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Could not find or load main class error when adding maven dependency

I got a Maven project which is exported into a JAR and works fine.
As soon as I add Maven dependency (not using any class etc, just imported)
<dependency>
<groupId>technology.tabula</groupId>
<artifactId>tabula</artifactId>
<version>1.0.5</version>
</dependency>
the exported JAR throws the following error:
Error: Could not find or load main class main.MyMain
Any tips how to solve this problem?
I have to use this Lib, but the error already occurs when it's only imported, not used.
pom.xml
<?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>my.group</groupId>
<artifactId>my-art</artifactId>
<version>1.0</version>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>8</source>
<target>8</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>4.0.0</version>
</dependency>
<dependency>
<groupId>com.dropbox.core</groupId>
<artifactId>dropbox-core-sdk</artifactId>
<version>3.1.5</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.10</version>
</dependency>
<dependency>
<groupId>org.jsoup</groupId>
<artifactId>jsoup</artifactId>
<version>1.13.1</version>
</dependency>
<!--<dependency>-->
<!--<groupId>technology.tabula</groupId>-->
<!--<artifactId>tabula</artifactId>-->
<!--<version>1.0.5</version>-->
<!--</dependency>-->
</dependencies>
</project>

The command I use from command line is "java -jar myapp.jar"
You need to specify the classpath for your app if you run it as a jar from the command line. See this post.

Failed to execute goal com.google.cloud.tools:appengine-maven-plugin:2.3.0:run (default-cli) on project backend

I am trying to follow this tutorial https://cloud.google.com/solutions/mobile/mobile-firebase-app-engine-flexible and I keep getting this error. Especially when I run this command:
mvn clean package appengine:run
I have also tried running it in Java 8 with this command:
mvn clean package appengine:run -Djava8=true
I have also tried downgrading to Java 8, still no success.
[ERROR] Failed to execute goal com.google.cloud.tools:appengine-maven-plugin:2.3.0:run (default-cli) on project backend: Failed to run devappserver: com.google.cloud.tools.appengine.operations.cloudsdk.process.ProcessHandlerException: com.google.cloud.tools.appengine.AppEngineException: Non zero exit: 1 -> [Help 1]
My pom.xml file is shown below
<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>com.google.cloud.solutions.flexenv</groupId>
<artifactId>backend</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>App Engine Backend module for Firebase</name>
<url>https://cloud.google.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.showDeprecation>true</maven.compiler.showDeprecation>
<archiveClasses>true</archiveClasses>
<failOnMissingWebXml>false</failOnMissingWebXml>
</properties>
<prerequisites>
<maven>3.5</maven>
</prerequisites>
<!--
The parent pom defines common style checks and testing strategies for our samples.
Removing or replacing it should not affect the execution of the samples in anyway.
-->
<parent>
<groupId>com.google.cloud.samples</groupId>
<artifactId>shared-configuration</artifactId>
<version>1.0.18</version>
</parent>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.google.cloud</groupId>
<artifactId>libraries-bom</artifactId>
<version>10.0.0</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<!-- Compile/runtime dependencies -->
<dependency>
<groupId>com.google.cloud</groupId>
<artifactId>google-cloud-logging</artifactId>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>jstl</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.7.4</version>
</dependency>
<dependency>
<groupId>com.google.firebase</groupId>
<artifactId>firebase-server-sdk</artifactId>
<version>[3.0.0,)</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<finalName>backend</finalName>
<outputDirectory>target/${project.artifactId}-${project.version}/WEB-INF/classes</outputDirectory>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<version>3.8.1</version>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>3.1.0</version>
<configuration>
<archiveClasses>true</archiveClasses>
<webResources>
<!-- in order to interpolate version from pom into appengine-web.xml -->
<resource>
<directory>${basedir}/src/main/webapp/WEB-INF</directory>
<filtering>true</filtering>
<targetPath>WEB-INF</targetPath>
</resource>
</webResources>
</configuration>
</plugin>
<plugin>
<groupId>com.google.cloud.tools</groupId>
<artifactId>appengine-maven-plugin</artifactId>
<version>2.3.0</version>
<configuration>
<projectId>GCLOUD_CONFIG</projectId>
<version>GCLOUD_CONFIG</version>
<promote>true</promote>
</configuration>
</plugin>
</plugins>
</build>
</project>
Can someone please explain why this isn't working

I'm not an expert with Java or Maven and also don't know what is happening but runnning the commands as follows worked for me:
sudo mvn clean package appengine:run
Also you can try:
sudo mvn clean package appengine:deploy
In case it shows an error regarding that mvn is not found, just type the path where mvn is.

maven pom.xml file wont recognize jersey framework

I am trying to import jersey using maven central but, intellij wont read my pom.xml dependency for jersey. The version # shows in red with the following error:
here is the pom.xml textually:
<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>com.example.emanuel</groupId>
<artifactId>jerseyexample</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>jerseyexample Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.core</groupId>
<artifactId>jersey-client</artifactId>
<version>2.19</version>
</dependency>
</dependencies>
<build>
<finalName>jerseyexample</finalName>
<plugins>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
<configuration>
<server>TomcatServer</server>
<path>/newjersey</path>
</configuration>
</plugin>
</plugins>
</build>
</project>
i copied the dependency straight from here

the issue was with my settings.xml file that maven uses to build the project. I had a mirror defined in there that used a proxy and it was blocking the download.

