maven 在执行package,install,deploy时使用clean与不使用clean的不同之处

<project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0

http://maven.apache.org/xsd/maven-4.0.0.xsd">

  ...
  <packaging>war</packaging>
  ...
</project>

 protected boolean checkForced()
        throws ArchiverException
    {
        if ( !isForced() && isSupportingForced() && isUptodate() )
        {
            getLogger().debug( "Archive " + getDestFile() + " is uptodate." );
            return false;
        }
        return true;
    }

 protected void execute()
        throws ArchiverException, IOException
    {
        if ( ! checkForced() )
        {
            return;
        }

        if ( doubleFilePass )
        {
            skipWriting = true;
            createArchiveMain();
            skipWriting = false;
            createArchiveMain();
        }
        else
        {
            createArchiveMain();
        }

        finalizeZipOutputStream( zOut );
    }

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;
    }