How to Package Java Projects into a Clean JAR with a Separate lib Directory Using Maven

Goal

In many Java deployments we prefer not to bundle all classes and dependencies into a single fat JAR. Instead we want the project's own classes in a clean xxx.jar and third‑party libraries placed under a lib/ sub‑directory for easier management, replacement, and multi‑environment deployment.

Demo Project Setup

A new Maven project is created to illustrate the approach. The main class com.anfioo.Main is written (see the screenshot below).

Adding a Third‑Party Dependency

Gson is added as an example external library.

POM Configuration

The pom.xml is configured with two plugins:

maven-jar-plugin – sets the final jar name, defines the main class in the manifest, and directs the output to ${project.build.directory}/output.

maven-dependency-plugin – copies all runtime dependencies into ${project.build.directory}/output/lib, creating the desired lib/ folder.

<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>com.anfioo</groupId>
    <artifactId>module-admin</artifactId>
    <version>1.0.0</version>
    <build>
        <finalName>module-admin</finalName>
        <plugins>
            <!-- Make the JAR aware of the main class -->
            <plugin>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.2.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>com.anfioo.Main</mainClass>
                        </manifest>
                    </archive>
                    <outputDirectory>${project.build.directory}/output</outputDirectory>
                </configuration>
            </plugin>
            <!-- Copy dependencies to lib directory -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>3.1.2</version>
                <executions>
                    <execution>
                        <id>copy-dependencies</id>
                        <phase>package</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${project.build.directory}/output/lib</outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    <dependencies>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.10.1</version>
        </dependency>
    </dependencies>
</project>

Build and Run

Execute the Maven build: mvn clean package The build produces module-admin.jar and a lib/ directory containing the copied dependencies (see screenshot).

Run the application with the classpath pointing to both the jar and the lib folder:

java -cp "module-admin.jar;lib/*" com.anfioo.Main

The program starts correctly, confirming that the modular packaging works as intended.