Develop Reference

Building multiple component zips for a multi-module Maven project

I am trying to find a good example on how you would build multiple zip files for a multi-module project with several runnable components using the maven-assembly-plugin.
My end result would hopefully have a single "dist" component that is capable of building all the necessary zip files.
<?xml version="1.0" encoding="UTF-8"?>
<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>xyz.exampleproject</groupId>
<artifactId>parent</artifactId>
<version>1.0.0-SNAPSHOT</version>
</parent>
<name>Project Distribution</name>
<artifactId>dist</artifactId>
<packaging>pom</packaging>
<dependencies>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>component1-core</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>component2-core</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<id>make-bundles</id>
<goals>
<goal>single</goal>
</goals>
<phase>package</phase>
<configuration>
<descriptors>
<descriptor>assembly.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

I would add one extra module per zip file that you want to create and configure the assembly plugin in there.

Why Executable jar created using maven-assembly-plugin for a multi-module maven project showing classnotfound error

I am trying to create an executable jar for my multi-module maven project. I used the maven-assembly-plugin to generate the jar.
Even though am getting the jar created, am getting the ClassNotFound exception while trying to run the jar file using java -jar command.

Use the shade plugin, much easier than assembly.
Parent pom to hold it all together:
<?xml version="1.0" encoding="UTF-8"?>
<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>fat-jar</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<modules>
<module>library-jar</module>
<module>final-jar</module>
</modules>
</project>
Final build jar pom, with dependency to library:
<?xml version="1.0" encoding="UTF-8"?>
<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>
<artifactId>fat-jar</artifactId>
<groupId>com.greg</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>final-jar</artifactId>
<dependencies>
<dependency>
<groupId>com.greg</groupId>
<artifactId>library-jar</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.2.1</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>com.greg.App</mainClass>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

There is some mistake in you descriptor or how you are using the assembly plugin.
A jar file is like a zip, just open your jar and find your class, if you don't find it then check your pom file or descriptor to understand why.

Trying to build uberjar from multiple maven modules

I am trying to build a single uber-jar from a set a modules that are mostly independent, but it's not working the way I'd thought.
I was initially directed here: https://maven.apache.org/plugins/maven-assembly-plugin/examples/multimodule/module-binary-inclusion-simple.html though now I'm not quite certain that this was what I should have started with...
The parent pom file looks like this:
<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.mycompany</groupId>
<artifactId>BigProject</artifactId>
<version>0.0.1</version>
<packaging>pom</packaging>
<name>BigProject</name>
<modules>
<module>../mod1</module>
<module>../mod2</module>
<!-- ...a bunch more... -->
<module>../distribution</module>
</modules>
<build>
<pluginManagement>
<plugins>
<!-- not even sure why this needs to be specified here, but the documentation seems to think it's important... -->
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.1.0</version>
<configuration>
<descriptors>
<descriptor>src/assembly/assembly.xml</descriptor>
</descriptors>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
The pom for the "distribution" module looks like this:
<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>
<artifactId>distribution</artifactId>
<name>distribution</name>
<packaging>pom</packaging>
<parent>
<groupId>com.mycompany</groupId>
<artifactId>BigProject</artifactId>
<version>0.0.1</version>
</parent>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.1.0</version>
<executions>
<execution>
<id>distro-assembly</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>src/assembly/assembly.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
And finally, the assembly file:
<assembly xmlns="http://maven.apache.org/ASSEMBLY/2.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/ASSEMBLY/2.0.0 http://maven.apache.org/xsd/assembly-2.0.0.xsd">
<id>bin</id>
<formats>
<format>dir</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<moduleSets>
<moduleSet>
<includeSubModules>true</includeSubModules>
<useAllReactorProjects>true</useAllReactorProjects>
<includes>
<include>com.myCompany:mod1</include>
<include>com.myCompany:mod2</include>
<!-- and others... -->
</includes>
<binaries>
<includeDependencies>true</includeDependencies>
<outputDirectory>modules/maven-assembly-plugin</outputDirectory>
<unpack>false</unpack>
</binaries>
</moduleSet>
</moduleSets>
</assembly>
(I realize that at some point I will probably need to change <format>dir</format> to <format>jar</format> but for now, I'd just like to get something working)
When I run mvn clean package from the main parent module's directory, I get warnings like this:
[INFO] Reading assembly descriptor: src/assembly/assembly.xml
[WARNING] The following patterns were never triggered in this artifact inclusion filter:
o 'com.myCompany:mod1'
o 'com.myCompany:mod2'
...
Followed by the error:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-assembly-plugin:3.1.0:single (distro-assembly) on project distribution: Failed to create assembly: Error creating assembly archive bin: archive cannot be empty -> [Help 1]
What I actually want:
One jar file containing all of my modules, and all of their dependencies (that is, the *-with-dependencies.jars), as a single jar file with everything contained inside.
I'm really not sure how to achieve this in a multi-module context.

