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mvn checkstyle plugin: google_checks no reached

maven checkstyle plugin is telling me that it's using sun_checks.xml by default:
INFO] There are 5 errors reported by Checkstyle 8.29 with sun_checks.xml ruleset.
I mean, I've not located any sun_checks.xml into my project in order to tell checkstyle plugin to use this file.
So, I guess, plugin has available this file by default.
According to documentation, plugin has available two check rulesets by default: sun_checks.xml and google_checks.xml.
I've tried to change it:
<reporting>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-checkstyle-plugin</artifactId>
<version>${checkstyle-plugin.version}</version>
<configuration>
<configLocation>google_checks.xml</configLocation>
</configuration>
</plugin>
</plugins>
</reporting>
After performing mvn checkstyle:check goal, it's telling me that it's using sun_checks.xml instead of google_checks.xml:
$ mvn checkstyle:check
[INFO] Scanning for projects...
[INFO]
[INFO] -------------------< net.gencat.clt.arxius:backend >--------------------
[INFO] Building backend 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-checkstyle-plugin:3.1.1:check (default-cli) # backend ---
[INFO] There are 4 errors reported by Checkstyle 8.29 with sun_checks.xml ruleset.
[ERROR] src/main/java/net/gencat/clt/arxius/backend/BackendApplication.java:[1] (javadoc) JavadocPackage: Missing package-info.java file.
[ERROR] src/main/java/net/gencat/clt/arxius/backend/BackendApplication.java:[6,1] (design) HideUtilityClassConstructor: Utility classes should not have a public or default constructor.
[ERROR] src/main/java/net/gencat/clt/arxius/backend/BackendApplication.java:[9,1] (whitespace) FileTabCharacter: File contains tab characters (this is the first instance).
[ERROR] src/main/java/net/gencat/clt/arxius/backend/BackendApplication.java:[9,9] (javadoc) MissingJavadocMethod: Missing a Javadoc comment.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.265 s
[INFO] Finished at: 2020-10-21T10:45:52+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:3.1.1:check (default-cli) on project backend: You have 4 Checkstyle violations. -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
Any ideas?

You are using the google_checks.xml under <reporting> tag. You can keep it like this but repoting tag as maven.apache.org says: A plugin is actually not a report plugin in itself. But one (or several) of its goals or Mojos may be specialized to be invoked by maven-site-plugin, typically during the site build life cycle.
if you want to use mvn checkstyle:check goal you need to also have:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-checkstyle-plugin</artifactId>
<version>2.17</version>
<executions>
<execution>
<id>checkstyle</id>
<phase>validate</phase>
<goals>
<goal>check</goal>
</goals>
</execution>
</executions>
<configuration>
<configLocation>google_checks.xml</configLocation>
</configuration>
</plugin>
</plugins>
</build>

How to run test from different folder?

I have project
my-tests
src
test
java
my
demo
srv
src
main
java
my
demo
I want to run mvn clean install on srv and then to run the tests from my-tests
I tried to add plugin to the pom.xml of srv
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.12</version>
<executions>
<execution>
<id>add-test-source</id>
<goals>
<goal>add-test-source</goal>
</goals>
<configuration>
<sources>
<source>../my-tests</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
I got an error of compile
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.592 s
[INFO] Finished at: 2020-04-27T16:35:14+03:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:testCompile (default-testCompile) on project sapinttest-srv: Compilation failure: Compilation failure:
[ERROR] /C:/Users/Downloads/app/integration-tests/src/test/java/my/company/HelloWorldServletTest.java:[3,22] package io.restassured does not exist
[ERROR] /C:/Users/Downloads/app/integration-tests/src/test/java/my/company/HelloWorldServletTest.java:[4,47] package org.jboss.arquillian.container.test.api does not exist
[ERROR] /C:/Users/Downloads/app/integration-tests/src/test/java/my/demo/HelloWorldServletTest.java:[5,34] package org.jboss.arquillian.junit does not exist
[ERROR] /C:/Users/Downloads/app/integration-tests/src/test/java/my/demo/HelloWorldServletTest.java:[6,37] package org.jboss.arquillian.test.api does not exist
[ERROR] /C:/Users/Downloads/app/integration-tests/src/test/java/my/demo/HelloWorldServletTest.java:[7,37] package org.jboss.shrinkwrap.api.spec does not exist
[ERROR] /C:/Users//Downloads/app/integration-tests/src/test/java/my/demo/HelloWorldServletTest.java:[8,17] package org.junit does not exist
when I tried to run test from the my-tests folder the compile was ok but the tests didn't run
mvn clean install -DskipTests=false
Could you advise me please ?

