Vertx 3 – FatJar alternative

Posted: May 15, 2015 in Java, Microservices
Tags: , , , ,

Vertx3 is nearing its release date and we’re experimenting with the upcoming release to minimize future surprises. One of the major changes is the generation of fatjars. The Vertx2 fatJar plugin doesn’t exist anymore in the Vertx 3 world. Now Vertx 3 uses the maven-shade-plugin to generate the fat JAR. Unfortunately, the shader has its own problems. For example, it is very cumbersome to handle duplicate files especially in transitive dependencies which are something out of your control.

When you’re running into unsolvable errors with the maven-shade-plugin, you can easily switch to the onejar-maven-plugin. Configure your POM as follows:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>2.6</version>
    <configuration>
        <archive>
            <manifestEntries>
                <Main-Class>io.vertx.core.Starter</Main-Class>
                <Main-Verticle>io.vertx.example.HelloWorldVerticle</Main-Verticle>
            </manifestEntries>
        </archive>
    </configuration>
</plugin>
<plugin>
    <groupId>org.dstovall</groupId>
    <artifactId>onejar-maven-plugin</artifactId>
    <version>1.4.5</version>
    <executions>
        <execution>
            <configuration>
                <attachToBuild>true</attachToBuild>
                <filename>service.jar</filename>
            </configuration>
            <goals>
                <goal>one-jar</goal>
            </goals>
        </execution>
    </executions>
</plugin>

This will create a new fat JAR with the project JARs as a complete file on the inside. They are not unpacked, so there are no issues with overwriting files in the META-INF. The downside is that they use an own boot-mechanism.

This again has some problems when for example certain JARs use the SPI mechanism or self-cooked mechanisms to load classes.

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