Create a fat Jar file – Maven Assembly Plugin

In this tutorial, we will show you how to create a fat/uber jar with Maven Assembly Plugin. Which means create a Jar together with its dependency Jars into a single executable Jar file.

Note
Maven assembly plugin is not good in producing fat/uber jar, it may cause name conflict issue, it is better to use other Maven plugins like :

1 – Maven shade plugin solve this by using technique like class relocating.

2 – Maven one-jar plugin, add the dependency jar file directly into project jar, and loads it with custom class loader.

1. Review a Java project

Previous Java project (dateutils) will be reused, see following folder structure

Note

This project has a single dependency – joda-time.jar

2. Pom.xml

Read below comment for self-explanatory.

pom.xml

<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/maven-v4_0_0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.favtuts.core.utils</groupId>
	<artifactId>dateUtils</artifactId>
	<packaging>jar</packaging>
	<version>1.0-SNAPSHOT</version>
	<name>dateUtils</name>
	<url>http://maven.apache.org</url>

	<properties>
		<jdk.version>1.7</jdk.version>
		<jodatime.version>2.5</jodatime.version>
		<junit.version>4.11</junit.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>${junit.version}</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>joda-time</groupId>
			<artifactId>joda-time</artifactId>
			<version>${jodatime.version}</version>
		</dependency>
	</dependencies>

	<build>
		<finalName>dateutils</finalName>
		<plugins>

			<!-- download source code in Eclipse, best practice -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-eclipse-plugin</artifactId>
				<version>2.9</version>
				<configuration>
					<downloadSources>true</downloadSources>
					<downloadJavadocs>false</downloadJavadocs>
				</configuration>
			</plugin>

			<!-- Set a compiler level -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>2.3.2</version>
				<configuration>
					<source>${jdk.version}</source>
					<target>${jdk.version}</target>
				</configuration>
			</plugin>

			<!-- Maven Assembly Plugin -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-assembly-plugin</artifactId>
				<version>2.4.1</version>
				<configuration>
					<!-- get all project dependencies -->
					<descriptorRefs>
						<descriptorRef>jar-with-dependencies</descriptorRef>
					</descriptorRefs>
					<!-- MainClass in mainfest make a executable jar -->
					<archive>
					  <manifest>
						<mainClass>com.favtuts.core.utils.App</mainClass>
					  </manifest>
					</archive>

				</configuration>
				<executions>
				  <execution>
					<id>make-assembly</id>
                                        <!-- bind to the packaging phase -->
					<phase>package</phase> 
					<goals>
						<goal>single</goal>
					</goals>
				  </execution>
				</executions>
			</plugin>

		</plugins>
	</build>

</project>

3. Package It

Above “Maven Assembly Plugin” is bind to the Maven’s packaging phase, to produces the final Jar, just package it :

$ mvn package

[INFO] 
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ dateUtils ---
[INFO] Building jar: /Users/favtuts/dateUtils/target/dateutils.jar
[INFO] 
[INFO] --- maven-assembly-plugin:2.4.1:single (make-assembly) @ dateUtils ---
[INFO] Building jar: /Users/favtuts/dateUtils/target/dateutils-jar-with-dependencies.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.325s
[INFO] Finished at: Tue Oct 21 13:44:41 MYT 2014
[INFO] Final Memory: 17M/42M
[INFO] ------------------------------------------------------------------------

Two jar files will be created in the target folder.

1. dateutils.jar – Only your project classes
2. dateutils-jar-with-dependencies.jar – Project and dependency classes in a single jar.

4. Review It

List out the content of dateutils-jar-with-dependencies.jar

$ jar tf target/dateutils-jar-with-dependencies.jar 

META-INF/
META-INF/MANIFEST.MF
org/
org/joda/
org/joda/time/
org/joda/time/base/
org/joda/time/chrono/
org/joda/time/tz/ZoneInfoCompiler$DateTimeOfYear.class
org/joda/time/tz/ZoneInfoCompiler$Rule.class
org/joda/time/tz/ZoneInfoCompiler$RuleSet.class
org/joda/time/tz/ZoneInfoCompiler$Zone.class
org/joda/time/tz/ZoneInfoCompiler.class
org/joda/time/tz/ZoneInfoProvider.class
org/joda/time/UTCDateTimeZone.class
org/joda/time/Weeks.class
org/joda/time/YearMonth$Property.class
org/joda/time/YearMonth.class
org/joda/time/YearMonthDay$Property.class
org/joda/time/YearMonthDay.class
org/joda/time/Years.class
META-INF/maven/
META-INF/maven/joda-time/
META-INF/maven/joda-time/joda-time/
META-INF/maven/joda-time/joda-time/pom.xml
META-INF/maven/joda-time/joda-time/pom.properties
com/
com/favtuts/
com/favtuts/core/
com/favtuts/core/utils/
com/favtuts/core/utils/App.class
META-INF/maven/com.favtuts.core.utils/
META-INF/maven/com.favtuts.core.utils/dateUtils/
META-INF/maven/com.favtuts.core.utils/dateUtils/pom.xml
META-INF/maven/com.favtuts.core.utils/dateUtils/pom.properties

MANIFEST.MF

Manifest-Version: 1.0
Built-By: favtuts
Build-Jdk: 1.7.0_05
Created-By: Apache Maven 3.1.1
Main-Class: com.favtuts.core.utils.App
Archiver-Version: Plexus Archiver

Run it

$ java -jar target/dateutils-jar-with-dependencies.jar 

2014-10-21

Download Source Code

$ git clone https://github.com/favtuts/java-maven-tutorials.git
$ cd maven-assembly-plugin/dateUtils

$ mvn clean package

$ java -jar dateutils-jar-with-dependencies.jar

References

1. Apache Maven Assembly Plugin
2. Create A Fat Jar File – Maven One-JAR Example
3. Maven shade plugin
4. How to create a jar file with Maven