code: void checkJnlpConfig()
              throws MojoExecutionException
      {
          if ( jnlp == null )
          {
              throw new MojoExecutionException( "jnlp must be set to generate config!" );
          }
          JnlpFileType type = jnlp.getType();
          if ( type == null )
          {
              throw new MojoExecutionException( "jnlp must define a default jnlp type file to generate (among " +
                                                        Arrays.toString( JnlpFileType.values() ) + " )." );
          }
          if ( !type.isRequireMainClass() && StringUtils.isNotBlank( jnlp.getMainClass() ) )
          {
              getLog().warn( "Jnlp file of type '" + type +
                                     "' does not support mainClass, value will not be accessible in template." );
              jnlp.setMainClass( null );
              
              addApplicationFile = false;
          }
      }
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