将blob转换回原始文件类型并使其可供下载

所以我有一个使用HTML5和JavaScript构建的客户端应用程序。 我的应用程序调用Web服务（使用c＃构建），它从MySql数据库中提取blob数据并将其传递给客户端应用程序。

这个blob数据实际上是一个存储在MySQL数据库中的小文件（小于100kb）。 我希望我的客户端应用程序能够将此blob转换回其原始文件类型，然后询问用户是否有下载权限。 现在我想知道这是不是一个好主意？ 或者我应该只是在我的Web服务中进行文件转换，然后将文件本身发送到JSP应用程序？

任何帮助/建议将受到高度赞赏！ 如果你有任何好的教程/代码，这可能有助于我的转换，那么请在这里发布作为答案？ 提前致谢！

Answer 1

使用此示例并将SQL数据库更改为您的数据库以及Select语句

SqlConnection pubsConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=pubs;"); SqlCommand logoCMD = new SqlCommand("SELECT pub_id, logo FROM pub_info", pubsConn); FileStream fs; // Writes the BLOB to a file (*.bmp). BinaryWriter bw; // Streams the BLOB to the FileStream object. int bufferSize = 100; // Size of the BLOB buffer. byte[] outbyte = new byte[bufferSize]; // The BLOB byte[] buffer to be filled by GetBytes. long retval; // The bytes returned from GetBytes. long startIndex = 0; // The starting position in the BLOB output. string pub_id = ""; // The publisher id to use in the file name. // Open the connection and read data into the DataReader. pubsConn.Open(); SqlDataReader myReader = logoCMD.ExecuteReader(CommandBehavior.SequentialAccess); while (myReader.Read()) { // Get the publisher id, which must occur before getting the logo. pub_id = myReader.GetString(0); // Create a file to hold the output. fs = new FileStream("logo" + pub_id + ".bmp", FileMode.OpenOrCreate, FileAccess.Write); bw = new BinaryWriter(fs); // Reset the starting byte for the new BLOB. startIndex = 0; // Read the bytes into outbyte[] and retain the number of bytes returned. retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize); // Continue reading and writing while there are bytes beyond the size of the buffer. while (retval == bufferSize) { bw.Write(outbyte); bw.Flush(); // Reposition the start index to the end of the last buffer and fill the buffer. startIndex += bufferSize; retval = myReader.GetBytes(1, startIndex, outbyte, 0, bufferSize); } // Write the remaining buffer. bw.Write(outbyte, 0, (int)retval - 1); bw.Flush(); // Close the output file. bw.Close(); fs.Close(); } // Close the reader and the connection. myReader.Close(); pubsConn.Close();