C# 读写 Oracle BLOB 数据

using System;


using System.Data.OracleClient;


using System.IO;




namespace fenghua.Data.Oracle


{


/// <summary>


/// Class1 的摘要说明。


/// </summary>


public class OracleLobData


{


private OracleConnection conn;


public OracleLobData()


{


//


// TODO: 在此处添加构造函数逻辑


//


}




/*


* 在调用此函数之前需要写插入一个字符串到 BLOB 中比如：


* Select some data.


* Table Schema:


* "CREATE TABLE tablewithlobs (a int, b BLOB, c CLOB, d NCLOB)";


* "INSERT INTO tablewithlobs values (1, 'AA', 'AAA', N'AAAA')";


* 否则程序会在 OracleLob tempLob = reader.GetOracleLob(0) 处出错。


*/


/// <summary>


/// 文件写入到 Oracle Blob 字段中。


/// </summary>


/// <param name="idData">id 值</param>


/// <param name="fileName">文件名</param>


/// <param name="id">id 键</param>


/// <param name="blob">blob 键</param>


/// <param name="tableName">表名</param>


public void WriteBlob(int idData, string fileName, string id, string blob, string tableName)


{


string connString = "server=oratest;User ID=kttest;Password=test";


using(conn = new OracleConnection(connString))


{


try


{


conn.Open();


OracleCommand cmd = conn.CreateCommand();




// 利用事务处理（必须）


OracleTransaction transaction = cmd.Connection.BeginTransaction();


cmd.Transaction = transaction;




// 获得 OracleLob 指针


cmd.CommandText = "select " + blob + " from " + tableName + " where " + id + " = " + idData + " FOR UPDATE";


OracleDataReader reader = cmd.ExecuteReader();


using(reader)


{


//Obtain the first row of data.


reader.Read();


//Obtain a LOB.


OracleLob tempLob = reader.GetOracleLob(0);




// 将文件写入 BLOB 中


FileStream fs = new FileStream(fileName,FileMode.Open);


tempLob.BeginBatch(OracleLobOpenMode.ReadWrite);


int length = 10485760;


byte[] Buffer = new byte[length];


int i;


while((i = fs.Read(Buffer,0,length)) > 0)


{


tempLob.Write(Buffer,0,i);


}


fs.Close();


tempLob.EndBatch();


cmd.Parameters.Clear();


}


// 提交事务


transaction.Commit();


}


catch(Exception ex)


{


throw ex;


}


finally


{


conn.Close();


}


}


}




/// <summary>


/// 读取 Oracle Blob 到文件中。


/// </summary>


/// <param name="idData">id 值</param>


/// <param name="fileName">文件名</param>


/// <param name="id">id 键</param>


/// <param name="blob">blob 键</param>


/// <param name="tableName">表名</param>


public void ReadBlob(int idData,string fileName, string id, string blob, string tableName)


{


string connString = "server=oratest;User ID=kttest;Password=test";


using(conn = new OracleConnection(connString))


{


try


{


conn.Open();


OracleCommand cmd = conn.CreateCommand();




// 利用事务处理（必须）


OracleTransaction transaction = cmd.Connection.BeginTransaction();


cmd.Transaction = transaction;




// 获得 OracleLob 指针


string sql = "select " + blob + " from " + tableName + " where " + id + " = " + idData;


cmd.CommandText = sql;


OracleDataReader dr = cmd.ExecuteReader();


dr.Read();


OracleLob tempLob = dr.GetOracleLob(0);


dr.Close();




// 读取 BLOB 中数据，写入到文件中


FileStream fs = new FileStream(fileName,FileMode.Create);


int length = 1048576;


byte[] Buffer = new byte[length];


int i;


while((i = tempLob.Read(Buffer,0,length)) > 0)


{


fs.Write(Buffer,0,i);


}


fs.Close();


tempLob.Clone();


cmd.Parameters.Clear();




// 提交事务


transaction.Commit();


}


catch(Exception ex)


{


throw ex;


}


finally


{


conn.Close();


}


}


}


}


}