Oracle LOB

Penyedia Data .NET Framework untuk Oracle menyertakan kelas OracleLob, yang digunakan untuk bekerja dengan tipe data LOB.

OracleLob mungkin merupakan salah satu dari jenis data OracleType ini:

OracleLob berbeda dari OracleBFile dalam data yang disimpan di server, bukan dalam file fisik pada sistem operasi. Ini juga bisa menjadi objek baca-tulis, tidak seperti OracleBFile, yang selalu baca-saja.

Membuat, Mengambil, dan Menulis ke LOB

Contoh C# berikut menunjukkan bagaimana Anda dapat membuat LOB dalam tabel Oracle, lalu mengambil dan menulis ke LOB dalam bentuk objek OracleLob. Contoh menunjukkan menggunakan OracleDataReader objek dan metode Baca dan Tulis OracleLob. Contoh itu menggunakan jenis data Oracle BLOB, CLOB, dan NCLOB.

using System;  
using System.IO;
using System.Text;
using System.Data;
using System.Data.OracleClient;  
  
// LobExample  
public class LobExample  
{  
   public static int Main(string[] args)  
   {  
      //Create a connection.  
      OracleConnection conn = new OracleConnection(  
         "Data Source=Oracle8i;Integrated Security=yes");  
      using(conn)  
      {  
         //Open a connection.  
         conn.Open();  
         OracleCommand cmd = conn.CreateCommand();  
  
         //Create the table and schema.  
         CreateTable(cmd);  
  
         //Read example.  
         ReadLobExample(cmd);  
  
         //Write example  
         WriteLobExample(cmd);  
      }  
  
      return 1;  
   }  
  
   // ReadLobExample  
   public static void ReadLobExample(OracleCommand cmd)  
   {  
      int actual = 0;  
  
      // Table Schema:  
      // "CREATE TABLE tablewithlobs (a int, b BLOB, c CLOB, d NCLOB)";  
      // "INSERT INTO tablewithlobs values (1, 'AA', 'AAA', N'AAAA')";  
      // Select some data.  
      cmd.CommandText = "SELECT * FROM tablewithlobs";  
      OracleDataReader reader = cmd.ExecuteReader();  
      using(reader)  
      {  
         //Obtain the first row of data.  
         reader.Read();  
  
         //Obtain the LOBs (all 3 varieties).  
         OracleLob blob = reader.GetOracleLob(1);  
         OracleLob clob = reader.GetOracleLob(2);  
         OracleLob nclob = reader.GetOracleLob(3);  
  
         //Example - Reading binary data (in chunks).  
         byte[] buffer = new byte[100];  
         while((actual = blob.Read(buffer, 0, buffer.Length)) >0)  
            Console.WriteLine(blob.LobType + ".Read(" + buffer + ", " +
              buffer.Length + ") => " + actual);  
  
         // Example - Reading CLOB/NCLOB data (in chunks).  
         // Note: You can read character data as raw Unicode bytes
         // (using OracleLob.Read as in the above example).  
         // However, because the OracleLob object inherits directly
         // from the .NET stream object,
         // all the existing classes that manipulate streams can
         // also be used. For example, the
         // .NET StreamReader makes it easier to convert the raw bytes
         // into actual characters.  
         StreamReader streamreader =
           new StreamReader(clob, Encoding.Unicode);  
         char[] cbuffer = new char[100];  
         while((actual = streamreader.Read(cbuffer,
           0, cbuffer.Length)) >0)  
            Console.WriteLine(clob.LobType + ".Read(  
              " + new string(cbuffer, 0, actual) + ", " +
              cbuffer.Length + ") => " + actual);  
  
         // Example - Reading data (all at once).  
         // You could use StreamReader.ReadToEnd to obtain
         // all the string data, or simply  
         // call OracleLob.Value to obtain a contiguous allocation
         // of all the data.  
         Console.WriteLine(nclob.LobType + ".Value => " + nclob.Value);  
      }  
   }  
  
   // WriteLobExample  
   public static void WriteLobExample(OracleCommand cmd)  
   {  
      //Note: Updating LOB data requires a transaction.  
      cmd.Transaction = cmd.Connection.BeginTransaction();  
  
      // 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')";  
      cmd.CommandText = "SELECT * FROM tablewithlobs FOR UPDATE";  
      OracleDataReader reader = cmd.ExecuteReader();  
      using(reader)  
      {  
         // Obtain the first row of data.  
         reader.Read();  
  
         // Obtain a LOB.  
         OracleLob blob = reader.GetOracleLob(1/*0:based ordinal*/);  
  
         // Perform any desired operations on the LOB
         // (read, position, and so on).  
  
