How to configure Maven shade plugin in a multi-module project?

Question

I have been trying to get jar using Maven Shade Plugin, but I still don't get a success.

This is my project structure:

MainModule
  -Module1
    -src
    -pom.xml
  -Module2
    -src
    -pom.xml
  -pom.xml

Module1 (pom.xml):

<parent>
    <artifactId>MainModule</artifactId>
    <groupId>com.plugintest</groupId>
    <version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>Module1</artifactId>

Module2 (pom.xml):

<parent>
    <artifactId>MainModule</artifactId>
    <groupId>com.plugintest</groupId>
    <version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>Module1</artifactId>

MainModule (pom.xml):

<groupId>com.plugintest</groupId>
<artifactId>MainModule</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
    <module>Module1</module>
    <module>Module2</module>
</modules>
<build>
    <plugins>
        <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>2.2</version>
        <executions>
            <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
            </execution>
        </executions>
        </plugin>
    </plugins>
</build>

According this code I get 2 jar-files (Module1-version.jar and Module2-version.jar). But it is not what I want. I wish to get 1 jar file (MainModule-version.jar), which would contain the other (Module1 and Module2).

Why doesn't this Shade Plugin work?

Solution

You MainModule is not supposed to produce a jar file. It can produce only... pom files. It contains configuration shared across all it child modules. This is why the shade plugin is called against each modules.

Instead, create a third module. Let's call it FinalModule. This module is a child of MainModule. Move the whole <build> node from MainModule pom.xml to FinalModule pom.xml.

File structure:

   MainModule
      -FinalModule
        -src
        -pom.xml
      -Module1
        -src
        -pom.xml
      -Module2
        -src
        -pom.xml
      -pom.xml

The FinalModule pom.xml looks like this:

FinalModule (pom.xml)

<parent>
    <groupId>com.plugintest</groupId>
    <artifactId>MainModule</artifactId>
    <version>1.0-SNAPSHOT</version>
</parent>
<artifactId>FinalModule</artifactId>

<dependencies>
    <dependency>
        <groupId>com.plugintest</groupId>
        <artifactId>Module1</artifactId>
        <version>1.0-SNAPSHOT</version>
    </dependency>
    <dependency>
        <groupId>com.plugintest</groupId>
        <artifactId>Module2</artifactId>
        <version>1.0-SNAPSHOT</version>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>2.2</version>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

In the end, you should get something like this:

[INFO] 
[INFO] --- maven-jar-plugin:2.3.2:jar (default-jar) @ FinalModule ---
[INFO] Building jar: D:\workspaces\java\Parent\FinalModule\target\FinalModule-1.0-SNAPSHOT.jar
[INFO] 
[INFO] --- maven-shade-plugin:2.2:shade (default) @ FinalModule ---
[INFO] Including my:Module1:jar:1.0-SNAPSHOT in the shaded jar.
[INFO] Including my:Module2:jar:1.0-SNAPSHOT in the shaded jar.
[INFO] Replacing original artifact with shaded artifact.
[INFO] Replacing D:\workspaces\java\Parent\FinalModule\target\FinalModule-1.0-SNAPSHOT.jar with D:\workspaces\java\Parent\FinalModule\target\FinalModule-1.0-SNAPSHOT-shaded.jar
[INFO] Dependency-reduced POM written at: D:\workspaces\java\Parent\FinalModule\dependency-reduced-pom.xml
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] Parent ............................................ SUCCESS [0.016s]
[INFO] Module1 ........................................... SUCCESS [1.654s]
[INFO] Module2 ........................................... SUCCESS [0.343s]
[INFO] FinalModule ....................................... SUCCESS [0.953s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

Comments

[Andy]

I take back my previous comments...I was confused/frustrated because I thought this approach requires using <parent> pom links. Thankfully, it doesn't; even without them, the module containing the shade config will output the shaded jar when you run mvn install on the aggregation pom.