code: public void check( JnlpDependencyConfig config )
      {
          if ( config == null )
          {
              throw new NullPointerException( "config can't be null" );
          }
          if ( config.getArtifact() == null )
          {
              throw new NullPointerException( "config.artifact can't be null" );
          }
          if ( config.getArtifact().getFile() == null )
          {
              throw new NullPointerException( "config.artifact.file can't be null" );
          }
          if ( !config.isSign() )
          {
              throw new IllegalStateException( "Can't sign if config.isSign is false" );
          }
  
          File file = config.getArtifact().getFile();
  
          boolean jarSigned;
          try
          {
              jarSigned = signTool.isJarSigned( file );
          }
          catch ( MojoExecutionException e )
          {
              throw new RuntimeException( e.getMessage(), e.getCause() );
          }
  
          if ( jarSigned && !config.isCanUnsign() )
          {
              throw new IllegalStateException( "Can't unsign the config.artifact.file if config.isCanUsign is false" );
          }
      }
docs: {@inheritDoc}