How can I create an executable JAR with dependencies using Maven? – Dev

The best answers to the question “How can I create an executable JAR with dependencies using Maven?” in the category Dev.

QUESTION:

I want to package my project in a single executable JAR for distribution.

How can I make a Maven project package all dependency JARs into my output JAR?

ANSWER:

You can use the dependency-plugin to generate all dependencies in a separate directory before the package phase and then include that in the classpath of the manifest:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-dependency-plugin</artifactId>
    <executions>
        <execution>
            <id>copy-dependencies</id>
            <phase>prepare-package</phase>
            <goals>
                <goal>copy-dependencies</goal>
            </goals>
            <configuration>
                <outputDirectory>${project.build.directory}/lib</outputDirectory>
                <overWriteReleases>false</overWriteReleases>
                <overWriteSnapshots>false</overWriteSnapshots>
                <overWriteIfNewer>true</overWriteIfNewer>
            </configuration>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <configuration>
        <archive>
            <manifest>
                <addClasspath>true</addClasspath>
                <classpathPrefix>lib/</classpathPrefix>
                <mainClass>theMainClass</mainClass>
            </manifest>
        </archive>
    </configuration>
</plugin>

Alternatively use ${project.build.directory}/classes/lib as OutputDirectory to integrate all jar-files into the main jar, but then you will need to add custom classloading code to load the jars.

ANSWER:

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

and you run it with

mvn clean compile assembly:single

Compile goal should be added before assembly:single or otherwise the code on your own project is not included.

See more details in comments.


Commonly this goal is tied to a build phase to execute automatically. This ensures the JAR is built when executing mvn install or performing a deployment/release.

<plugin>
  <artifactId>maven-assembly-plugin</artifactId>
  <configuration>
    <archive>
      <manifest>
        <mainClass>fully.qualified.MainClass</mainClass>
      </manifest>
    </archive>
    <descriptorRefs>
      <descriptorRef>jar-with-dependencies</descriptorRef>
    </descriptorRefs>
  </configuration>
  <executions>
    <execution>
      <id>make-assembly</id> <!-- this is used for inheritance merges -->
      <phase>package</phase> <!-- bind to the packaging phase -->
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
</plugin>

ANSWER:

Taking Unanswered’s answer and reformatting it, we have:

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

Next, I would recommend making this a natural part of your build, rather than something to call explicitly. To make this a integral part of your build, add this plugin to your pom.xml and bind it to the package lifecycle event. However, a gotcha is that you need to call the assembly:single goal if putting this in your pom.xml, while you would call ‘assembly:assembly’ if executing it manually from the command line.

<project>
  [...]
  <build>
      <plugins>
          <plugin>
              <artifactId>maven-assembly-plugin</artifactId>
              <configuration>
                  <archive>
                      <manifest>
                          <addClasspath>true</addClasspath>
                          <mainClass>fully.qualified.MainClass</mainClass>
                      </manifest>
                  </archive>
                  <descriptorRefs>
                      <descriptorRef>jar-with-dependencies</descriptorRef>
                  </descriptorRefs>
              </configuration>
              <executions>
                  <execution>
                      <id>make-my-jar-with-dependencies</id>
                      <phase>package</phase>
                      <goals>
                          <goal>single</goal>
                      </goals>
                  </execution>
              </executions>
          </plugin>
      [...]
      </plugins>
    [...]
  </build>
</project>

ANSWER:

See executable-jar-with-maven-example (GitHub)

Notes

Those pros and cons are provided by Stephan.


For Manual Deployment

  • Pros
  • Cons
    • Dependencies are out of the final jar.

Copy Dependencies to a specific directory

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-dependency-plugin</artifactId>
  <executions>
    <execution>
      <id>copy-dependencies</id>
      <phase>prepare-package</phase>
      <goals>
        <goal>copy-dependencies</goal>
      </goals>
      <configuration>
        <outputDirectory>${project.build.directory}/${project.build.finalName}.lib</outputDirectory>
      </configuration>
    </execution>
  </executions>
</plugin>

Make the Jar Executable and Classpath Aware

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-jar-plugin</artifactId>
  <configuration>
    <archive>
      <manifest>
        <addClasspath>true</addClasspath>
        <classpathPrefix>${project.build.finalName}.lib/</classpathPrefix>
        <mainClass>${fully.qualified.main.class}</mainClass>
      </manifest>
    </archive>
  </configuration>
</plugin>

At this point the jar is actually executable with external classpath elements.

