Converted byteArray data to PDF not opening

Question

I am reading data from a CSV file and saving it to a Map object called 'record'. I am trying to convert the blob data from the record object and save the data to its document file. I have tested for image documents and they convert & save fine to files that can be opened. However, the pdf images after saving, do not open and return an error instead.

private static void convertBlobToBase64(Map<String, Object> record) {
        boolean blob = record.keySet().stream().anyMatch(key -> key.contains("Blob"));

        if (blob) {
            for (Map.Entry<String, Object> entry : record.entrySet()) {
                if (entry.getKey().contains("Blob")) {
                    try {
                        String hexData = (String) entry.getValue();
                        hexData = hexData.substring(1).replaceAll("[^0-9A-Fa-f]", "");
                        if (hexData.length() % 2 != 0) {
                            throw new IllegalArgumentException("Invalid hex string");
                        }
                        byte[] hexBinary = DatatypeConverter.parseHexBinary(hexData);
                        String base64String = Base64.getEncoder().encodeToString(hexBinary);
                        blobToDoc(base64String, (String) record.get("Document_FileName"));
                    } catch (IOException | SQLException e) {
                        throw new RuntimeException("Error converting blob:  "+ e.getMessage());
                    }
                    return;
                }
            }
        }
    }

    private static void blobToDoc(String blobData, String fileName) throws SQLException, IOException {
        byte[] blobValue = Base64.getDecoder().decode(blobData);
        Blob blob = new SerialBlob(blobValue);
        String path = "src/main/resources/" + fileName;
        Path outputFile = Paths.get(path);
        try (OutputStream outputStream = Files.newOutputStream(outputFile)) {
            byte[] buffer = new byte[4096];
            int bytesRead = -1;
            InputStream inputStream = blob.getBinaryStream();
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
            inputStream.close();
            outputStream.flush();
        }
    }

This is the error that comes up when opening the saved PDFs:

Please, how can I fix this?

I took the blob data to an online tool to convert first to base64 and then to pdf. It complained about being unable to convert 'application/octet-stream' to 'application/pdf'. Is there a way to convert the octet-stream data to readable pdf file?

Answer 1

I found that the initial base64 string gotten from the blob data is still an encoded string and that it required a bit extra step to show the original pdf contents:

private static void pdfBlobToDoc(String blobData, String fileName) {
    String path = "src/main/resources/" + fileName;

    try (FileOutputStream fos = new FileOutputStream(path)) {
        byte[] blobValue = Base64.getDecoder().decode(blobData.replaceAll("[^A-Za-z0-9+/=]", ""));
        Blob blob = new SerialBlob(blobValue);
        fos.write(blob.getBytes(1, (int) blob.length()));
    } catch (Exception e) {
        throw new RuntimeException("Error writing pdf blob to " + fileName + ": " + e.getMessage());
    }
}

With this, I am able to read the pdf documents properly.