mvn 打包带clean和不带clean区别（下）

protected boolean isUptodate()
        throws ArchiverException
    {
        final File zipFile = getDestFile();
        final long destTimestamp = zipFile.lastModified();
        if ( destTimestamp == 0 )
        {
            getLogger().debug( "isUp2date: false (Destination " + zipFile.getPath() + " not found.)" );
            return false; // File doesn't yet exist
        }
        final Iterator it = resources.iterator();
        if ( !it.hasNext() )
        {
            getLogger().debug( "isUp2date: false (No input files.)" );
            return false; // No timestamp to compare
        }
        while ( it.hasNext() )
        {
            final Object o = it.next();
            final long l;
            if ( o instanceof ArchiveEntry )
            {
                l = ( (ArchiveEntry) o ).getResource()
                                        .getLastModified();
            }
            else if ( o instanceof PlexusIoResourceCollection )
            {
                try
                {
                    l = ( (PlexusIoResourceCollection) o ).getLastModified();
                }
                catch ( final IOException e )
                {
                    throw new ArchiverException( e.getMessage(), e );
                }
            }
            else
            {
                throw new IllegalStateException( "Invalid object type: " + o.getClass()
                                                                            .getName() );
            }
            if ( l == PlexusIoResource.UNKNOWN_MODIFICATION_DATE )
            {
                // Don't know what to do. Safe thing is to assume not up2date.
                getLogger().debug( "isUp2date: false (Resource with unknown modification date found.)" );
                return false;
            }
            if ( l > destTimestamp )
            {
                getLogger().debug( "isUp2date: false (Resource with newer modification date found.)" );
                return false;
            }
        }
        getLogger().debug( "isUp2date: true" );
        return true;
    }