code: @Override
      protected List<ChecksumFile> getFilesToProcess()
      {
          List<ChecksumFile> files = new LinkedList<ChecksumFile>();
  
          // Add project main artifact.
          if ( hasValidFile( project.getArtifact() ) )
          {
              files.add( new ChecksumFile( "", project.getArtifact().getFile(), project.getArtifact().getType(),null ) );
          }
  
          // Add projects attached.
          if ( project.getAttachedArtifacts() != null )
          {
              for ( Artifact artifact : (List<Artifact>) project.getAttachedArtifacts() )
              {
                  if ( hasValidFile( artifact ) )
                  {
                      files.add( new ChecksumFile( "", artifact.getFile(), artifact.getType(), artifact.getClassifier() ) );
                  }
              }
          }
          return files;
      }
docs: Build the list of files from which digests should be generated.
  
  <p>The list is composed of the project main and attached artifacts.</p>
  
  @return the list of files that should be processed.
  @see #hasValidFile(org.apache.maven.artifact.Artifact)