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Export BLOB Contents Using UTL_FILE

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In a previous article I explained how to export the contents of a BLOB to a file using a Java stored procedure. In Oracle 9iR2 (9.2) it is also possible to perform this operation using new functionality provided by the UTL_FILE package.

First we create a directory object pointing to the destination directory.

CONN / AS SYSDBA

CREATE OR REPLACE DIRECTORY BLOBS AS '/tmp/';
GRANT READ, WRITE ON DIRECTORY BLOBS TO my_user;

Next we open the BLOB, read chunks into a buffer and write them to a file.

DECLARE
  l_file      UTL_FILE.FILE_TYPE;
  l_buffer    RAW(32767);
  l_amount    BINARY_INTEGER := 32767;
  l_pos       INTEGER := 1;
  l_blob      BLOB;
  l_blob_len  INTEGER;
BEGIN
  -- Get LOB locator
  SELECT col1
  INTO   l_blob
  FROM   tab1
  WHERE  rownum = 1;

  l_blob_len := DBMS_LOB.getlength(l_blob);
  
  -- Open the destination file.
  --l_file := UTL_FILE.fopen('BLOB_DIR','MyImage.gif','w', 32767);
  l_file := UTL_FILE.fopen('BLOB_DIR','MyImage.gif','wb', 32767);

  -- Read chunks of the BLOB and write them to the file
  -- until complete.
  WHILE l_pos <= l_blob_len LOOP
    DBMS_LOB.read(l_blob, l_amount, l_pos, l_buffer);
    UTL_FILE.put_raw(l_file, l_buffer, TRUE);
    l_pos := l_pos + l_amount;
  END LOOP;
  
  -- Close the file.
  UTL_FILE.fclose(l_file);
  
EXCEPTION
  WHEN OTHERS THEN
    -- Close the file if something goes wrong.
    IF UTL_FILE.is_open(l_file) THEN
      UTL_FILE.fclose(l_file);
    END IF;
    RAISE;
END;
/

Finally, you can check the file is produced correctly.

Port-specific Bug #2546782, raised against 9.2.0 on Windows 2000, reports wrong output from UTL_FILE.PUT_RAW.

Oracle 10g includes extra open modes (rb, wr, ab) to signify byte mode operation. The "wb" open mode can be used along with the PUT_RAW procedure to prevent extra newline characters being added on a Windows platform.

In reality you would probably put this code into a stored procedure, or packaged procedure. This example is available here.

CREATE OR REPLACE PROCEDURE blob_to_file (p_blob      IN  BLOB,
                                          p_dir       IN  VARCHAR2,
                                          p_filename  IN  VARCHAR2)
AS
  l_file      UTL_FILE.FILE_TYPE;
  l_buffer    RAW(32767);
  l_amount    BINARY_INTEGER := 32767;
  l_pos       INTEGER := 1;
  l_blob_len  INTEGER;
BEGIN
  l_blob_len := DBMS_LOB.getlength(p_blob);
  
  -- Open the destination file.
  l_file := UTL_FILE.fopen(p_dir, p_filename,'wb', 32767);

  -- Read chunks of the BLOB and write them to the file until complete.
  WHILE l_pos <= l_blob_len LOOP
    DBMS_LOB.read(p_blob, l_amount, l_pos, l_buffer);
    UTL_FILE.put_raw(l_file, l_buffer, TRUE);
    l_pos := l_pos + l_amount;
  END LOOP;
  
  -- Close the file.
  UTL_FILE.fclose(l_file);
  
EXCEPTION
  WHEN OTHERS THEN
    -- Close the file if something goes wrong.
    IF UTL_FILE.is_open(l_file) THEN
      UTL_FILE.fclose(l_file);
    END IF;
    RAISE;
END blob_to_file;
/

You might call this like the following.

DECLARE
  l_blob  BLOB;
BEGIN
  -- Get LOB locator
  SELECT col1
  INTO   l_blob
  FROM   tab1
  WHERE  rownum = 1;

  blob_to_file(p_blob     => l_blob,
               p_dir      => 'BLOB_DIR',
               p_filename => 'MyImage.gif');
END;
/

For more information see:

Hope this helps. Regards Tim...

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