I think I may have resolved it: the child modules mod1, mod2, ... were missing the parent module dependency. I've added
<parent>
<groupId>com.mycompany</groupId>
<artifactId>BigProject</artifactId>
<version>0.0.1</version>
</parent>
to the relevant child modules and now the build doesn't fail, but populates the target directory under the distribution project.

java.lang.NoClassDefFoundError while finding class in package

I have project (TeamCity plugin), written in Scala, packaged by maven and running on TeamCity(which uses Spring).
There is the dependency com.ullink.slack.simpleslackapi in my project. Now I try to update it (from 0.5.2 to 1.2.0) and become an error at runtime.
Error java.lang.NoClassDefFoundError: Could not initialize class
com.ullink.slack.simpleslackapi.impl.SlackWebSocketSessionImpl
The code that caused this exception is pretty simple:
val session = SlackSessionFactory.createWebSocketSlackSession(config.oauthKey)
My build/pom.xml file looks like
<?xml version="1.0" encoding="UTF-8"?>
<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>
<parent>
<artifactId>***</artifactId>
<groupId>***</groupId>
<version>1.0.0</version>
</parent>
<artifactId>build</artifactId>
<packaging>pom</packaging>
<dependencies>
<dependency>
<groupId>***</groupId>
<artifactId>***-server</artifactId>
<version>1.0.0</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.1.0</version>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<finalName>***</finalName>
<outputDirectory>${project.parent.build.directory}</outputDirectory>
<appendAssemblyId>false</appendAssemblyId>
<descriptors>
<descriptor>plugin-assembly.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
I've tried to append this dependency to this file and tried maven-shade-plugin — it does not help.
Could you advice what else can I try?

How to tell the maven-shade-plugin to preserve signatures?

I am using the maven-shade-plugin to combine two seperate jars into a single combined jar.
One of the jars is signed, while the other is not.
If I use the default configuration of the plugin, it will build a broken jar as the new manifest is missing the digest needed by the signature.
I could "fix" the jar by excluding the signature files, but this will of course result in a completely unsigned jar.
I am looking for a way to create a combined jar with all the signed classes remaining signed and valid. - The jar format allows those kind of jars but I could not find an easy way to tell the shade plugin to do so.
Should I write my own transformer to do a proper merging of manifest files or is there already a suitable option in the shade-plugin I did not find, yet?
Example:
pom.xml (defining two modules "foo" and "bar")
<?xml version="1.0"?>
<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>mygroup</groupId>
<artifactId>myparent</artifactId>
<packaging>pom</packaging>
<version>1.0</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<modules>
<module>foo</module>
<module>bar</module>
</modules>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<addMavenDescriptor>false</addMavenDescriptor>
</archive>
</configuration>
</plugin>
</plugins>
</build>
</project>
foo/pom.xml: (combine signed bar into unsigned foo)
<?xml version="1.0"?>
<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>
<parent>
<groupId>mygroup</groupId>
<artifactId>myparent</artifactId>
<version>1.0</version>
</parent>
<artifactId>foo</artifactId>
<dependencies>
<dependency>
<groupId>mygroup</groupId>
<artifactId>bar</artifactId>
<version>1.0</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.3</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<manifestEntries>
<Main-Class>Foo</Main-Class>
</manifestEntries>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
bar/pom.xml: (create signed bar)
<?xml version="1.0"?>
<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>
<parent>
<groupId>mygroup</groupId>
<artifactId>myparent</artifactId>
<version>1.0</version>
</parent>
<artifactId>bar</artifactId>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jarsigner-plugin</artifactId>
<version>1.3.2</version>
<configuration>
<keystore>${user.home}/keystore-name</keystore>
<alias>alias-name</alias>
<storepass>123456</storepass>
</configuration>
<executions>
<execution>
<id>sign</id>
<goals>
<goal>sign</goal>
</goals>
</execution>
<execution>
<id>verify</id>
<goals>
<goal>verify</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
If both modules contain a single hello-word class, I would expect java -jar foo/target/foo-1.0.jar to work and jarsigner -verify foo/target/foo-1.0.jar to tell about the presence of signed classes.

The maven shade plugin does not play nicely with signed jars. I would recommend you take a look at Capsule that is way better to do this kind of job.