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How to run a Java/Maven application with external libraries in Heroku?

I've been building a Java application, which runs as expected when executing it locally. Now I'm trying the next step, to move it into an external platform. I chose Heroku because of their free plans for a starter, and also because it lets me have a small PostGreSQL database, which I use along with the application.
Due to the way Heroku works, I was forced to integrate Java with Maven, which I know little to none about. But I was still able to work my way there until I was able to compile and deploy the application (source code is in GitHub), albeit with errors.
For once, I'm using a couple external libraries:
jsoup-1.13.1.jar – Jsoup, for easier parsing of HTML files
mail.jar – Java mail, for emailing reports
Whenever the application is deployed in Heroku, there's an Exception in thread "main" java.lang.NoClassDefFoundError: org/jsoup/Jsoup, ultimately triggered by the Jsoup.connect invocation. From what I understand, Maven only add the references to the program but does not include the actual libraries there for runtime, which I think may be the cause of the issue.
I've tried modifying my pom.xml file by adding these dependencies manually:
<dependencies>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>42.2.18</version>
</dependency>
<dependency>
<groupId>com.sun.mail</groupId>
<artifactId>javax.mail</artifactId>
<version>1.6.2</version>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.13.1</version>
</dependency>
</dependencies>
And also these plugins in the build section:
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.0.0</version>
<configuration>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<finalName>checker</finalName>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.4</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
</execution>
</executions>
</plugin>
What am I doing wrong? I would be very grateful for hints to help me get my application running, at least resolving the reason why Jsoup isn't working at all in Heroku. Thanks in advance!

neo4j procedure depending on signed jar (mapdb)

I have created a neo4j user-defined procedure. It also compiles and works in neo4j.
Recently though, I added a dependency to my procedure plugin that prevents neo4j from starting when I try to run the newly built jar. Concretely, I receive following exception at the bottom of the stack trace:
Caused by: java.lang.SecurityException: Invalid signature file digest for Manifest main attributes
The only thing I changed is to add MapDB to my dependencies. So I suspect that it depends on some signed artifact. As it turns out neo4j plugins are "uber-jars" (i.e., shaded jars) which doesn't work very well with signed dependencies.
I figured I could try to exclude MapDB from the shading by changing the scope to provided and additionally adding the mapdb jar to plugins folder of neo4j. So the plugins folder of neo4j now includes both mapdb.jar and myprocedure.jar.
This doesn't seem to work though: neo4j starts, but when calling my procedure I receive a ClassNotFound Exception.
Any ideas on how I can solve this dilemma? I really depend on something like MapDB as my graph is very large and keeping everything in my procedure in-memory regularly leads to memory exceptions.
Many thanks in advance!
The important part of my pom.xml should it help (I started off with the procedure template so it still looks quite similar):
<dependencies>
<!-- other dependencies that don't make a difference ... -->
<dependency>
<groupId>org.mapdb</groupId>
<artifactId>mapdb</artifactId>
<version>3.0.7</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.neo4j</groupId>
<artifactId>neo4j</artifactId>
<version>${neo4j.version}</version>
<scope>provided</scope>
</dependency>
<!-- Test Dependencies -->
<dependency>
<groupId>org.neo4j.test</groupId>
<artifactId>neo4j-harness</artifactId>
<version>${neo4j.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.neo4j.driver</groupId>
<artifactId>neo4j-java-driver</artifactId>
<version>1.4.2</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<!-- Neo4j Procedures require Java 8 -->
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<!-- This generates a jar-file with our procedure code,
plus any dependencies marked as `compile` scope.
This should then be deployed in the `plugins` directory
of each Neo4j instance in your deployment.
After a restart, the procedure is available for calling. -->
<artifactId>maven-shade-plugin</artifactId>
<version>2.4.3</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

So, one solution that worked was to use the maven-assembly-plugin instead of the maven-shade-plugin. The assembly plugin creates a standalone jar with all dependencies without re-packaging all dependencies.
Of course, I had to remove the <scope>provided</scope> for mapdb so it is also included in the assembled jar.
The rest is just replacing the shade plugin with following snippet (thanks to this question here):
<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>
Afterwards I received another exception which I thought was due to a wrong signature:
Caused by: java.lang.VerifyError ...
Turns out this was just because I had another procedure in neo4j that uses the same dependencies as mapdb. Quick fix was to remove that procedure library.
Of course, there are also other solutions, including removing the signature, or re-signing it. However, I explicitly did not want to remove any signatures.

