以下是我的两种实现方式：
方式一：
该方式进行的操作是，将一大于4Kb的txt文件写入Clob对象或者从该Clob字段读取出来并创建一个txt文件来保存。这些操作通过分段读取来实现。
public void SaveMassiveData()
{
// Declare Oracle objects
OracleConnection connection = new OracleConnection(ConnStr);
OracleCommand cmd = new OracleCommand("", connection);
OracleTransaction transaction;
OracleDataReader reader;
OracleClob clob;
try
{
connection.Open();
Console.WriteLine("Connected to database.../n");
// Start a transaction
transaction = connection.BeginTransaction();
// Lock the result set using the "FOR UPDATE" clause
cmd.CommandText = "SELECT " + Clobcol + " FROM " + Table + " FOR UPDATE";
reader = cmd.ExecuteReader();
reader.Read();
clob = reader.GetOracleClob(0);
clob.Erase();
string content = string.Empty;
using (StreamReader sr = new StreamReader(srcPath))
{
content = sr.ReadToEnd();
}
char[] buffer = new char[BufferLength];
// Save the content into memory
using (MemoryStream ms = new MemoryStream(Encoding.GetEncoding("UTF-8").GetBytes(content)))
{
int readCounts = 0;
using (StreamReader sr = new StreamReader(ms))
{
while (sr.Peek() > -1)
{
readCounts = sr.Read(buffer, 0, BufferLength);
clob.Write(buffer, 0, readCounts);
}
clob.Flush();
}
}
Console.WriteLine("Save Massive data Succeeded!");
// Commit transaction
transaction.Commit();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
cmd.Dispose();
connection.Close();
connection.Dispose();
}
}
public void FetchMassiveData()
{
// Declare Oracle objects
OracleConnection connection = new OracleConnection(ConnStr);
OracleCommand cmd = new OracleCommand("", connection);
OracleTransaction transaction;
OracleDataReader reader;
OracleClob clob;
try
{
connection.Open();
Console.WriteLine("Connected to database.../n");
// Start a transaction
transaction = connection.BeginTransaction();
cmd.CommandText = "SELECT " + Clobcol + " FROM " + Table;
reader = cmd.ExecuteReader();
reader.Read();
clob = reader.GetOracleClob(0);
int readCounts;
char[] buffer = new char[BufferLength];
using (FileStream fs = new FileStream(desPath, FileMode.Create))
{
StreamWriter sw = new StreamWriter(fs);
while ((readCounts = clob.Read(buffer, 0, BufferLength)) > 0)
{
sw.Write(buffer, 0, readCounts);
}
sw.Flush();
sw.Close();
}
Console.WriteLine("Fetch Massive data Succeeded!");
// Commit transaction
transaction.Commit();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
cmd.Dispose();
connection.Close();
connection.Dispose();
}
}
方式二：
事实上Oracle官方提供的ODAC112011beta插件中的Oracle.DataAccess命名空间已经提供了类似于ADO.NET的相关接口，因此针对Oracle中各种类型字段的操作可以使用这些方法直接实现，而无需考虑字段大小的问题。
方式二实现的操作是从Oracle数据库中读取Clob大字段(大于4Kb)并返回一个DataTable，及将大于4Kb的txt文件存入Oracle数据库中的Clob字段。
public DataTable FetchDBClobFiled(string sql)
{
if ((sql == null) || (sql.Length == 0))
{
return null;
}
OracleTransaction transaction;
DataTable dt = new DataTable();
try
{
conn.Open();
// Start a transaction
transaction = conn.BeginTransaction();
adapter.Fill(dt);
// Commit transaction
transaction.Commit();
return dt;
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
return null;
}
finally
{
adapter.Dispose();
cmd.Dispose();
conn.Close();
conn.Dispose();
}
}
以上代码省略了connection，adapter及command的定义，其中传入的查询语句为简单的Select语句如“"SELECT ID, CLOBCOL, CLOBCOL2, CLOBCOL3, CLOBCOL4 FROM TableName"”。
public void UpdateDBWithClobField(string sql)
{
if ((sql == null) || (sql.Length == 0))
{
return;
}
OracleTransaction transaction;
OracleParameter[] clobParams = new OracleParameter[4];
try
{
conn.Open();
// Start a transaction
transaction = conn.BeginTransaction();
string content = string.Empty;
using (StreamReader sr = new StreamReader(srcPath))
{
content = sr.ReadToEnd();
}
clobParams[0] = cmd.Parameters.Add("CLOBCOL", OracleDbType.Clob, content, ParameterDirection.Input);
clobParams[1] = cmd.Parameters.Add("CLOBCOL2", OracleDbType.Clob, content,ParameterDirection.Input);
clobParams[2] = cmd.Parameters.Add("CLOBCOL3", OracleDbType.Clob, content,ParameterDirection.Input);
clobParams[3] = cmd.Parameters.Add("CLOBCOL4", OracleDbType.Clob, content,ParameterDirection.Input);
cmd.ExecuteNonQuery();
// Commit transaction
transaction.Commit();
