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),该服务从 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 数据实际上是一个小文件(小于 100kb),存储在 MySQL 数据库中。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,然后向用户询问下载权限。现在我想知道这是不是一个好主意?或者我应该简单地在我的 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/建议将不胜感激!如果您有任何好的教程/代码,这可能会帮助我进行转换,那么请将它们张贴在这里作为答案?提前致谢!
最佳答案
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();
关于c# - 将 blob 转换回原始文件类型并使其可供下载,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8592455/