Maven project not building
<p>I'm trying to get Maven up and going so I can follow along and study the MongoDb for Java Developers Free course from MongoDb University online.</p>

<p>I'm brand new to Maven and am having problems getting it up and going. I'm getting error message:</p>

<blockquote>
  <p>Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java (default-cli) on project M101J: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java are missing or invalid -> [Help 1]</p>
</blockquote>

<p>When I try to run <code>mvn exec:java</code>, I cannot figure out for the life of me what the deal is here. As I said, I am completely new to using (or trying to use) maven.</p>

<p>Here is the <code>pom.xml</code></p>

<pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;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"&gt;
    &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;

    &lt;groupId&gt;com.mongodb&lt;/groupId&gt;
    &lt;artifactId&gt;M101J&lt;/artifactId&gt;
    &lt;version&gt;1.0-SNAPSHOT&lt;/version&gt;
    &lt;packaging&gt;jar&lt;/packaging&gt;

    &lt;name&gt;M101J&lt;/name&gt;
    &lt;url&gt;http://maven.apache.org&lt;/url&gt;

    &lt;properties&gt;
        &lt;project&gt;build.sourceEncoding&gt;UTF-8&lt;/project&gt;
    &lt;/properties&gt;

    &lt;dependencies&gt;
        &lt;dependency&gt;
            &lt;groupId&gt;junit&lt;/groupId&gt;
            &lt;artifactId&gt;junit&lt;/artifactId&gt;
            &lt;version&gt;3.8.1&lt;/version&gt;
        &lt;/dependency&gt;
    &lt;/dependencies&gt;

&lt;/project&gt;
</code></pre>

<p>I feel as out of place as a scorpion in a nursery right now and could greatly use any help and advice to get me going. Many thanks to all.</p>