Maven Shade Plugin – UberJar / Fat Jar Example

In this example, we will learn to use Maven Shade plugin to package a java project along with its dependencies into a fat jar or uber jar.

Maven Shade Plugin Syntax

Let’s go through basic syntax of maven shade plugin before learning how to use it in your project.

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-shade-plugin</artifactId>
	<version>2.4.3</version>
	<executions>
	  <execution>
	    <phase>package</phase>
	    <goals>
	      	<goal>shade</goal>
	    </goals>
	    <configuration>
	      	<transformers>
		        <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
		          	<manifestEntries>
		            	<Main-Class>com.howtodoinjava.demo.App</Main-Class>
		            	<Build-Number>1.0</Build-Number>
		          	</manifestEntries>
		        </transformer>
	      	</transformers>
	    </configuration>
	  </execution>
	</executions>
</plugin>

1. <goal>shade</goal> tells that it should be run in package phase.
2. ManifestResourceTransformer creates the entries in MANIFEST.MF file as key-value pairs in the <manifestEntries>.
3. You can use more available transfers as per your need.

Sample Maven Project

Let’s create a sample maven project and add some dependencies into it. This is the pom.xml file for it.

<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.howtodoinjava.demo</groupId>
	<artifactId>MavenShadeExample</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>MavenShadeExample</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.17</version>
		</dependency>
		<dependency>
			<groupId>org.apache.commons</groupId>
			<artifactId>commons-lang3</artifactId>
			<version>3.4</version>
		</dependency>
	</dependencies>

	<build>
		<finalName>MavenShadeExample-uber</finalName>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-shade-plugin</artifactId>
				<version>2.4.3</version>
				<executions>
					<execution>
						<phase>package</phase>
						<goals>
							<goal>shade</goal>
						</goals>
						<configuration>
							<transformers>
								<transformer
									implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
									<manifestEntries>
										<Main-Class>com.howtodoinjava.demo.App</Main-Class>
										<Build-Number>1.0</Build-Number>
									</manifestEntries>
								</transformer>
							</transformers>
						</configuration>
					</execution>
				</executions>
			</plugin>
		</plugins>
	</build>
</project>

Project structure looks like this.

Run Maven Package Goal

> mvn package

When you run the package goal in project’s root directory, you will get two generated jar files i.e. and one extra pom.xml file named with dependency-reduced-pom.xml.

1. MavenShadeExample-uber.jar : This is fat/uber jar with all dependencies inside it.
2. dependency-reduced-pom.xml : This generated maven file is your pom.xml file minus all dependencies.
3. original-MavenShadeExample-uber.jar : This jar has been generated by executing dependency-reduced-pom.xml.

Verify all classes in generated by running below command.

jar -tvf MavenShadeExample-uber.jar

Output will be listed in command prompt with all classes inside it.

Manifest file content could also be verified.

Manifest-Version: 1.0
Build-Number: 1.0
Build-Jdk: 1.6.0_33
Created-By: Apache Maven
Main-Class: com.howtodoinjava.demo.App

Drop me your questions in comments section.

Happy Learning !!