Fixing compilation errors
The error message states that some third library packages could not be found.
Being my-tests a Maven module, you should add to its pom.xml the dependencies that contains these packages.
pom.xml
<project>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
<scope>test</scope>
</dependency>
<!-- TODO: Add other dependencies here. -->
</dependencies>
...
</project>
To find which dependency contains the package, you could search on Maven Central using the following criteria:
fc:package-name
e.g.:
fc:org.jboss.arquillian.junit
Direct link: https://search.maven.org/search?q=fc:org.jboss.arquillian.junit
Changing the test folder
Being your goal simply running tests on a folder different than src/test/java, you should change the testSourceDirectory property.
pom.xml
<project>
<build>
<testSourceDirectory>${project.basedir}/src/custom-test-folder/java</testSourceDirectory>
</build>
...
</project>

maven deploy-file missing/invalid file and/or url

When I run my command, I get the following. Note that if I were to run the same thing from the command line ( with -D options ), it would work. So what I am doing wrong? -X and -e show me nothing of any value. I am currently researching if maybe my variables are not being picked up, but the url value is clearly defined, so while that might explain the missing/invalid file error, it would not explain the missing/invalid url error.
mvn deploy:deploy-file
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building jooq-model 1.0
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-deploy-plugin:2.8.2:deploy-file (default-cli) # jooq-model ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.280 s
[INFO] Finished at: 2018-10-23T20:24:49-04:00
[INFO] Final Memory: 6M/92M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-deploy-plugin:2.8.2:deploy-file (default-cli) on project jooq-model: The parameters 'file', 'url' for goal org.apache.maven.plugins:maven-deploy-plugin:2.8.2:deploy-file are missing or invalid -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginParameterException
I am using the following configuration for the maven-deploy-plugin ( tell me if you need more ):
<build>
....
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>buildnumber-maven-plugin</artifactId>
<version>1.4</version>
<executions>
<execution>
<id>buildnumber</id>
<phase>validate</phase>
<goals>
<goal>create</goal>
</goals>
</execution>
</executions>
<configuration>
<format>{0,number}</format>
<items>
<item>buildNumber</item>
</items>
<doCheck>false</doCheck>
<doUpdate>false</doUpdate>
<revisionOnScmFailure>unknownbuild</revisionOnScmFailure>
</configuration>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
<executions>
<execution>
<id>deploy-file</id>
<phase>deploy</phase>
<goals>
<goal>deploy-file</goal>
</goals>
<configuration>
<file>${project.build.directory}/${project.build.finalName}.jar</file>
<url>file://home/tonyb/.m2/repository</url>
<sources>${project.build.directory}/${project.build.finalName}-sources.jar</sources>
<pomFile>pom.xml</pomFile>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
<finalName>${project.artifactId}-${project.version}.${buildNumber}</finalName>
</build>

Regarding to The deploy:deploy-file Mojo, It told us as
The deploy:deploy-file mojo is used primarily for deploying artifacts
to which were not built by Maven.
Especially,
If the following required information is not specified in some way,
the goal will fail:
the artifact file to deploy
the group, artifact, version and packaging
of the file to deploy. These can be taken from the specified pomFile,
and overriden or specified using the command line. When the pomFile
contains a parent section, the parent's groupId can be considered if
the groupId is not specified further for the current project or on the
command line.
the repository information: the url to deploy to and the
repositoryId mapping to a server section in the settings.xml file. If
you don't specify a repositoryId, Maven will try to extract
authentication information using the id 'remote-repository'.
This means we have the built artifact e.g. our-artifact-1.0.jar and would like to deploy it to our repository. When execute the deploy:deploy-file, we have to pass those required parameters via the -D as the following example.
mvn deploy:deploy-file -Durl=file://C:\m2-repo \
-DrepositoryId=some.id \
-Dfile=our-artifact-1.0.jar \
Then if we would like to deploy our building artifact during the Maven Lifecycle, please use mvn deploy instead.

Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile

Given the below pom.xml:
<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.myApp</groupId>
<artifactId>malloc</artifactId>
<version>0.0.1</version>
<packaging>war</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
</properties>
<repositories>
<repository>
<id>project</id>
<url>file:///${basedir}/lib</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>com.myApp</groupId>
<artifactId>myApp.core</artifactId>
<version>1.0.0</version>
</dependency>
... //other dependencies
</dependencies>
<build>
<sourceDirectory>src</sourceDirectory>
<resources>
<resource>
<directory>src</directory>
<excludes>
<exclude>**/*.java</exclude>
</excludes>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.4</version>
<configuration>
<archive>
<manifest>
<addClasspath>true</addClasspath>
</manifest>
<addMavenDescriptor>false</addMavenDescriptor>
</archive>
<webResources>
<webResource>
<directory>${project.build.directory}/WebContent/WEB-INF</directory>
<includes>
<include>web.xml</include>
</includes>
<targetPath>WEB-INF</targetPath>
<filtering>true</filtering>
</webResource>
</webResources>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.10</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/WebContent/WEB-INF/lib</outputDirectory>
<includeScope>runtime</includeScope>
<overWriteReleases>false</overWriteReleases>
<overWriteSnapshots>false</overWriteSnapshots>
<overWriteIfNewer>true</overWriteIfNewer>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
And the following project structure:
I expect the maven-dependency-plugin would copy all the dependencies to the WebContent/WEB-INF/lib but when I run
mvn clean install
The following error is generated:
[INFO] Scanning for projects...
[INFO]
[INFO] Using the builder org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder with a thread count of 1
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building api-malloc 0.0.1
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for com.oracle:ojdbc6:jar:10.2.0.4.0 is missing, no dependency information available
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) # api-malloc ---
[INFO] Deleting C:\Development\malloc\target
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) # api-malloc ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) # api-malloc ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 8 source files to C:\Development\malloc\target\classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[3,34] package com.myApp.api.core.dto does not exist
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[5,39] cannot find symbol
symbol: class IDTO
[INFO] 26 errors
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.209 s
[INFO] Finished at: 2015-11-26T15:33:40-05:00
[INFO] Final Memory: 21M/227M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project malloc: Compilation failure: Compilation failure:
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[3,34] package com.myApp.api.core.dto does not exist
[ERROR] /C:/Development/malloc/src/com/myApp/api/malloc/dto/RegionTypeDTO.java:[5,39] cannot find symbol
[ERROR] symbol: class IDTO
[ERROR] location: class com.myApp.api.malloc.controllers.TestController
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
I noticed the WEB-INF/lib folder is always empty, maven dependencies are not copied over.
I am suspecting the copy-dependencies plugin didn't get run before the compile stage but I can't really figure out - anything that I missed?

The copy-dependencies goal indeed will never be executed if the compilation fails because its binding is to the package phase, which comes after the compile phase (to which by default is linked the Maven Compiler Plugin).
If you want it to run before the compile phase, you need to change the phase value of the execution of the copy-dependencies goal. Changing to process-resources should be fine and should also make sense.
<phase>package</phase>
For a full description of phases, you can check official documentation, here.
You should also fix the compilation errors the build output is pointing at. I see the sourceDirectory element is overriding what Maven uses by default for Java source code (src\main\java), hence I suppose your code is directly under the src folder.
Updated: the package X does not exist error occurs when the code is referring to a package not resolved by the Java compiler, hence it is not able to see that package in the classpath, which means in the declared dependencies: does myApp.core contain that package and class? If yes, then the repositories element (the lib folder) is probably not properly providing the myApp dependency.
You can try to install the dependency locally in your .m2 maven cache using the Maven Install Plugin as specified here.
You could execute from the command line as following:
mvn org.apache.maven.plugins:maven-install-plugin:2.5.2:install-file
-Dfile=lib\myApp.core-1.0.0.jar \
-DgroupId=com.myApp \
-DartifactId=myApp.core \
-Dversion=1.0.0 \
-Dpackaging=jar \
Side note: Maven prefers lower case groupid and artifactid tokens. Moreover, instead of using Camel Case (i.e. myApp), Maven convention is also use a dash for separating tokens (i.e. myapp-core).

