Send SFTP file from database without actually creating a file

Question

I want to send some data from the database. Currently our SFTP is set up like so (using the apache commons vsf2 library).

    try(StandardFileSystemManager manager = new StandardFileSystemManager())
        File file = generateFileFromDatabase();
        manager.init();
   
        FileSystemOptions opts = new FileSystemOptions();
        SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(
                opts, "no");
        SftpFileSystemConfigBuilder.getInstance().setUserDirIsRoot(opts, true);
        SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, 10000);

        // Create localfile object
        FileObject localFile = manager.resolveFile(file.getAbsolutePath());

        // Create remote file object
        FileObject remoteFile = manager.resolveFile(sftpUri, opts);

        // Copy local file to sftp server
        remoteFile.copyFrom(localFile, Selectors.SELECT_SELF);


    } catch (Exception ex) {
        ex.printStackTrace();
    }

However, generateFileFromDatabase() works by invoking the new keyword, as in

       return new File();

I don't want this, because this saves a new file in the file system every time generateFileFromDatabase() is called. Is there a way to generate a File() without saving it to the file directory?

Answer 1

Just use

OutputStream os = remoteFile.getContent().getOutputStream();

and then write In a loop to it, just like you would with a local file.

This might be a problem for slow reading/large transfers with long open connections. In that case you might need to pre-produce chunks and write them in multiple appends.