Maven, maven-assembly-plugin and scala-library.jar file

Question

I am having a bad time configuring my pom.xml to do what i want.

I would like to package my project as a single executable jar file.

Here is the command i use:

• mvn clean compile assembly:single

My current pom.xml do the work, the resulting jar file in the target folder is indeed executable but if i list the files in it, there is 4202 files (my helo world+4201 files from scala language).

Is it normal ? isn't there a way to build my jar with a scala-library.jar in it ? how ?

Pom.xml :

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.myself</groupId>
<artifactId>cacrawler</artifactId>
<version>1.0-SNAPSHOT</version>
<name>${project.artifactId}</name>
<description>My wonderfull scala app</description>
<inceptionYear>2010</inceptionYear>
<licenses>
    <license>
        <name>My License</name>
        <url>http://....</url>
        <distribution>repo</distribution>
    </license>
</licenses>

<properties>
    <maven.compiler.source>1.5</maven.compiler.source>
    <maven.compiler.target>1.5</maven.compiler.target>
    <encoding>UTF-8</encoding>
    <scala.version>2.8.0</scala.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.scala-lang</groupId>
        <artifactId>scala-library</artifactId>
        <version>${scala.version}</version>
    </dependency>

    <!-- Test -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.8.1</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.scala-tools.testing</groupId>
        <artifactId>specs_${scala.version}</artifactId>
        <version>1.6.5</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.scalatest</groupId>
        <artifactId>scalatest</artifactId>
        <version>1.2</version>
        <scope>test</scope>
    </dependency>
</dependencies>

<build>
    <sourceDirectory>src/main/scala</sourceDirectory>
    <testSourceDirectory>src/test/scala</testSourceDirectory>
    <plugins>
        <plugin>
            <groupId>org.scala-tools</groupId>
            <artifactId>maven-scala-plugin</artifactId>
            <version>2.15.0</version>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>testCompile</goal>
                    </goals>
                    <configuration>
                        <args>
                            <arg>-make:transitive</arg>
                            <arg>-dependencyfile</arg>
                            <arg>${project.build.directory}/.scala_dependencies</arg>
                        </args>
                    </configuration>
                </execution>
            </executions>
        </plugin>
     <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
        </plugin>
    <plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <configuration>
            <archive>
                <manifest>
                    <mainClass>com.myself.App</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>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.6</version>
            <configuration>
                <useFile>false</useFile>
                <disableXmlReport>true</disableXmlReport>
                <!-- If you have classpath issue like NoDefClassError,... -->
                <!-- useManifestOnlyJar>false</useManifestOnlyJar -->
                <includes>
                    <include>**/*Test.*</include>
                    <include>**/*Suite.*</include>
                </includes>
            </configuration>
        </plugin>
    </plugins>
</build>
</project>

Answer 1

Yes it's normal.

If you include scala-library.jar as jar in your jar then you should include a custom code to load into your main(...).

java -jar xxx.jar ignore jar inside jar

• you have to create your own assembly description file with <unpack>false</unpack> on dependencySet (under binaries or root, I don't remember) + change main to load the jar from Resource (your main() should note depends of scala-library)
• you can use alternative to assembly, dedicated to this job (it includes code to launch jar), like (maven plugin for those tools should exists):
  • onejar
  • launch4j

But my recommendation, it's to use Proguard : it will create a single jar like you current code, but it will shrink useless code (lot of part of scala-library). Try it manually (without maven-plugin first) via the gui to find your right configuraion, it can take time (if you use reflection, ...).