$ java -jar target/${project.build.finalName}.jar

Make Deployable Archives

The jar file is only executable with the sibling ...lib/ directory. We need to make archives to deploy with the directory and its content.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-antrun-plugin</artifactId>
  <executions>
    <execution>
      <id>antrun-archive</id>
      <phase>package</phase>
      <goals>
        <goal>run</goal>
      </goals>
      <configuration>
        <target>
          <property name="final.name" value="${project.build.directory}/${project.build.finalName}"/>
          <property name="archive.includes" value="${project.build.finalName}.${project.packaging} ${project.build.finalName}.lib/*"/>
          <property name="tar.destfile" value="${final.name}.tar"/>
          <zip basedir="${project.build.directory}" destfile="${final.name}.zip" includes="${archive.includes}" />
          <tar basedir="${project.build.directory}" destfile="${tar.destfile}" includes="${archive.includes}" />
          <gzip src="${tar.destfile}" destfile="${tar.destfile}.gz" />
          <bzip2 src="${tar.destfile}" destfile="${tar.destfile}.bz2" />
        </target>
      </configuration>
    </execution>
  </executions>
</plugin>

Now you have target/${project.build.finalName}.(zip|tar|tar.bz2|tar.gz) which each contains the jar and lib/*.


Apache Maven Assembly Plugin

  • Pros
  • Cons
    • No class relocation support (use maven-shade-plugin if class relocation is needed).
<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-assembly-plugin</artifactId>
  <executions>
    <execution>
      <phase>package</phase>
      <goals>
        <goal>single</goal>
      </goals>
      <configuration>
        <archive>
          <manifest>
            <mainClass>${fully.qualified.main.class}</mainClass>
          </manifest>
        </archive>
        <descriptorRefs>
          <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
      </configuration>
    </execution>
  </executions>
</plugin>

You have target/${project.bulid.finalName}-jar-with-dependencies.jar.


Apache Maven Shade Plugin

  • Pros
  • Cons
<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-shade-plugin</artifactId>
  <executions>
    <execution>
      <goals>
        <goal>shade</goal>
      </goals>
      <configuration>
        <shadedArtifactAttached>true</shadedArtifactAttached>
        <transformers>
          <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
            <mainClass>${fully.qualified.main.class}</mainClass>
          </transformer>
        </transformers>
      </configuration>
    </execution>
  </executions>
</plugin>

You have target/${project.build.finalName}-shaded.jar.


onejar-maven-plugin

  • Pros
  • Cons
    • Not actively supported since 2012.
<plugin>
  <!--groupId>org.dstovall</groupId--> <!-- not available on the central -->
  <groupId>com.jolira</groupId>
  <artifactId>onejar-maven-plugin</artifactId>
  <executions>
    <execution>
      <configuration>
        <mainClass>${fully.qualified.main.class}</mainClass>
        <attachToBuild>true</attachToBuild>
        <!-- https://code.google.com/p/onejar-maven-plugin/issues/detail?id=8 -->
        <!--classifier>onejar</classifier-->
        <filename>${project.build.finalName}-onejar.${project.packaging}</filename>
      </configuration>
      <goals>
        <goal>one-jar</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Spring Boot Maven Plugin

  • Pros
  • Cons
    • Add potential unecessary Spring and Spring Boot related classes.
<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <executions>
    <execution>
      <goals>
        <goal>repackage</goal>
      </goals>
      <configuration>
        <classifier>spring-boot</classifier>
        <mainClass>${fully.qualified.main.class}</mainClass>
      </configuration>
    </execution>
  </executions>
</plugin>

You have target/${project.bulid.finalName}-spring-boot.jar.