Dagger 2 no classes generated

I want to try something new and use Dagger 2 as my DI framework. So I have the following pom and the "hello world" coffee maker classes (http://google.github.io/dagger/) in my projekt.
But when I do a mvn clean install no classes get generated. As far as I unterstood there should be a "Dagger_CoffeeShop" class generated. Hmmm ... what am I missing?
<modelVersion>4.0.0</modelVersion>
<groupId>kic</groupId>
<artifactId>xfoo</artifactId>
<version>0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>com.google.dagger</groupId>
<artifactId>dagger</artifactId>
<version>2.0-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<dependencies>
<dependency>
<groupId>com.google.dagger</groupId>
<artifactId>dagger-compiler</artifactId>
<version>2.0-SNAPSHOT</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>

For those using Gradle: Make sure you are referencing the Dagger dependencies as following:
compile 'com.google.dagger:dagger:2.0.2'
apt 'com.google.dagger:dagger-compiler:2.0.2'
And in the case if you are running into apt not supported, add
1) Into module app\build.gradle:
apply plugin: 'com.neenbedankt.android-apt'
2) Into project \build.gradle:
buildscript {
dependencies {
classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
}
}

I had the same problem, only with the release version 2.0.
In my case the following two steps solved this problem:
Adding target/generated-sources/annotations to my build path
Adding <forceJavacCompilerUse>true</forceJavacCompilerUse> to the maven compiler plugin
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<dependencies>
<dependency>
<groupId>com.google.dagger</groupId>
<artifactId>dagger-compiler</artifactId>
<version>2.0</version>
</dependency>
</dependencies>
<configuration>
<source>1.8</source>
<target>1.8</target>
<!-- workaround for https://issues.apache.org/jira/browse/MCOMPILER-202 -->
<forceJavacCompilerUse>true</forceJavacCompilerUse>
</configuration>
</plugin>
See also:
https://github.com/google/dagger/pull/103
https://issues.apache.org/jira/browse/MCOMPILER-202

This isn't the best answer. When I used the downloaded JAR files (commented out in the POM file below) mine also wasn't generating the Dagger_ files. Once I added the repository to the POM, everything was working fine.
<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.hello</groupId>
<artifactId>hellodagger</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hellodagger</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<repositories>
<repository>
<id>sonatype</id>
<name>sonatype-repo</name>
<url>https://oss.sonatype.org/content/repositories/snapshots/</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.google.dagger</groupId>
<artifactId>dagger</artifactId>
<version>2.0-SNAPSHOT</version>
<!--<scope>system</scope>-->
<!--<systemPath>${project.basedir}/dagger-2.0-20141216.223138-12.jar</systemPath>-->
</dependency>
<dependency>
<groupId>com.google.dagger</groupId>
<artifactId>dagger-compiler</artifactId>
<version>2.0-SNAPSHOT</version>
<optional>true</optional>
<!--<scope>system</scope>-->
<!--<systemPath>${project.basedir}/dagger-compiler-2.0-20141216.223201-12-jar-with-dependencies.jar</systemPath>-->
</dependency>
</dependencies>
</project>

Maven appears to be ignoring source and target in webapp

I'm getting "Generated servlet error:|try-with-resources is not supported in -source 1.5". 1.5 is maven's default according to another question on the topic, but I thought I had fixed that in my pom.xml -
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.sspo</groupId>
<artifactId>sspo-parent</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>website</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<name>website</name>
<properties>
<jetty.version>9.0.5.v20130815</jetty.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
<plugin>
<groupId>org.eclipse.jetty</groupId>
<artifactId>jetty-maven-plugin</artifactId>
<version>${jetty.version}</version>
<dependencies>
<dependency>
<groupId>commons-dbcp</groupId>
<artifactId>commons-dbcp</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>commons-pool</groupId>
<artifactId>commons-pool</artifactId>
<version>1.6</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.26</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>com.sspso</groupId>
<artifactId>com.sspo.package1</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>com.sspo</groupId>
<artifactId>com.sspo.package2</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.0.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
</project>
Other packages in the project work fine with 1.7, as seen in the parent pom -
<?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.sspo</groupId>
<artifactId>sspo-parent</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<name>sspo-parent</name>
<modules>
<module>try-with-resources-works-here</module>
<module>and-here</module>
<module>even-in-this-one</module>
<module>website</module>
</modules>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>14.0.1</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.2</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.14</version>
</dependency>
</dependencies>
</project>
Ultimately, I think the question is probably "what have I done wrong that maven is ignoring the source and target specifications?" There are similar questions out there, but the ones I've seen are either not solved or suggest things that exist in my pom.
Any help would be appreciated.

Jetty is using 1.5 source and target args by default for JSP compilation. See Jetty embedded and JSP compilation to 1.7? for pointers and info on switching Jetty to use 1.7