Method downloadUrlSafely

CodenameOne/src/com/codename1/io/Util.java:3157–3259

(String url, final String fileName, final OnComplete<Integer> percentageCallback, final OnComplete<String> filesavedCallback)

    ///
    /// - `IOException`
    public static void downloadUrlSafely(String url, final String fileName, final OnComplete<Integer> percentageCallback, final OnComplete<String> filesavedCallback) throws IOException {
        // Code discussion here: https://stackoverflow.com/a/62137379/1277576
        String partialDownloadsDir = FileSystemStorage.getInstance().getAppHomePath() + FileSystemStorage.getInstance().getFileSystemSeparator() + "partialDownloads";
        if (!FileSystemStorage.getInstance().isDirectory(partialDownloadsDir)) {
            FileSystemStorage.getInstance().mkdir(partialDownloadsDir);
        }
        final String uniqueId = url.hashCode() + "" + downloadUrlSafelyRandom.nextInt(); // do its best to be unique if there are parallel downloads
        final String partialDownloadPath = partialDownloadsDir + FileSystemStorage.getInstance().getFileSystemSeparator() + uniqueId;
        final boolean isStorage = fileName.indexOf("/") < 0; // as discussed here: https://stackoverflow.com/a/57984257
        final long fileSize = getFileSizeWithoutDownload(url, true); // total expected download size, with a check partial download support
        final int splittingSize = 512 * 1024; // 512 kbyte, size of each small download
        final Wrapper<Long> downloadedTotalBytes = new Wrapper<Long>(0l);
        final OutputStream out; //NOPMD CloseResource - stream closed when download completes
        if (isStorage) {
            out = Storage.getInstance().createOutputStream(fileName); // leave it open to append partial downloads
        } else {
            out = FileSystemStorage.getInstance().openOutputStream(fileName);
        }
        final EasyThread mergeFilesThread = EasyThread.start("mergeFilesThread"); // Codename One thread that supports crash protection and similar Codename One features.

        final ConnectionRequest cr = new GZConnectionRequest();
        cr.setUrl(url);
        cr.setPost(false);
        if (fileSize > splittingSize) {
            // Which byte should the download start from?
            cr.addRequestHeader("Range", "bytes=0-" + splittingSize);
            cr.setDestinationFile(partialDownloadPath);
        } else {
            Util.cleanup(out);
            if (isStorage) {
                cr.setDestinationStorage(fileName);
            } else {
                cr.setDestinationFile(fileName);
            }
        }
        cr.addResponseListener(new ActionListener<NetworkEvent>() {
            @Override
            public void actionPerformed(NetworkEvent evt) {
                mergeFilesThread.run(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            // We append the just saved partial download to the fileName, if it exists
                            if (FileSystemStorage.getInstance().exists(partialDownloadPath)) {
                                InputStream in = null; //NOPMD CloseResource
                                try {
                                    in = FileSystemStorage.getInstance().openInputStream(partialDownloadPath);
                                    Util.copyNoClose(in, out, 8192);
                                } finally {
                                    Util.cleanup(in);
                                }
                                // before deleting the file, we check and update how much data we have actually downloaded
                                downloadedTotalBytes.set(downloadedTotalBytes.get() + FileSystemStorage.getInstance().getLength(partialDownloadPath));
                                FileSystemStorage.getInstance().delete(partialDownloadPath);
                            }
                            // Is the download finished?
                            if (downloadedTotalBytes.get() > fileSize) {
                                throw new IllegalStateException("More content has been downloaded than the file length, check the code.");