Building a fat jar using maven

Question

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.

Answer 1

An alternative is to use the maven shade plugin to build an uber-jar.

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version> Your Version Here </version>
    <configuration>
            <!-- put your configurations here -->
    </configuration>
    <executions>
            <execution>
                    <phase>package</phase>
                    <goals>
                            <goal>shade</goal>
                    </goals>
            </execution>
    </executions>
</plugin>

Answer 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.

Answer 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

Answer 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

Answer 5

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 https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-assembly-plugin

      ... 
      <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>

Answer 6

You can use the onejar-maven-plugin for packaging. Basically, it assembles your project and its dependencies in as one jar, including not just your project jar file, but also all external dependencies as a "jar of jars", e.g.

<build>
    <plugins>
        <plugin>
            <groupId>com.jolira</groupId>
            <artifactId>onejar-maven-plugin</artifactId>
                <version>1.4.4</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>one-jar</goal>
                        </goals>
                    </execution>
                </executions>
        </plugin>
    </plugins>
</build>

Note 1: Configuration options is available at the project home page.

Note 2: For one reason or the other, the onejar-maven-plugin project is not published at Maven Central. However jolira.com tracks the original project and publishes it to with the groupId com.jolira.