Building a fat jar using maven

I have a code base which I want to distribute as jar. It also have dependency on external jars, which I want to bundle in the final jar.

I heard that this can be done using maven-assembly-plug-in, but I don't understand how. Could someone point me to some examples.

Right now, I'm using fat jar to bundle the final jar. I want to achieve the same thing using maven.

Solution 1:

Note: If you are a spring-boot application, read the end of answer

Add following plugin to your pom.xml The latest version can be found at

...
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>CHOOSE LATEST VERSION HERE</version>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
            </configuration>
            <executions>
                <execution>
                    <id>assemble-all</id>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
...

After configuring this plug-in, running mvn package will produce two jars: one containing just the project classes, and a second fat jar with all dependencies with the suffix "-jar-with-dependencies".

if you want correct classpath setup at runtime then also add following plugin

<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>

For spring boot application use just following plugin (choose appropriate version of it)

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <fork>true</fork>
        <mainClass>${start-class}</mainClass>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>repackage</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Solution 2:

You can use the maven-shade-plugin.

After configuring the shade plugin in your build the command mvn package will create one single jar with all dependencies merged into it.

Solution 3:

Maybe you want maven-shade-plugin, bundle dependencies, minimize unused code and hide external dependencies to avoid conflicts.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.1.1</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <minimizeJar>true</minimizeJar>
                        <createDependencyReducedPom>true</createDependencyReducedPom>
                        <dependencyReducedPomLocation>
                            ${java.io.tmpdir}/dependency-reduced-pom.xml
                        </dependencyReducedPomLocation>
                        <relocations>
                            <relocation>
                                <pattern>com.acme.coyote</pattern>
                                <shadedPattern>hidden.coyote</shadedPattern>
                            </relocation>
                        </relocations>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

References:

• http://maven.apache.org/plugins/maven-shade-plugin/plugin-info.html
• http://maven.apache.org/plugins/maven-shade-plugin/shade-mojo.html

Solution 4:

actually, adding the

<archive>
   <manifest>
    <addClasspath>true</addClasspath>
    <packageName>com.some.pkg</packageName>                     
    <mainClass>com.MainClass</mainClass>
  </manifest>
</archive>

declaration to maven-jar-plugin does not add the main class entry to the manifest file for me. I had to add it to the maven-assembly-plugin in order to get that in the manifest