title: No plugin found for prefix 'exec' in the current project and in the plugin groups [org.apache.maven.plugins, org.codehaus.mojo]
body: <p>I am new to Maven, I am trying to build an project using Maven 3.3 but I have encountered an following error using the command mvn clean install exec:java in command prompt.</p>
  
  <pre><code>[WARNING] Could not transfer metadata org.codehaus.mojo/maven-metadata.xml from/to mirrorId (https://oss.sonatype.org/content/repositories): http://http=server.proxyserver.com
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD FAILURE
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time: 1.132 s
  [INFO] Finished at: 2016-09-22T18:59:14+05:30
  [INFO] Final Memory: 8M/113M
  [INFO] ------------------------------------------------------------------------
  [ERROR] No plugin found for prefix 'exec' in the current project and in the plugin groups [org.apache.maven.plugins, org.codehaus.mojo] available from the repositories [local (C:\Users\xxx\.m2\repository), mirrorId (https://oss.sonatype.org/content/repositories)] -&gt; [Help 1]
  </code></pre>
  
  <p>I have changed my proxy settings in my POM.xml and my POM is,</p>
  
  <pre><code>&lt;plugin&gt;
                  &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
                  &lt;artifactId&gt;exec-maven-plugin&lt;/artifactId&gt;
                  &lt;version&gt;1.4.0&lt;/version&gt;
                  &lt;executions&gt;
                      &lt;execution&gt;
                          &lt;goals&gt;
                              &lt;goal&gt;java&lt;/goal&gt;
                          &lt;/goals&gt;
                      &lt;/execution&gt;
                  &lt;/executions&gt;
                  &lt;configuration&gt;
                      &lt;includeProjectDependencies&gt;false&lt;/includeProjectDependencies&gt;
                      &lt;includePluginDependencies&gt;true&lt;/includePluginDependencies&gt;
                      &lt;executableDependency&gt;
                          &lt;groupId&gt;org.kaaproject.kaa.demo.zeppelin&lt;/groupId&gt;
                          &lt;artifactId&gt;simulator&lt;/artifactId&gt;
                      &lt;/executableDependency&gt;
                      &lt;mainClass&gt;org.kaaproject.kaa.demo.zeppelin.Simulator&lt;/mainClass&gt;
                  &lt;/configuration&gt;
                  &lt;dependencies&gt;
                      &lt;dependency&gt;
                          &lt;groupId&gt;org.kaaproject.kaa.demo.zeppelin&lt;/groupId&gt;
                          &lt;artifactId&gt;simulator&lt;/artifactId&gt;
                          &lt;version&gt;1.2.0-SNAPSHOT&lt;/version&gt;
                          &lt;type&gt;jar&lt;/type&gt;
                      &lt;/dependency&gt;
                  &lt;/dependencies&gt;
              &lt;/plugin&gt;
  </code></pre>
  
  <p>and my settings.xml is,</p>
  
  <pre><code>&lt;proxies&gt;
     &lt;proxy&gt;
        &lt;id&gt;optional&lt;/id&gt;
        &lt;active&gt;true&lt;/active&gt;
        &lt;protocol&gt;http&lt;/protocol&gt;
        &lt;host&gt;http://http=xxx.proxyserver.com&lt;/host&gt;
        &lt;port&gt;8080&lt;/port&gt;
        &lt;nonProxyHosts&gt;local.net|some.host.com&lt;/nonProxyHosts&gt;
      &lt;/proxy&gt;
    &lt;/proxies&gt;
  </code></pre>
  
  <p>Thanks inadvance.. Looking forward to hear...Even last posted regarding is not helpful.</p>