title: Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java (default-cli) on project nextrtc-signaling-serverrror
body: <p>I tested nextrtc-signaling-server which is opensource for Java.
  But I encountered building Maven problem. I hope that this is solved.</p>
  
  <p><strong>My console log.</strong></p>
  
  <pre><code> [INFO] Building jar: D:\signallinServer\nextrtc-signaling-server\target\nextrtc-signaling-server-0.0.4-SNAPSHOT-javadoc.jar
   [INFO] 
   [INFO] --- exec-maven-plugin:1.5.0:java (default-cli) @ nextrtc-signaling-server ---
   [INFO] ------------------------------------------------------------------------
   [INFO] BUILD FAILURE
   [INFO] ------------------------------------------------------------------------
   [INFO] Total time: 12.430 s
   [INFO] Finished at: 2016-08-29T11:12:34+09:00
   [INFO] Final Memory: 26M/223M
   [INFO] ------------------------------------------------------------------------
   [ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java (default-cli) on project nextrtc-signaling-server: The parameters 'mainClass' for goal org.codehaus.mojo:exec-maven-plugin:1.5.0:java are missing or invalid -&gt; [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
  </code></pre>
  
  <p><strong>POM.xml</strong></p>
  
  <p>http://maven.apache.org/xsd/maven-4.0.0.xsd">
      4.0.0</p>
  
  <pre><code>&lt;groupId&gt;org.nextrtc.signalingserver&lt;/groupId&gt;
  &lt;artifactId&gt;nextrtc-signaling-server&lt;/artifactId&gt;
  &lt;version&gt;0.0.4-SNAPSHOT&lt;/version&gt;
  &lt;packaging&gt;jar&lt;/packaging&gt;
  
  &lt;name&gt;nextrtc-signaling-server&lt;/name&gt;
  &lt;url&gt;http://nextrtc.org&lt;/url&gt;
  &lt;description&gt;Library providing signaling protocol for WebRTC&lt;/description&gt;
  
  &lt;licenses&gt;
      &lt;license&gt;
          &lt;name&gt;MIT License&lt;/name&gt;
          &lt;url&gt;http://www.opensource.org/licenses/mit-license.php&lt;/url&gt;
      &lt;/license&gt;
  &lt;/licenses&gt;
  
  &lt;developers&gt;
      &lt;developer&gt;
          &lt;name&gt;Marcin Ślósarz&lt;/name&gt;
          &lt;email&gt;m.slosarz@ahej.pl&lt;/email&gt;
          &lt;organization&gt;NextRTC&lt;/organization&gt;
          &lt;organizationUrl&gt;http://nextrtc.org&lt;/organizationUrl&gt;
      &lt;/developer&gt;
  &lt;/developers&gt;
  
  &lt;issueManagement&gt;
      &lt;url&gt;https://github.com/mslosarz/nextrtc-signaling-server/issues&lt;/url&gt;
      &lt;system&gt;GitHub Issues&lt;/system&gt;
  &lt;/issueManagement&gt;
  
  &lt;scm&gt;
      &lt;connection&gt;scm:git:https://github.com/mslosarz/nextrtc-signaling-server.git&lt;/connection&gt;
      &lt;developerConnection&gt;scm:git:git@github.com:mslosarz/nextrtc-signaling-server.git&lt;/developerConnection&gt;
      &lt;url&gt;https://github.com/mslosarz/nextrtc-signaling-server&lt;/url&gt;
  &lt;/scm&gt;
  
  &lt;properties&gt;
      &lt;project.build.sourceEncoding&gt;UTF-8&lt;/project.build.sourceEncoding&gt;
      &lt;maven.compiler.source&gt;1.8&lt;/maven.compiler.source&gt;
      &lt;maven.compiler.target&gt;1.8&lt;/maven.compiler.target&gt;
      &lt;spring-version&gt;4.2.4.RELEASE&lt;/spring-version&gt;
  &lt;/properties&gt;
  
  &lt;distributionManagement&gt;
      &lt;snapshotRepository&gt;
          &lt;id&gt;ossrh&lt;/id&gt;
          &lt;url&gt;https://oss.sonatype.org/content/repositories/snapshots&lt;/url&gt;
      &lt;/snapshotRepository&gt;
      &lt;repository&gt;
          &lt;id&gt;ossrh&lt;/id&gt;
          &lt;url&gt;https://oss.sonatype.org/service/local/staging/deploy/maven2/&lt;/url&gt;
      &lt;/repository&gt;
  &lt;/distributionManagement&gt;
  
