proxynewsdb.java

java高级使用教程 全书一共分六章

	// Is the names list the same as overviewFmt?
	if ( names != lastOkNames )
	    {
	    if ( ! Utils.equalsStrings( names, overviewFmt ) )
		return null;
	    lastOkNames = names;
	    }
	// Check that this group is one of ours.
	if ( group.getDbStamp() != dbStamp )
	    throw new NewsDbException( "mismatched database stamps" );
	// Do we need to refresh overview data for this group?
	long now = System.currentTimeMillis();
	long time = overviewCache.getLastTime( group );
	if ( time == -1 || now - time >= NnrpdUtils.INT_CHECKOVERVIEW )
	    {
	    readOverview( group );
	    overviewCache.setLastTime( group );
	    }
	// Now just get articles from the cache.
	int numArts = lastArtNum - firstArtNum + 1;
	String[][] results = new String[numArts][];
	// Check if we already have cached results for any of these articles.
	for ( int i = 0; i < numArts; ++i )
	    {
	    int artNum = firstArtNum + i;
	    results[i] = overviewCache.getEntry( group, artNum );
	    }
	return results;
	}

    private void readOverview( NewsDbGroup group ) throws NewsDbException
	{
	// Make sure it's the current group on the remote server.
	if ( currentGroup == null ||
	     ! group.getName().equals( currentGroup.getName() ) )
	    setGroup( group.getName() );
	// Do the XOVER command.
	pout.println(
	    NnrpdUtils.CMD_XOVER + " " +
	    group.getFirstArtNum() + "-" + group.getLastArtNum() );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 224:
	    while ( true )
		{
		String line;
		try
		    {
		    line = din.readLine();
		    }
		catch ( IOException e )
		    {
		    break;
		    }
		if ( line == null || line.equals( "." ) )
		    break;
		int tab = line.indexOf( '\t' );
		int artNum;
		try
		    {
		    artNum = Integer.parseInt( line.substring( 0, tab ) );
		    }
		catch ( NumberFormatException e )
		    {
		    continue;
		    }
		String[] overviewEntry =
		    Utils.splitStr( line.substring( tab + 1 ), '\t' );
		if ( overviewEntry.length != overviewFmt.length )
		    continue;	// ignore malformed lines
		overviewCache.addEntry( overviewEntry, group, artNum );
		}
	    break;
	    default:
	    throw new NewsDbException(
		"unexpected response to XOVER command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an enumeration of all the groups.
    // @exception NewsDbException if something goes wrong
    public Enumeration getGroups() throws NewsDbException
	{
	checkGroups();
	return groupTable.elements();
	}

    /// Get an enumeration of all groups created after a given time.
    // @exception NewsDbException if something goes wrong
    public synchronized Enumeration getGroups( long since ) throws NewsDbException
	{
	// Do the NEWGROUPS command.
	pout.println(
	    NnrpdUtils.CMD_NEWGROUPS + " " +
	    NnrpdUtils.rfc977DateTime( since ) );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 231:
	    return readGroups().elements();
	    default:
	    throw new NewsDbException(
		"unexpected response to NEWGROUPS command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an enumeration of all groups created after a given time that match
    // a given distributions pattern.
    // @exception NewsDbException if something goes wrong
    public synchronized Enumeration getGroups( long since, String distsPat ) throws NewsDbException
	{
	// Do the NEWGROUPS command.
	pout.println(
	    NnrpdUtils.CMD_NEWGROUPS + " " +
	    NnrpdUtils.rfc977DateTime( since ) + " " + distsPat );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 231:
	    return readGroups().elements();
	    default:
	    throw new NewsDbException(
		"unexpected response to NEWGROUPS command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Get an enumeration of all message-ids received after a given time
    // in groups matching the given pattern.
    // @exception NewsDbException if something goes wrong
    public Enumeration getMessageIds( String groupsPat, long since ) throws NewsDbException
	{
	// !!! This is purposely not implemented yet, because the NEWNEWS
	// command takes too long and would tie up the connection to the
	// remote server.  At some point I'll do an implementation which
	// opens up a second connection just for this one command.
	Vector messageIds = new Vector();
	return messageIds.elements();
	}

    /// Get an enumeration of all message-ids received after a given time
    // in groups matching the given pattern, that also match the
    // given distributions pattern.
    // @exception NewsDbException if something goes wrong
    public Enumeration getMessageIds( String groupsPat, long since, String distsPat ) throws NewsDbException
	{
	// !!! This is purposely not implemented yet, because the NEWNEWS
	// command takes too long and would tie up the connection to the
	// remote server.  At some point I'll do an implementation which
	// opens up a second connection just for this one command.
	Vector messageIds = new Vector();
	return messageIds.elements();
	}


