Preface

I recently started learning Java for upcoming projects. The best way to learn a language is to build something, so I created a Telegram bot and explored how Maven packages applications.

Fat vs. Thin JAR

• Fat JAR (Uber‑Jar): all classes and dependencies bundled into one large file—easy to deploy but big.
• Thin JAR: only compiled classes included; dependencies remain external, saving space at the cost of management complexity.

Project Setup

A project skeleton is generated with maven-archetype-quick. The structure resembles:

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telegram_bot
├── pom.xml
├── src/main/java/com/telegram_bot
│   ├── Main.java
│   └── Bot.java

Bot.java handles Telegram API interactions while Main.java launches the bot.

Packaging

Fat JAR with Maven Shade

Add the maven-shade-plugin to pom.xml to create a single executable JAR:

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<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-shade-plugin</artifactId>
  <version>3.5.0</version>
  <executions>
    <execution>
      <phase>package</phase>
      <goals><goal>shade</goal></goals>
      <configuration>
        <transformers>
          <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
            <mainClass>com.telegram_bot.Main</mainClass>
          </transformer>
        </transformers>
      </configuration>
    </execution>
  </executions>
</plugin>

Thin JAR

For a slimmer artifact, package only project classes and supply dependencies on the classpath at runtime.

Running the Bot

Build the project with mvn package and run the resulting JAR:

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java -jar target/telegram_bot-1.0-SNAPSHOT.jar

Conclusion

Exploring Maven’s packaging options clarified the difference between Fat and Thin JARs and helped me publish a working Telegram bot.