Memory leak using while uploading and downloading a file (may be because of using ChannelSftp.get( “file_name”) )?

Question

Can you please tell the internal working of ChannelSftp.get( "file_name")? Will the use of this function to get a single file from a list of files (600 files of 10 kb) can cause memory leakage issues in Tomcat8, if this function is used frequently?

This is the code which is used for uploading and fetching files from remote server.

public String connectRemote(String host, String user, String password, String 
    remotePath, String sFileName) throws IOException, JSchException, SftpException 
{
    try {
        String sFileNames ="";
        Session session = connectSFTP(host, user, password);

        Channel channel = session.openChannel("sftp");
        channel.connect();
        ChannelSftp chan = (ChannelSftp) channel;

        try {

            String ftpRemoteDirectory = "/Irismedical/Outbox_Eligibility";

            chan.cd(ftpRemoteDirectory);

            File ftest = new File(sFileName);

            chan.put(new FileInputStream(ftest), ftest.getName());

            sFileNames =  ftest.getName();

        }
        catch (Exception e) {
            chan.disconnect();
            session.disconnect();
            return null;
        }

        chan.cd("/Irismedical/Inbox/Eligibility");

        String sRes = null;
        for (int i = 0;i<6 ; i++) {

            try {
                  sRes = convertInputStreamToString(
                             chan.get(sFileNames+"_Response_271_1.edi"));

                 if (sRes  != null ) {

                     break;

            } catch (Exception e ) {
                if (i<3) {
                    Thread.sleep(3000);
                } else {
                    Thread.sleep(5000);
                }
            }
        }
                    session.disconnect();

        return sRes;
    }
    catch (Exception e) {
        }
        return null;
    }
}

private static String convertInputStreamToString(InputStream inputStream) 
    throws IOException {

    ByteArrayOutputStream result = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) != -1) {
        result.write(buffer, 0, length);
    }

    return result.toString(StandardCharsets.UTF_8.name());
}

Answer 1

You have to dispose the streams.

Both the FileInputStream in your upload code and the InputStream returned by ChannelSftp.get in your download code.

See Disposing streams in Java.