Building a runnable jar with Maven 2

Question

I'm relatively new to the Maven mantra, but I'm trying to build a command-line runnable jar with Maven. I've setup my dependencies, but when I run mvn install and attempt to run the jar, two things happen. First, no main class is found, which is correctable. When I've corrected this, I get errors on run stating that classes cannot be found.

Maven is not packaging my dependency libraries inside of the jar, so I am unable to run the jar as a stand-alone application. How do I correct this?

Maybe this one stackoverflow.com/questions/1832853/…, or this one stackoverflow.com/questions/574594/… (but the accepted answer is wrong), or this one stackoverflow.com/questions/1814526/…. Actually, this seems to be one of the most frequent question on maven... — Pascal Thivent
– Pascal Thivent, Commented Jan 7, 2010 at 18:00
The other answers aren't as clean, and uber jar (ueber spelled incorrectly), does not mention executability. Furthermore, the other topics are littered with irrelevant material, such as source level etc. — Stefan Kendall
– Stefan Kendall, Commented Jan 7, 2010 at 18:21
possible duplicate of Is it possible to package all the jar dependencies in one big jar? — ataylor
– ataylor, Commented Dec 8, 2011 at 16:20
I see many of the answers are ~10 years old, so I would be interested to see if there is anything different now. — Aaron Kurtzhals
– Aaron Kurtzhals, Commented Sep 23, 2022 at 14:44

Adrian Petrescu · Accepted Answer · 2011-09-20 05:00:10Z

The easiest way to do this would be to create an assembly using the maven-assembly-plugin and the predefined jar-with-dependencies descriptor. You'll also need to generate a manifest with a main-class entry for this uber jar. The snippet below shows how to configure the assembly plugin to do so:

<build> <plugins> <plugin> <artifactId>maven-assembly-plugin</artifactId> <configuration> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> <archive> <manifest> <mainClass>fully.qualified.MainClass</mainClass> </manifest> </archive> </configuration> </plugin> </plugins> </build>

Then, to generate the assembly, just run:

mvn assembly:assembly

If you want to generate the assembly as part of your build, simply bind the assembly:single mojo to the package phase:

<build> <plugins> <plugin> <artifactId>maven-assembly-plugin</artifactId> <configuration> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> <archive> <manifest> <mainClass>fully.qualified.MainClass</mainClass> </manifest> </archive> </configuration> <executions> <execution> <phase>package</phase> <goals> <goal>single</goal> </goals> </execution> </executions> </plugin> </plugins> </build>

And simply run:

mvn package

The maven-shade-plugin also works similarly and is dedicated to this purpose.
This does not work for spring, and other libraries that expect multiple resources with the same name on the class path. In the case of spring, META-INF\spring.schemas is included in several jars (beans, jdbc, etc) and is used to configure XML namespace support for the XML parser. If you try 'jar-with-dependencies', pasing application-context.xml will fail at runtime with something like "org.xml.sax.SAXParseException: cvc-elt.1: Cannot find the declaration of element 'beans'."
@David Maven won't solve a Java "limitation". Just package your application cleanly (i.e. not in a uberjar) in that case.
This works with Spring configuration with no issues. My main class loads all other classes with Classpath Application context and this solution works perfectly.

Joachim Sauer · Accepted Answer · 2012-09-05 09:20:22Z

Maven is not packaging your dependencies inside your jar file, because you don't usually do this with Java programs.

Instead you deliver the dependencies together with your jar file and mention them in the Class-Path header of the Manifest.

To go this route, you'll need to enable the addClasspath property (documented here) for the maven-jar-plugin.

If you really want to include all your dependencies in your jar file, then you can use the Maven Assembly plugin to create a jar-with-dependencies.

+1 I've had a hard time finding information on how java programs are typically intended to be built and distributed, especially with Maven.

user2409824 · Accepted Answer · 2013-08-05 13:30:20Z

8

This is what I would do for small projects. Most of the time you don't want one huge jar.

to build: mvn clean dependency:copy-dependencies package

to execute (in target dir): java -cp myjar.jar:./dependency/* com.something.MyClass

answered Aug 5, 2013 at 13:30

user2409824

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2 Comments

Roboprog Over a year ago

Great! I saved this in my Makefile, in the same directory with pom.xml. build:\n mvn .... (what you said)

Shekhar Over a year ago

Thanks. After searching internet for more than 2 hours found this very useful answer....

formixian · Accepted Answer · 2012-03-15 14:44:08Z

I Agree with Joachim Sauer,

Instead of using jar-with-dependency you should configure the jar plugin like that in your pom.xml:

<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-jar-plugin</artifactId> <version>2.4</version> <configuration> <archive> <index>true</index> <manifest> <addClasspath>true</addClasspath> <mainClass>[mainClassFullName]</mainClass> </manifest> <manifestEntries> <mode>development</mode> <url>${project.url}</url> <key>value</key> </manifestEntries> </archive> </configuration> </plugin>

And use this assembly configuration to add the jar dependencies to you assembly:

<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>zip-with-jars</id> <formats> <format>zip</format> </formats> <includeBaseDirectory>false</includeBaseDirectory> <dependencySets> <dependencySets> <dependencySet> <outputDirectory>/</outputDirectory> <useProjectArtifact>true</useProjectArtifact> <unpack>false</unpack> <scope>runtime</scope> </dependencySet> </dependencySets> </dependencySets> </assembly>

likeGreen · Accepted Answer · 2014-07-29 23:11:47Z

Just add the below code in pom.xml and Run as: maven:install . The jar will be created in target folder of eclipse which can be used as "java -jar Hello.jar" . but make sure that name of main class is given com.abc.HelloWorld.java

<build> <plugins> <plugin> <groupid>org.apache.maven.plugins</groupid> <artifactid>maven-shade-plugin</artifactid> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> <configuration> <finalname>HelloW</finalname> <transformers> <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"> <manifestentries> <main-class>com.abc.HelloWorld.java</main-class> <build-number>1</build-number> </manifestentries> </transformer> </transformers> </configuration> </execution> </executions> </plugin> </plugins> </build>

Aaron Kurtzhals · Accepted Answer · 2022-09-23 14:44:02Z

I have a spring boot application, and the jar created by maven package can be run without setting up additional plugins.

Inside my pom.xml:

<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.6.12</version> <relativePath/> <!-- lookup parent from repository --> </parent>

https://spring.io/projects/spring-boot

ElSaeed · Accepted Answer · 2024-03-01 18:49:51Z

To package your dependencies inside the JAR so that it can be run as a standalone application, you need to configure the Maven Assembly Plugin or the Maven Shade Plugin. Here's how you can do it using the Maven Shade Plugin:

First, add the Maven Shade Plugin to your pom.xml file inside the section:

<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-shade-plugin</artifactId> <version>3.2.4</version> <!-- Or use the latest version --> <executions> <execution> <phase>package</phase> <goals> <goal>shade</goal> </goals> <configuration> <transformers> <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"> <mainClass>org.mapReduce.WordCountRunner</mainClass> <!-- Update with your main class --> </transformer> </transformers> </configuration> </execution> </executions> </plugin>

Replace org.mapReduce.WordCountRunner with the fully qualified name of your main class.
After adding the plugin configuration, run mvn clean package to create the shaded JAR.

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