[Flutter] unable to download pdf from mariadb using flutter

I am having a hard time downloading a pdf from mariadb. I can download the json file without any issues.

This is what I see in the Mariadb database. I am storing the attachment data in a longblob.

SELECT sys_data FROM sys_attachment_data; +---------------------------------------------------------------------------------------------------+ | sys_data | +---------------------------------------------------------------------------------------------------+ | (16)[123, 34, 110, 97, 109, 101, 34, 58, 34, 74, 85, 65, 78, 34, 125, 10] | | (11702)[37, 80, 68, 70, 45, 49, 46, 52, 10, 37, 211, 235, 233, 225, 10, 49, 32, 48, 32, 111, ...] | +---------------------------------------------------------------------------------------------------+

I think I am storing a byte array but I am not sure why there is a (16) and (11702) in front of the data.

for some reason my app does not like downloading longblob, so I had to change the method in my server to get the data from the database. this is the method that fetches the data from the database::


public static Map<String, Object> get_records(String query_string) {
List<Map<String, Object>> results = new ArrayList<>();

try (Connection connection = data_source.getConnection();
PreparedStatement statement = connection.prepareStatement(query_string)) {

ResultSet resultSet = statement.executeQuery();
ResultSetMetaData metaData = resultSet.getMetaData();
int columnCount = metaData.getColumnCount();

while (resultSet.next()) {
Map<String, Object> record = new HashMap<>();
for (int i = 1; i <= columnCount; i++) {
String columnLabel = metaData.getColumnLabel(i);
Object columnValue;

// Check if the column is a BLOB and handle it accordingly
if (metaData.getColumnType(i) == java.sql.Types.BLOB || metaData.getColumnType(i) == java.sql.Types.LONGVARBINARY) {
byte[] blobData = resultSet.getBytes(i);
if (blobData != null) {
columnValue = Base64.getEncoder().encodeToString(blobData); // Encode the byte array as Base64
} else {
columnValue = null; // If blob data is null
}
} else {
// Handle other column types
columnValue = resultSet.getObject(i);
}

record.put(columnLabel, columnValue);
}
results.add(record);
}

resultSet.close();
} catch (SQLException e) {
return Map.of("error", "unable to process request");
}

return Map.of("records", results);
}





Below is the code in flutter that I use to get the data from the server and to download the file.

code::



static Future<void> download_form_attachment(String attachment_id) async {
print("Starting download for attachment_id: $attachment_id");


List<Map<String, dynamic>> attachment_datas = globalProviderContainer.read(form_page_provider.notifier).state.sys_attachment_data.where((element) => element['sys_attachment_id'] == attachment_id).toList();

Map<String, dynamic> attachment = globalProviderContainer.read(form_page_provider.notifier).state.sys_attachment.firstWhere((element) => element['sys_id'] == attachment_id);
attachment_datas.sort((a, b) => a['sys_order'].compareTo(b['sys_order']));

if (attachment_datas.isEmpty) {

}

print("Attachment type: ${attachment['sys_type']}");
print("Attachment name: ${attachment['sys_name']}");
String joined_data = attachment_datas.map((data) => data['sys_data']).join();
print("joined_data (Base64 encoded): ${joined_data}");

// Decode the base64 encoded data
List<int> bytes = base64Decode(joined_data);
String rawString = String.fromCharCodes(bytes);

print("Decoded bytes: ${bytes}");

try {
if (attachment['sys_type'] == 'json') {
// Convert bytes to string
print("Raw string: $rawString");

// Extract the actual byte values
RegExp regex = RegExp(r'\[([^\]]+)\]');
Match? match = regex.firstMatch(rawString);

if (match != null) {
String byteString = match.group(1)!;
List<int> actualBytes = byteString.split(', ').map(int.parse).toList();

// Convert actual bytes to string
String jsonString = String.fromCharCodes(actualBytes);
print("JSON string: $jsonString");

// Parse the JSON string
dynamic jsonData = json.decode(jsonString);
// print("Parsed JSON data: $jsonData");

final blob = html.Blob([jsonData], 'application/json');

// Set the correct file name using sys_name from the attachment
String fileName = '${attachment['sys_name']}';
print("file_name: ${fileName}");

// Create a download link
final url = html.Url.createObjectUrlFromBlob(blob);
final anchor = html.AnchorElement(href: url)
..setAttribute('download', fileName)
..click(); // Trigger the download

// Clean up the URL after the download
html.Url.revokeObjectUrl(url);
} else {
print("Failed to extract byte values from the string");
}
} else if (attachment['sys_type'] == 'pdf') {
// Convert the bytes to a Blob
final blob = html.Blob([bytes], 'application/pdf');

// Set the correct file name using sys_name from the attachment
String fileName = '${attachment['sys_name']}';
print("file_name: ${fileName}");

// Create a download link
final url = html.Url.createObjectUrlFromBlob(blob);
final anchor = html.AnchorElement(href: url)
..setAttribute('download', fileName)
..click(); // Trigger the download

// Clean up the URL after the download
html.Url.revokeObjectUrl(url);
} else {
print("Unhandled file type: ${attachment['sys_type']}");
}
} catch (e) {
print("Error during file processing: $e");
}
}





This is the output I see::

try to download
Starting download for attachment_id: 7dab2151-a826-46c4-b3c2-2ef843112f65_1728001280274
No attachment data found, fetching from database
Attachment type: pdf
Attachment name: sample_pdf.pdf
joined_data (Base64 encoded): KDExNzAyKVszNywgODAsIDY4LCA3MCwgNDUsIDQ5LCA0NiwgNTIsIDEwLCAzNywgMjExLCAyMzUsIDIzMywgMjI1LCAxMCwgNDksIDMyLCA0OCwgMzIsIDExMSwgLi4uXQ==
Decoded bytes: [40, 49, 49, 55, 48, 50, 41, 91, 51, 55, 44, 32, 56, 48, 44, 32, 54, 56, 44, 32, 55, 48, 44, 32, 52, 53, 44, 32, 52, 57, 44, 32, 52, 54, 44, 32, 53, 50, 44, 32, 49, 48, 44, 32, 51, 55, 44, 32, 50, 49, 49, 44, 32, 50, 51, 53, 44, 32, 50, 51, 51, 44, 32, 50, 50, 53, 44, 32, 49, 48, 44, 32, 52, 57, 44, 32, 51, 50, 44, 32, 52, 56, 44, 32, 51, 50, 44, 32, 49, 49, 49, 44, 32, 46, 46, 46, 93]
file_name: sample_pdf.pdf


The pdf downloads but when I open the pdf I see this::



I didnt see any stackoverflows that were exactly what I was looking for.





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