Java Apache FTPClient most downloaded files are empty or missing

Question

This is my code that is supposed to download entire FTP directory to a local folder. It does it well, but most of the files are 0KB in size. Only JSON files seem to contain all their data.

Things I tried:

1. Changing FTP file type with client.setFileType("FTP.BINARY_FILE_TYPE");
2. Using OutputStream instead of FileOutputStream

Code:

public static void copyFolder(File destination, FTPFile sourceFile, FTPClient ftpClient) throws IOException{
    if (!sourceFile.isDirectory()) {
        //copy file
        File downloadFile = new File(destination + "/"+ sourceFile.getName());
        String remoteFile =  sourceFile.getName();
        FileOutputStream outputStream = new FileOutputStream(downloadFile);
        System.out.println(remoteFile);
        System.out.println(downloadFile.getPath());
        boolean success = ftpClient.retrieveFile(remoteFile, outputStream);
        if(success) {
            System.out.println("Retrieved " + remoteFile);
        }
        outputStream.close();
    }else{
        //loop through a subdirectory
        ftpClient.changeWorkingDirectory(ftpClient.printWorkingDirectory() + "/" + sourceFile.getName());
        System.out.println(ftpClient.printWorkingDirectory());
        FTPFile[] contents = ftpClient.listFiles(ftpClient.printWorkingDirectory());
        File newDest = new File(destination + "/" + sourceFile.getName());
        if(!newDest.exists()){
            newDest.mkdir();
        }
        for(FTPFile file : contents){
            copyFolder(newDest, file, ftpClient);
        }
        return;
    }
}

How to get the transfer correctly?

• log from ftp

• tree of the ftp directory

• tree of downloading directory

Trying to download it on the same computer ended with losing connection a few times - between and during file downloads. Also it seems that few files are downloaded. I will change the title of question to be more specific.

Only two files are being copied for some reason – https://pastebin.com/XNWqRMDj They are not empty.

Answer 1

The problem is your changeWorkingDirectory call. It's failing most of the time.

ftpClient.changeWorkingDirectory(ftpClient.printWorkingDirectory() + "/" + sourceFile.getName());

It should be:

ftpClient.changeWorkingDirectory(destination + "/" + sourceFile.getName());

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For a complete working code for downloading FTP folders in Java, see:
Download all folders recursively from FTP server in Java