Maven: Is it possible to create a fat jar containing only dependencies and a jar with only application code?

Question

I used following in my pom.xml to create the fat jar:

<plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <executions>
              <execution>
                <phase>package</phase>
                <goals>
                  <goal>single</goal>
                </goals>
              </execution>
            </executions>
            <configuration>
              <descriptorRefs>
                <descriptorRef>jar-with-dependencies</descriptorRef>
              </descriptorRefs>
            </configuration>
      </plugin>

But this includes the application code as well. I want to make 2 jars, one with only application code and another single jar with only dependencies.

I also tried this:

<plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <version>2.5.1</version>
            <executions>
              <execution>
                <id>copy-dependencies</id>
                <phase>package</phase>
                <goals>
                <goal>copy-dependencies</goal>
                </goals>
                <configuration>
                <outputDirectory>${project.build.directory}/lib/</outputDirectory>
                </configuration>
              </execution>
            </executions>
        </plugin>

but it just puts all the dependency jars in a single folder.

Answer 1

The cleanest way of doing this ls to have a multi module maven project where 3 projects do separate jobs, here is an example.

The parent holds it all together:

<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.greg</groupId>
    <artifactId>two-fat-jars</artifactId>
    <version>1.0</version>
    <packaging>pom</packaging>

    <name>two-fat-jars</name>
    <url>http://maven.apache.org</url>

    <modules>
        <module>common</module>
        <module>application-jar</module>
        <module>dependencies-jar</module>
    </modules>

</project>

The first project builds the code

<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.greg</groupId>
        <artifactId>two-fat-jars</artifactId>
        <version>1.0</version>
    </parent>

    <artifactId>common</artifactId>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
        </dependency>
    </dependencies>

</project>

The second project has a dependency to the common project and builds the application jar, excluding certain dependencies:

<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
<parent>
    <groupId>com.greg</groupId>
    <artifactId>two-fat-jars</artifactId>
    <version>1.0</version>
</parent>

<artifactId>application-jar</artifactId>
<packaging>jar</packaging>

<dependencies>
    <dependency>
        <groupId>com.greg</groupId>
        <artifactId>common</artifactId>
        <version>${project.version}</version>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.1.0</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <artifactSet>
                            <excludes>
                                <exclude>junit:junit</exclude>
                            </excludes>
                            <includes>
                                <include>com.greg:common</include>
                            </includes>
                        </artifactSet>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

The third project builds the dependencies jar by excluding the application code dependencies:

<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<parent>
    <groupId>com.greg</groupId>
    <artifactId>two-fat-jars</artifactId>
    <version>1.0</version>
</parent>

<artifactId>dependencies-jar</artifactId>
<packaging>jar</packaging>

<dependencies>
    <dependency>
        <groupId>com.greg</groupId>
        <artifactId>common</artifactId>
        <version>${project.version}</version>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.1.0</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <artifactSet>
                            <excludes>
                                <exclude>com.greg:common</exclude>
                            </excludes>
                        </artifactSet>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

This is the example code structure:

./pom.xml
./application-jar
./application-jar/pom.xml
./application-jar/dependency-reduced-pom.xml
./dependencies-jar
./dependencies-jar/pom.xml
./common
./common/src
./common/src/main
./common/src/main/java
./common/src/main/java/com
./common/src/main/java/com/greg
./common/src/main/java/com/greg/App.java
./common/src/main/resources
./common/src/main/resources/configs
./common/src/main/resources/configs/config1.xml
./common/src/main/resources/configs/config2.xml
./common/src/main/resources/test2.properties
./common/src/main/resources/test1.properties
./common/src/test
./common/src/test/java
./common/src/test/java/com
./common/src/test/java/com/greg
./common/src/test/java/com/greg/AppTest.java
./common/pom.xml
./common/configs
./common/configs/config1.xml
./common/configs/config2.xml