exec-maven-plugin error, even on working example

EDIT5 Updated /
I'm using Maven 3.3.3.
I just create new project and added compile and exec plugin, as examples on web.
I tried to execute, but I got error
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project QNAProject: An exception occured while executing the Java class. com.jadex.qna.QNAProject.App -> [Help 1]<br>
[ERROR] <br>
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.<br>
[ERROR] Re-run Maven using the -X switch to enable full debug logging.<br>
[ERROR] <br>
[ERROR] For more information about the errors and possible solutions, please read the following articles:<br>
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException<br>
I tried exec-maven-plugin version 1.2.1 and 1.4.0, but got same error. Here is my pom.xml
<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.jadex.qna</groupId>
<artifactId>QNAProject</artifactId>
<version>0.1</version>
<packaging>jar</packaging>
<name>QNAProject</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.2.1</version>
<executions>
<execution>
<goals>
<goal>java</goal>
</goals>
</execution>
</executions>
<configuration>
<executable>maven</executable>
<mainClass>com.jadex.qna.QNAProject.App</mainClass>
</configuration>
</plugin>
</plugins>
</build>
</project>
I even tried a working example project from several sites,
such as
http://examples.javacodegeeks.com/enterprise-java/maven/create-java-project-with-maven-example/
http://www.mkyong.com/maven/how-to-create-a-java-project-with-maven/
but I got same error.
I unzipped maven at C:\apache-maven-3.3.3 and created environment variable MAVEN_HOME as same path.
What is the problem?
====================================
EDIT: Here is the result
Well.. I set MAVEN_HOME, not M2_HOME because tutorial what I found said to set it only...
Of course, echo %MAVEN_HOME% shows
C:\apache-maven-3.3.3
is it wrong?
I added %MAVEN_HOME%\bin to PATH variable, but it did not work too.
And, I'm using eclipse
=====================================
EDIT2: Here is full log. I used goal 'clean exec:java -e -X'
It was too long, so I uploaded to my blog here.
And note that I changed repository folder from C:\Users.....m2 to new local repository folder C:\apache-maven-localrepository
https://arincblossom.wordpress.com/2015/06/15/error-logs/
=======================================
EDIT3: I changed maven-compiler-plugin setting like this
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<verbose>true</verbose>
<fork>true</fork>
<executable>${env.JAVA_HOME}/bin/javac</executable>
<compilerVersion>1.5</compilerVersion>
<!-- <source>1.8</source>
<target>1.8</target> -->
</configuration>
</plugin>
It prevented me from having error from mvn -e compile exec:java but I can't run with mvn exec:java -Dexec.mainClass="com.jadex.qna.QNAProject.App"
=================================
EDIT4: OK, I'll try from the bottom, and post again. Thanks for your sincere helps.
======================================
EDIT5
I reset all the sequences... re-installed eclipse, maven.. and re-created projects... but nothing worked...
I changed eclipse settings to fix JDK path to installed jdk path, not JRE path. then I found that 'mvn -e clean compile exec:java' is working, but I want to just 'mvn clean exec:java' work. It does not work at all.
You can check full source here
https://github.com/arincblossom/MavenTestProject
This is current console message for 'mvn -e clean exec:java'
[WARNING]
[WARNING] Some problems were encountered while building the effective settings
[WARNING] expected START_TAG or END_TAG not TEXT (position: TEXT seen ...ore artifacts.\n |\n | Default: ${user.home}/.m2/repository\n <l... #53:5) # C:\apache-maven-3.3.3\conf\settings.xml, line 53, column 5
[WARNING] expected START_TAG or END_TAG not TEXT (position: TEXT seen ...ore artifacts.\n |\n | Default: ${user.home}/.m2/repository\n <l... #53:5) # C:\apache-maven-3.3.3\conf\settings.xml, line 53, column 5
[WARNING]
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building MavenTestProject 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) # MavenTestProject ---
[INFO] Deleting C:\Users\bonavision_laptop\Desktop\Project\JadeX\MavenTestProject\MavenTestProject\target
[INFO]
[INFO] --- exec-maven-plugin:1.4.0:java (default-cli) # MavenTestProject ---
[WARNING]
java.lang.ClassNotFoundException: com.jadex.qna.MavenTestProject.App
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:281)
at java.lang.Thread.run(Thread.java:745)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.900 s
[INFO] Finished at: 2015-06-15T17:42:19+09:00
[INFO] Final Memory: 8M/153M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.4.0:java (default-cli) on project MavenTestProject: An exception occured while executing the Java class. com.jadex.qna.MavenTestProject.App -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

This issue happens, when it is not compatible with eclipse too.
Try this
mvn clean install eclipse:eclipse
Vote up, if it works to help fellow members

The error log which you posted says the following:
java.lang.ClassNotFoundException com.jadex.qna.QNAProject.App
So it clear what the root source of the error is. You are trying to execute the main() method of a class whose class file Maven cannot find. As this SO article discusses, you can try explicitly compiling first, then executing after the class file has been generated:
mvn -e compile exec:java
mvn exec:java -Dexec.mainClass="com.jadex.qna.QNAProject.App"

I ran into this same problem, it was caused by a port conflict.
my tomcat server tried to start on port 8080 but i already had a binding for it.
netstat -anto will show you port bindings 0.0.0.0:8080 or similar and it's PID this will help you determin what process is already running the port bidning, either change it in your timcat server or whatever process is using the bidning. Could be caused by an IIS, SKype or similar.