[FIXED] Why does the FTP download not work properly with Java

Issue

i'm currently working on a small checklist builder program in Java. I would like to upload and download the created file to my FTP Server (ftps). I'm using the following code for downloading:

public static void downloadfile(){
    FTPSClient con = null;

    System.out.println("Download Status: 5%");
    try
    {
        System.out.println("Download Status: 20%");
        con = new FTPSClient();
        con.connect(url);

        if (con.login(user, psw))
        {
            System.out.println("Download Status: 50%");
            con.enterLocalPassiveMode(); // important!
            con.setFileType(FTP.BINARY_FILE_TYPE);
            String data = "E:\\Downloads\\Testdokument.txt";

            OutputStream out = new FileOutputStream(new File(data));
            boolean result = con.retrieveFile("Testdokument.txt", out);
            out.close();
            System.out.println(result);
            if (result) {
                System.out.println("Download Status: 100%");
            } else if(result == false) {
                System.out.println("Download won't work");
            }
            con.logout();
            con.disconnect();
        }
    }
    catch (Exception e)
    {
        System.out.println("download failed");
        e.printStackTrace();
    }

}

the problem is that the download itself works fine. But the downloaded file is empty. If i try it with an Image it isn't "readable". The upload instead works perfectly. I use the Apache Common IO Library for the FTP function.

If i download the file the console shows first status 5%, 20%, 50% and than, after adding the false statement, Download won't work ...

I have no idea why the file itself is downloading but not including any content.

Any ideas?

Solution

You're not doing resources in java correctly.

Anytime you create an object that represents a resource, you must close it. You open a new FileOutputStream, and that is a resource. Anything that implements AutoCloseable is definitely a resource that you must close. Try this:

try (OutputStream out = new FileOutputStream(data /* no need to wrap in File */)) {
    // do your stuff with out here
}

Second note: Your exception handling is atrocious; please stop making this common mistake. Exceptions contain 4 useful bits of information: Type, Message, Trace, and Cause. You're literally tossing 3 out of the 4 into the bin. Just add throws Exception to your main method, and your downloadFile method. It saves you typing and makes your error messages much more useful.

Answered By - rzwitserloot

Answer Checked By - Cary Denson (PHPFixing Admin)