  &lt;build&gt;
      &lt;plugins&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-compiler-plugin&lt;/artifactId&gt;
              &lt;version&gt;3.1&lt;/version&gt;
          &lt;/plugin&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-source-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.2.1&lt;/version&gt;
              &lt;executions&gt;
                  &lt;execution&gt;
                      &lt;id&gt;attach-sources&lt;/id&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;jar&lt;/goal&gt;
                      &lt;/goals&gt;
                  &lt;/execution&gt;
              &lt;/executions&gt;
          &lt;/plugin&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-gpg-plugin&lt;/artifactId&gt;
              &lt;version&gt;1.5&lt;/version&gt;
              &lt;executions&gt;
                  &lt;execution&gt;
                      &lt;id&gt;sign-artifacts&lt;/id&gt;
                      &lt;phase&gt;verify&lt;/phase&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;sign&lt;/goal&gt;
                      &lt;/goals&gt;
                  &lt;/execution&gt;
              &lt;/executions&gt;
          &lt;/plugin&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
              &lt;artifactId&gt;maven-javadoc-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.9.1&lt;/version&gt;
              &lt;executions&gt;
                  &lt;execution&gt;
                      &lt;id&gt;attach-javadocs&lt;/id&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;jar&lt;/goal&gt;
                      &lt;/goals&gt;
                  &lt;/execution&gt;
              &lt;/executions&gt;
          &lt;/plugin&gt;
      &lt;/plugins&gt;
  &lt;/build&gt;
  
  &lt;dependencies&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework&lt;/groupId&gt;
          &lt;artifactId&gt;spring-context&lt;/artifactId&gt;
          &lt;version&gt;${spring-version}&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework&lt;/groupId&gt;
          &lt;artifactId&gt;spring-websocket&lt;/artifactId&gt;
          &lt;version&gt;${spring-version}&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;log4j&lt;/groupId&gt;
          &lt;artifactId&gt;log4j&lt;/artifactId&gt;
          &lt;version&gt;1.2.17&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;joda-time&lt;/groupId&gt;
          &lt;artifactId&gt;joda-time&lt;/artifactId&gt;
          &lt;version&gt;2.9.2&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;javax.websocket&lt;/groupId&gt;
          &lt;artifactId&gt;javax.websocket-api&lt;/artifactId&gt;
          &lt;version&gt;1.1&lt;/version&gt;
          &lt;scope&gt;provided&lt;/scope&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;javax.servlet&lt;/groupId&gt;
          &lt;artifactId&gt;javax.servlet-api&lt;/artifactId&gt;
          &lt;version&gt;3.1.0&lt;/version&gt;
          &lt;scope&gt;provided&lt;/scope&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.projectlombok&lt;/groupId&gt;
          &lt;artifactId&gt;lombok&lt;/artifactId&gt;
          &lt;version&gt;1.16.6&lt;/version&gt;
          &lt;scope&gt;provided&lt;/scope&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;com.google.guava&lt;/groupId&gt;
          &lt;artifactId&gt;guava&lt;/artifactId&gt;
          &lt;version&gt;19.0&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;com.google.code.gson&lt;/groupId&gt;
          &lt;artifactId&gt;gson&lt;/artifactId&gt;
          &lt;version&gt;2.5&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.apache.commons&lt;/groupId&gt;
          &lt;artifactId&gt;commons-lang3&lt;/artifactId&gt;
          &lt;version&gt;3.4&lt;/version&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;com.googlecode.zohhak&lt;/groupId&gt;
          &lt;artifactId&gt;zohhak&lt;/artifactId&gt;
          &lt;version&gt;1.1.1&lt;/version&gt;
          &lt;scope&gt;test&lt;/scope&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.mockito&lt;/groupId&gt;
          &lt;artifactId&gt;mockito-core&lt;/artifactId&gt;
          &lt;version&gt;1.10.19&lt;/version&gt;
          &lt;scope&gt;test&lt;/scope&gt;
          &lt;exclusions&gt;
              &lt;exclusion&gt;
                  &lt;artifactId&gt;hamcrest-core&lt;/artifactId&gt;
                  &lt;groupId&gt;org.hamcrest&lt;/groupId&gt;
              &lt;/exclusion&gt;
          &lt;/exclusions&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.springframework&lt;/groupId&gt;
          &lt;artifactId&gt;spring-test&lt;/artifactId&gt;
          &lt;version&gt;${spring-version}&lt;/version&gt;
          &lt;scope&gt;test&lt;/scope&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;junit&lt;/groupId&gt;
          &lt;artifactId&gt;junit&lt;/artifactId&gt;
          &lt;version&gt;4.12&lt;/version&gt;
          &lt;scope&gt;test&lt;/scope&gt;
          &lt;exclusions&gt;
              &lt;exclusion&gt;
                  &lt;groupId&gt;org.hamcrest&lt;/groupId&gt;
                  &lt;artifactId&gt;hamcrest-core&lt;/artifactId&gt;
              &lt;/exclusion&gt;
          &lt;/exclusions&gt;
      &lt;/dependency&gt;
      &lt;dependency&gt;
          &lt;groupId&gt;org.hamcrest&lt;/groupId&gt;
          &lt;artifactId&gt;hamcrest-all&lt;/artifactId&gt;
          &lt;version&gt;1.3&lt;/version&gt;
          &lt;scope&gt;test&lt;/scope&gt;
      &lt;/dependency&gt;
  &lt;/dependencies&gt;
  </code></pre>
  
  <p></p>
  
  <p>I've built this source at "clean package exec: Java" (Maven Goals)</p>
  
  <p>What do I have to do?
  I really want to fix it.</p>