从 Oracle 数据库中检索 blob pdf 文件，为其添加密码并更新数据库中的 blob 列

Question

My case is:

1. Retrieve blob file from Oracle database which is a pdf file
2. Add password to retrieved pdf file
3. Update the record on the Oracle database which is the same blob column.

That's what i did but I'm not sure if that's ok... I would be very grateful for any help with that...

public Stream encryptPdf(int id_file)
        {

            string connStr = "User Id=user; Password=pass; Data Source=oracle; Pooling=false";
            
            OracleConnection con = new OracleConnection(connStr);
            try
            {
                con.Open();
            }
            catch (OracleException ex)
            {
               throw new Exception(ex.Message);
            }

            string sql = "select blob from table";
            

            OracleCommand cmd = new OracleCommand(sql, con);

            cmd.InitialLOBFetchSize = 8192;

            OracleDataReader dr = cmd.ExecuteReader();

            try
            {
                dr.Read();
            }
            catch (OracleException ex)
            {
                throw new Exception(ex.Message);
            }

            OracleBlob blob = dr.GetOracleBlob(0);

            MemoryStream ms = new MemoryStream();           
            ms.Write(blob.Value, 0, blob.Value.Length);


            PdfDocument document = PdfReader.Open(ms);
            PdfSecuritySettings securitySettings = document.SecuritySettings;
            securitySettings.UserPassword = "user";
            securitySettings.OwnerPassword = "12345";
            securitySettings.PermitAccessibilityExtractContent = false;
            securitySettings.PermitAnnotations = false;
            securitySettings.PermitAssembleDocument = false;
            securitySettings.PermitExtractContent = false;
            securitySettings.PermitFormsFill = true;
            securitySettings.PermitFullQualityPrint = false;
            securitySettings.PermitModifyDocument = true;
            securitySettings.PermitPrint = false;

            //BinaryReader binaryReader = new BinaryReader(ms);
            //byte[] data = binaryReader.ReadBytes((int)ms.Length);

            document.Save(ms);            
            ms.Close();
           
            return ms;
        }

I was thinking that MemoryStream would be a good solution but right now I just don't know what do:(

Answer 1

I was able to get the effect of reading the blob and updating it to add a password to the pdf file.

The only thing that is currently worrying is that the speed of this method is very slow. Maybe you would have some tip on how to speed it up?

     public Stream encryptPdf(int id)
    {

        string constr = "User Id=user;Password=pass;Data Source=test";
        OracleConnection con = new OracleConnection(constr);
        con.Open();
        
        // Get the ByteCodes for blob file
        string cmdstr = string.Format(@"select blob_file from table where blob = {0}", id);            
        OracleCommand cmd = new OracleCommand(cmdstr, con);

        // Since we are going to update the OracleBlob object, we will
        //have to create a transaction
        OracleTransaction txn = con.BeginTransaction();

        // Get the reader
        OracleDataReader reader = cmd.ExecuteReader();

        // Declare the variables to retrieve the data in EmpInfo
        OracleBlob byteCodesBlob;

        // Read the first row
        reader.Read();
        if (!reader.IsDBNull(0))
        {
            byteCodesBlob = reader.GetOracleBlobForUpdate(0);

            PdfDocument document = PdfReader.Open(byteCodesBlob);
            PdfSecuritySettings securitySettings = document.SecuritySettings;
            securitySettings.UserPassword = "user";
            securitySettings.OwnerPassword = "1234";
            securitySettings.PermitAccessibilityExtractContent = false;
            securitySettings.PermitAnnotations = false;
            securitySettings.PermitAssembleDocument = false;
            securitySettings.PermitExtractContent = false;
            securitySettings.PermitFormsFill = true;
            securitySettings.PermitFullQualityPrint = false;
            securitySettings.PermitModifyDocument = true;
            securitySettings.PermitPrint = false;

            document.Save(byteCodesBlob);
            
            // Close the reader
            reader.Close();

            // Update the ByteCodes object
            BinaryReader binaryReader = new BinaryReader(byteCodesBlob);
            byte[] data = binaryReader.ReadBytes((int)byteCodesBlob.Length);
            
            byteCodesBlob.Append(data, 0, data.Length);

            // Now commit the transaction
            txn.Commit();
            Console.WriteLine("Blob Column successfully updated");
        }
        else
            reader.Dispose();

        // Close the connection
        con.Dispose();
        return null;
    }