exec-maven-plugin error, even on working example

Question

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

Answer 1

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

Answer 2

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"