         // Example - Writing binary data (directly to the backend).  
         // To write, you can use any of the stream classes, or write  
         // raw binary data using
         // the OracleLob write method. Writing character vs. binary
         // is the same;  
         // however note that character is always in terms of
         // Unicode byte counts  
         // (for example, even number of bytes - 2 bytes for every  
         // Unicode character).  
         byte[] buffer = new byte[100];  
         buffer[0] = 0xCC;  
         buffer[1] = 0xDD;  
         blob.Write(buffer, 0, 2);  
         blob.Position = 0;  
         Console.WriteLine(blob.LobType + ".Write(  
           " + buffer + ", 0, 2) => " + blob.Value);  
  
         // Example - Obtaining a temp LOB and copying data
         // into it from another LOB.  
         OracleLob templob = CreateTempLob(cmd, blob.LobType);  
         long actual = blob.CopyTo(templob);  
         Console.WriteLine(blob.LobType + ".CopyTo(  
            " + templob.Value + ") => " + actual);  
  
         // Commit the transaction now that everything succeeded.  
         // Note: On error, Transaction.Dispose is called
         // (from the using statement)  
         // and will automatically roll back the pending transaction.  
         cmd.Transaction.Commit();  
      }  
   }  
  
   // CreateTempLob  
   public static OracleLob CreateTempLob(  
     OracleCommand cmd, OracleType lobtype)  
   {  
      //Oracle server syntax to obtain a temporary LOB.  
      cmd.CommandText = "DECLARE A " + lobtype + "; "+  
                     "BEGIN "+  
                        "DBMS_LOB.CREATETEMPORARY(A, FALSE); "+  
                        ":LOC := A; "+  
                     "END;";  
  
      //Bind the LOB as an output parameter.  
      OracleParameter p = cmd.Parameters.Add("LOC", lobtype);  
      p.Direction = ParameterDirection.Output;  
  
      //Execute (to receive the output temporary LOB).  
      cmd.ExecuteNonQuery();  
  
      //Return the temporary LOB.  
      return (OracleLob)p.Value;  
   }  
  
   // CreateTable  
   public static void CreateTable(OracleCommand cmd)  
   {  
      // Table Schema:  
      // "CREATE TABLE tablewithlobs (a int, b BLOB, c CLOB, d NCLOB)";  
      // "INSERT INTO tablewithlobs VALUES (1, 'AA', 'AAA', N'AAAA')";  
      try  
      {  
         cmd.CommandText   = "DROP TABLE tablewithlobs";  
         cmd.ExecuteNonQuery();  
      }  
      catch(Exception)  
      {  
      }  
  
      cmd.CommandText =
        "CREATE TABLE tablewithlobs (a int, b BLOB, c CLOB, d NCLOB)";  
      cmd.ExecuteNonQuery();  
      cmd.CommandText =
        "INSERT INTO tablewithlobs VALUES (1, 'AA', 'AAA', N'AAAA')";  
      cmd.ExecuteNonQuery();  
   }  
}  

Membuat LOB Sementara

Contoh C# berikut menunjukkan cara membuat LOB sementara.

OracleConnection conn = new OracleConnection(  
  "server=test8172; integrated security=yes;");  
conn.Open();  
  
OracleTransaction tx = conn.BeginTransaction();  
  
OracleCommand cmd = conn.CreateCommand();  
cmd.Transaction = tx;  
cmd.CommandText =
  "declare xx blob; begin dbms_lob.createtemporary(  
  xx, false, 0); :tempblob := xx; end;";  
cmd.Parameters.Add(new OracleParameter("tempblob",  
  OracleType.Blob)).Direction = ParameterDirection.Output;  
cmd.ExecuteNonQuery();  
OracleLob tempLob = (OracleLob)cmd.Parameters[0].Value;  
tempLob.BeginBatch(OracleLobOpenMode.ReadWrite);  
tempLob.Write(tempbuff,0,tempbuff.Length);  
tempLob.EndBatch();  
cmd.Parameters.Clear();  
cmd.CommandText = "myTable.myProc";  
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add(new OracleParameter(  
  "ImportDoc", OracleType.Blob)).Value = tempLob;  
cmd.ExecuteNonQuery();  
  
tx.Commit();  

Lihat juga

• Oracle dan ADO.NET
• Gambaran Umum ADO.NET