    /// Post an article.
    // @exception NewsDbException if something goes wrong
    public synchronized void post( String artText ) throws NewsDbException
	{
	// Do the POST command.
	pout.println( NnrpdUtils.CMD_POST );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 340:
	    pout.print( artText );
	    pout.println( "." );
	    // Get and interpret results.
	    resp = readResp();
	    respNum = Utils.parseInt( resp[0], -1 );
	    switch ( respNum )
		{
		case 240:
		// Ok!
		break;
		case 441:
		throw new NewsDbException(
		    "post failed: " + Utils.flattenStrarr( resp ) );
		default:
		throw new NewsDbException(
		    "unexpected response to posted article: " +
		    Utils.flattenStrarr( resp ) );
		}
	    break;
	    default:
	    throw new NewsDbException(
		"unexpected response to POST command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Shut down the news database.
    public synchronized void close()
	{
	pout.println( NnrpdUtils.CMD_QUIT );
	try
	    {
	    din.close();
	    pout.flush();
	    pout.close();
	    socket.close();
	    }
	catch ( IOException ignore ) {}
	}


    /// Read a response from the server, and return it split into words.
    private synchronized String[] readResp() throws NewsDbException
	{
	pout.flush();
	String line;
	try
	    {
	    line = din.readLine();
	    }
	catch ( IOException e )
	    {
	    throw new NewsDbException(
		"problem reading remote response: " + e );
	    }
	if ( line == null || line.length() == 0 )
	    throw new NewsDbException( "problem reading remote response" );
	return Utils.splitStr( line );
	}

    /// Read the list of groups, if necessary.
    private synchronized void checkGroups() throws NewsDbException
	{
	checkGroupDescs();	// check group descriptions cache too
	long now = System.currentTimeMillis();
	if ( groupTable != null &&
	     now - groupsFetched < NnrpdUtils.INT_CHECKGROUPS )
	    return;
	// Do the LIST command.
	pout.println( NnrpdUtils.CMD_LIST );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 215:
	    groupTable = readGroups();
	    groupsFetched = now;
	    return;
	    default:
	    throw new NewsDbException(
		"unexpected response to LIST command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Read the list of groups descriptions, if necessary.
    private synchronized void checkGroupDescs() throws NewsDbException
	{
	long now = System.currentTimeMillis();
	if ( groupDescsTable != null &&
	     now - groupDescsFetched < NnrpdUtils.INT_CHECKGROUPDESCS )
	    return;
	// Do the LIST newsgroups command.
	pout.println( NnrpdUtils.CMD_LIST + " newsgroups" );
	// Get and interpret results.
	String[] resp = readResp();
	int respNum = Utils.parseInt( resp[0], -1 );
	switch ( respNum )
	    {
	    case 215:
	    groupDescsTable = new Hashtable();
	    String line, groupName, groupDesc;
	    int ws, nws;
	    while ( true )
		{
		try
		    {
		    line = din.readLine();
		    }
		catch ( IOException e )
		    {
		    break;
		    }
		if ( line == null || line.equals( "." ) )
		    break;
		ws = Utils.strCSpan( line, " \t" );
		nws = ws + Utils.strSpan( line, " \t", ws );
		groupName = line.substring( 0, ws );
		groupDesc = line.substring( nws );
		groupDescsTable.put( groupName, groupDesc );
		}
	    groupDescsFetched = now;
	    return;
	    default:
	    throw new NewsDbException(
		"unexpected response to LIST newsgroups command: " +
		Utils.flattenStrarr( resp ) );
	    }
	}

    /// Read a list of groups.
    private synchronized Hashtable readGroups() throws NewsDbException
	{
	Hashtable gt = new Hashtable();
	String line;
	String[] words;
	String groupName;
	int lastArtNum, firstArtNum;
	char flag;
	NewsDbGroup group;
	while ( true )
	    {
	    try
		{
		line = din.readLine();
		}
	    catch ( IOException e )
		{
		break;
		}
	    if ( line == null || line.equals( "." ) )
		break;
	    words = Utils.splitStr( line );
	    groupName = words[0];
	    try
		{
		lastArtNum = Integer.parseInt( words[1] );
		firstArtNum = Integer.parseInt( words[2] );
		}
	    catch ( NumberFormatException e )
		{
		continue;
		}
	    flag = words[3].charAt( 0 );
	    group = new NewsDbGroup(
		dbStamp, groupName, lastArtNum - firstArtNum + 1,
		firstArtNum, lastArtNum, flag,
		(String) groupDescsTable.get( groupName ) );
	    gt.put( group.getName(), group );
	    }
	return gt;
	}

    }