When I Eclipse project to maven, Why can't I export a .jar without "Fat Jar Export: Could not find class-path for ...target/test-classes - export

Question

I had a working Eclipse project for which I could export a .jar file with no problems.
I then did a 'configure/convert to maven'. Now, when I try to export the .jar file I get the error message:
Fat Jar Export: Could not find class-path entry for 'Users/ward/dropbox/workspaces/newautomation/workspace/automation/target/test-classes'.
Although it does write the .jar file, the .jar file does not work properly.
Any help?
ward

Answer 1

As stated in my question, I had a project running in Eclipse and could successfully 'export a runnable jar' using Eclipse. That allowed me to distribute my project as a self contained '.jar' and run it on other systems with a simple:
java -jar project.jar
I am using Eclipse 4.3.0.
I decided I wanted to covert the project to a 'maven project' and did so using eclipse 'project/configure/convert to maven'.
I then found that my old mechanism for creating a .jar no longer worked.
Casting about the internet I finally found the information I needed. The first bit of information was that I needed to create what was called a 'Fat Jar'. When using maven, one creates a 'Fat Jar' by running maven, NOT using the export function in Eclipse. To create a 'Fat Jar', one needs to click on 'Project/Run As' and select 'maven build'. That will get you to a screen where you specify 'Goals'. Ultimately, for me, the goals were "compile assembly:single".
Doing this for the first time will result in warnings and errors. The most important error is:
Failed to execute goal org.apache.maven.plugins:maven-assembly-plugin:2.2-beta-5:single
This is because the 'pom.xml' file created by the 'convert' process is incomplete. After several frustrating hours, here is what I finally made work. Again, to create the 'Fat Jar', I do:
project/Run As/Maven build
with goals: compile assembly:single
My 'pom.xml' is:
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>example</groupId>
<artifactId>example</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>HelloWorld</name>
<description>Hello World Example</description>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
</properties>
<build>
<sourceDirectory>src</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<release>17</release>
</configuration>
</plugin>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.3.0</version>
<configuration>
<archive>
<manifest>
<mainClass>example.HelloWorld</mainClass>
</manifest>
</archive>
<finalName>helloWorld</finalName>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
</project>
Final notes:
The section concerning 'UTF-8' is not strictly needed, it just gets rid of an annoying warning.
There may be other 'unneeded' lines in the 'pom.xml'.
The 'compile' may be unnecessary but I found that when editing the pom.xml file I often got rid of Eclipse syntax type errors by running 'compile' and so I just do it as a matter of course now.