the top level of the jar. When executing the jar file however, it throws me a NoClassDefFoundError when trying to instantiate an object from the dependency.

When the dependency is unpacked at the top level of the jar file, everything works like a charm. But, as mentioned above the dependency should be stored as separate jar file under lib/

Any ideas what is missing here? 🧐

POM File:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>jo.vpl</groupId>
    <artifactId>VPL-Core-Hubs</artifactId>
    <version>1</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>${project.groupId}</groupId>
            <artifactId>jo.vpl</artifactId>
            <version>2</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.7</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>21</maven.compiler.source>
        <maven.compiler.target>21</maven.compiler.target>
    </properties>

    <build>
        <finalName>VPL-Core-Hubs</finalName>
        <plugins>   
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>jo.vpl.hub.Main</mainClass>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>lib/</classpathPrefix>
                        </manifest>
                    </archive>
                    <descriptors>
                        <descriptor>${basedir}/assembly.xml</descriptor>      
                    </descriptors>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>             
        </plugins>        
    </build>
</project>

Assembly.xml

<assembly  
    xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">  
    <id>jar-with-dependencies</id>  
    <formats>  
        <format>jar</format>  
    </formats>  
    <includeBaseDirectory>false</includeBaseDirectory>  
    <dependencySets>  
        <dependencySet>  
            <unpack>true</unpack>
            <useProjectArtifact>true</useProjectArtifact>  
            <outputDirectory>/</outputDirectory>  
            <includes>  
                <include>jo.vpl:VPL-Core-Hubs</include>    
            </includes>  
        </dependencySet> 
        <dependencySet>  
            <unpack>false</unpack>
            <useProjectArtifact>true</useProjectArtifact>  
            <outputDirectory>lib/</outputDirectory>  
            <includes>  
                <include>com.google.code.gson:gson</include>    
            </includes>  
        </dependencySet>  
    </dependencySets>  
</assembly>