public void execute()

in core/src/main/java/org/apache/ftpserver/command/impl/RETR.java [66:218]
114 lines of code
15 McCabe index (conditional complexity)

    public void execute(final FtpIoSession session,
            final FtpServerContext context, final FtpRequest request)
            throws IOException, FtpException {

        try {

            // get state variable
            long skipLen = session.getFileOffset();

            // argument check
            String fileName = request.getArgument();
            if (fileName == null) {
                session.write(LocalizedDataTransferFtpReply.translate(
                                        session,
                                        request,
                                        context,
                                        FtpReply.REPLY_501_SYNTAX_ERROR_IN_PARAMETERS_OR_ARGUMENTS,
                                        "RETR", null, null));
                return;
            }

            // get file object
            FtpFile file = null;
            try {
                file = session.getFileSystemView().getFile(fileName);
            } catch (Exception ex) {
                LOG.debug("Exception getting file object", ex);
            }
            if (file == null) {
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_550_REQUESTED_ACTION_NOT_TAKEN,
                        "RETR.missing", fileName, file));
                return;
            }
            fileName = file.getAbsolutePath();

            // check file existance
            if (!file.doesExist()) {
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_550_REQUESTED_ACTION_NOT_TAKEN,
                        "RETR.missing", fileName, file));
                return;
            }

            // check valid file
            if (!file.isFile()) {
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_550_REQUESTED_ACTION_NOT_TAKEN,
                        "RETR.invalid", fileName, file));
                return;
            }

            // check permission
            if (!file.isReadable()) {
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_550_REQUESTED_ACTION_NOT_TAKEN,
                        "RETR.permission", fileName, file));
                return;
            }

            // 24-10-2007 - added check if PORT or PASV is issued, see
            // https://issues.apache.org/jira/browse/FTPSERVER-110
            //TODO move this block of code into the super class. Also, it makes 
            //sense to have this as the first check before checking everything 
            //else such as the file and its permissions.  
            DataConnectionFactory connFactory = session.getDataConnection();
            if (connFactory instanceof IODataConnectionFactory) {
                InetAddress address = ((IODataConnectionFactory) connFactory)
                        .getInetAddress();
                if (address == null) {
                    session.write(new DefaultFtpReply(
                            FtpReply.REPLY_503_BAD_SEQUENCE_OF_COMMANDS,
                            "PORT or PASV must be issued first"));
                    return;
                }
            }

            // get data connection
            session.write(LocalizedFtpReply.translate(session, request, context,
                    FtpReply.REPLY_150_FILE_STATUS_OKAY, "RETR", null));

            // send file data to client
            boolean failure = false;
            InputStream is = null;

            DataConnection dataConnection;
            try {
                dataConnection = session.getDataConnection().openConnection();
            } catch (Exception e) {
                LOG.debug("Exception getting the output data stream", e);
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_425_CANT_OPEN_DATA_CONNECTION, "RETR",
                        null, file));
                return;
            }

            long transSz = 0L;
            try {

                // open streams
                is = openInputStream(session, file, skipLen);

                // transfer data
                transSz = dataConnection.transferToClient(session.getFtpletSession(), is);
                // attempt to close the input stream so that errors in 
                // closing it will return an error to the client (FTPSERVER-119) 
                if(is != null) {
                    is.close();
                }

                LOG.info("File downloaded {}", fileName);

                // notify the statistics component
                ServerFtpStatistics ftpStat = (ServerFtpStatistics) context
                        .getFtpStatistics();
                if (ftpStat != null) {
                    ftpStat.setDownload(session, file, transSz);
                }
                
            } catch (SocketException ex) {
                LOG.debug("Socket exception during data transfer", ex);
                failure = true;
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_426_CONNECTION_CLOSED_TRANSFER_ABORTED,
                        "RETR", fileName, file, transSz));
            } catch (IOException ex) {
                LOG.debug("IOException during data transfer", ex);
                failure = true;
                session
                        .write(LocalizedDataTransferFtpReply
                                .translate(
                                        session,
                                        request,
                                        context,
                                        FtpReply.REPLY_551_REQUESTED_ACTION_ABORTED_PAGE_TYPE_UNKNOWN,
                                        "RETR", fileName, file, transSz));
            } finally {
                // make sure we really close the input stream
                IoUtils.close(is);
            }

            // if data transfer ok - send transfer complete message
            if (!failure) {
                session.write(LocalizedDataTransferFtpReply.translate(session, request, context,
                        FtpReply.REPLY_226_CLOSING_DATA_CONNECTION, "RETR",
                        fileName, file, transSz));

            }
        } finally {
            session.resetState();
            session.getDataConnection().closeDataConnection();
        }
    }