(Java) SFTP Upload Large File in Parts

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Demonstrates how to split a large file into N parts and then upload each part separately. This technique can be used to potentially avoid limits a SFTP server might impose on upload file size.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkSFtp sftp = new CkSFtp();

    // Set some timeouts, in milliseconds:
    sftp.put_ConnectTimeoutMs(5000);
    sftp.put_IdleTimeoutMs(10000);

    // Connect to the SSH server.  
    // The standard SSH port = 22
    // The hostname may be a hostname or IP address.
    String hostname = "sftp.example.com";
    int port = 22;
    boolean success = sftp.Connect(hostname,port);
    if (success != true) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    // Authenticate with the SSH server.  Chilkat SFTP supports
    // both password-based authenication as well as public-key
    // authentication.  This example uses password authenication.
    success = sftp.AuthenticatePw("myLogin","myPassword");
    if (success != true) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    // After authenticating, the SFTP subsystem must be initialized:
    success = sftp.InitializeSftp();
    if (success != true) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    // Open a remote file for writing on the SSH server.
    // If the file already exists, it is overwritten.
    // (Specify "createNew" instead of "createTruncate" to
    // prevent overwriting existing files.)
    String handle = sftp.openFile("big.zip","writeOnly","createTruncate");
    if (sftp.get_LastMethodSuccess() != true) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    // We're going to upload the local file "qa_data/zips/big.zip" (a relative local path from our current working directory)
    // to the SFTP server.
    String localFilePath = "qa_data/zips/big.zip";

    // Rather than uploading in one shot, we'll read the local file in chunks
    // and upload a chunk at a time.
    CkFileAccess fac = new CkFileAccess();

    success = fac.OpenForRead(localFilePath);
    if (success == false) {
        sftp.CloseHandle(handle);
        System.out.println(fac.lastErrorText());
        return;
        }

    // If we were to split the local file into 128K chunks, how many chunks (blocks) would
    // we have, including the last partial block?
    int blockSize = 131072;
    int numBlocks = fac.GetNumBlocks(blockSize);
    System.out.println("Number of blocks = " + numBlocks);

    CkBinData bd = new CkBinData();
    int i = 0;
    while (i < numBlocks) {
        // Read the Nth block, which gets appended to the bd.  (which means
        // we must clear the contents of bd before the next iteration)
        success = fac.ReadBlockBd(i,blockSize,bd);
        if (success == false) {
            sftp.CloseHandle(handle);
            System.out.println(fac.lastErrorText());
            return;
            }

        // Upload this block to the open remote file.
        success = sftp.WriteFileBd(handle,bd);
        if (success == false) {
            System.out.println(sftp.lastErrorText());
            return;
            }

        // Clear the contents for the next iteration.
        bd.Clear();

        i = i+1;
        }

    // Close the local file.
    fac.FileClose();

    // -----------------------------------------------------------------------------
    // This is important.  You must close the handle on the server.
    // Otherwise open handles will accumulate on the server until eventually a limit
    // is reached and the server will fail on a call to OpenFile.
    // -----------------------------------------------------------------------------

    // Close the remote file handle on the server.
    success = sftp.CloseHandle(handle);
    if (success != true) {
        System.out.println(sftp.lastErrorText());
        return;
        }

    System.out.println("Success.");
  }
}