I'm not aware that neo4j is checking any jar signatures by default. I suspect the repackaging of mapdb artifact being the culprit.
To validate that, remove the shade or assembly plugin in and build a jar that solely contains your code. Copy that jar and the mapdb.jar into the plugin folder and observe logs during a restart.

process-resource-bundles maven error calssnotfoundexception org.apache.commons.collections.ExtendedProperties

Trying to build an example from camel via mvn package
apache-camel-2.22.0/examples/camel-example-cdi-xml
Getting an error never seen before, i checked dependency tree for transitive deps and apache-collections is 3.2.1 and not corrupt so can't explain it, obviously i know what it means, just can't figure out why it's happening because everything that should be required is provided:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-remote-resources-plugin:1.5:process (process-resource-bundles) on project camel-example-cdi-xml: Execution process-resource-bundles of goal org.apache.maven.plugins:maven-remote-resources-plugin:1.5:process failed: A required class was missing while executing org.apache.maven.plugins:maven-remote-resources-plugin:1.5:process: org/apache/commons/collections/ExtendedProperties
Not really sure how to trouble shoot it.
I tried building with several different versions of maven. JDK = 1.8

update pom.xml add the following code
<plugin>
<artifactId>maven-remote-resources-plugin</artifactId>
<version>1.6.0</version>
<dependencies>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.2.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-lang/commons-lang -->
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.6</version>
</dependency>
</dependencies>
<executions>
<execution>
<goals>
<goal>bundle</goal>
</goals>
</execution>
</executions>
</plugin>

Aspectj getting compile error when using the Java 8 class Supplier

I'm trying to use some nifty lazy logging tricks in my logging layer but AspectJ is choking on it. I have a facade in front of log4j. Here's the code:
public void debug ( Supplier<String> message )
{
if( isDebugEnabled() )
{
debug( message.get() );
}
}
The error:
[ERROR] The type java.util.function.Supplier cannot be resolved. It is indirectly referenced from required .class files
/home/Build/src/Core/Database/src/com/BasicDao.java:1006
LOGGER.debug( "Retry number: "+retryCount+"DB Lock Conflict, sleeping "+retrySleepTime );
Here's my pom bits:
<plugin>
<!-- This plugin integrates aspectj into our build cycle -->
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
<version>1.7</version>
<configuration>
<complianceLevel>1.8</complianceLevel>
<source>1.8</source>
<target>1.8</target>
</configuration>
<dependencies>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjtools</artifactId>
<version>1.8.5</version>
</dependency>
</dependencies>
<executions>
<execution>
<phase>process-sources</phase>
<goals>
<goal>compile</goal>
<goal>test-compile</goal>
</goals>
</execution>
</executions>
</plugin>
And:
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.8.5</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.8.5</version>
</dependency>
Other interesting facts are that this compiles fine within Eclipse, but I get this error when running mvn package from a Linux command line.
Upon further trial/error we have discovered that if we manually set JAVA_HOME to point to Java 8 then it compiles. It looks like AspectJ requires your JAVA_HOME to point to the right version of Java. In the main pom we are directing maven to use the specific version of Java with:
<executable>${JAVA_1_8_HOME}/bin/javac</executable>
<jvm>${JAVA_1_8_HOME}/jre/bin/java</jvm>
Neither of those seemed to work with the aspectj-maven-plugin configuration.

How to increase aspectj-maven-plugin's memory limit

I'm trying to build project with Maven, but I'm getting this error:
[INFO] --- aspectj-maven-plugin:1.4:compile (default) # core ---
[ERROR] ABORT
[ERROR] AspectJ 1.6.1 ran out of memory during compilation:
Please increase the memory available to ajc by editing the ajc script
found in your AspectJ installation directory. The -Xmx parameter value
should be increased from 64M (default) to 128M or even 256M.
I tried configure aspectj-maven-plugin in pom.xml, but it doesn't take any effect:
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>aspectj-maven-plugin</artifactId>
<version>1.4</version>
<dependencies>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.6.1</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjtools</artifactId>
<version>1.6.1</version>
</dependency>
</dependencies>
<configuration>
<argLine>-Xmx1024m</argLine>
<source>1.6</source>
<target>1.6</target>
<encoding>UTF-8</encoding>
</configuration>
<executions>
<execution>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
My local copy works fine, this error happens only in deployment. How it can be fixed?

export MAVEN_OPTS="-Xmx2048m -XX:MaxPermSize=512m"
into the build script solved the problem. (I tried to use 1024m)

I can't seem to find any memory usage options in the plugin manual. Maybe you should do as it suggests and manually change the ajc script in your local installation directory (although I must admit it seems a poor solution)