title: exec-maven-plugin Error in Spring-Roo Generated GWT Application
body: <p>I am trying to generate a simple gwt application using spring-roo. Following is the contents of log.roo file:</p>
  
  <pre><code>project --projectName erp --topLevelPackage org.erp
  persistence setup --provider HIBERNATE --database MYSQL 
  web gwt setup
  </code></pre>
  
  <p>After project generation, I run following command:</p>
  
  <pre><code>mvn clean package
  </code></pre>
  
  <p>And I receive following error:</p>
  
  <pre><code>[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2:exec 
  (default) on project erp: Command execution failed. Process exited with an 
  error: 255 (Exit value: 255) -&gt; [Help 1]
  </code></pre>
  
  <p>Following is the exec plugin configuration:</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;1.2&lt;/version&gt;
      &lt;executions&gt;
          &lt;execution&gt;
              &lt;phase&gt;process-classes&lt;/phase&gt;
              &lt;goals&gt;
                  &lt;goal&gt;exec&lt;/goal&gt;
              &lt;/goals&gt;
              &lt;configuration&gt;
                  &lt;id&gt;VerifyRequestFactoryInterfaces&lt;/id&gt;
                  &lt;executable&gt;java&lt;/executable&gt;
                  &lt;arguments&gt;
                      &lt;argument&gt;-cp&lt;/argument&gt;
                      &lt;classpath/&gt;
                      &lt;argument&gt;com.google.web.bindery.requestfactory.apt.ValidationTool&lt;/argument&gt;
                      &lt;argument&gt;${project.build.outputDirectory}&lt;/argument&gt;
                      &lt;argument&gt;${project.groupId}.client.managed.request.ApplicationRequestFactory&lt;/argument&gt;
                  &lt;/arguments&gt;
              &lt;/configuration&gt;
          &lt;/execution&gt;
      &lt;/executions&gt;
  &lt;/plugin&gt;
  </code></pre>
  
  <p>What does error 255 supposed to mean? What is the use of exec plugin in this scenario? And how can I overcome this error?</p>
  
  <p>Thanks...</p>