将Oracle 中的blob导出到文件中

declare
  l_directory varchar (200) := '__dir__' ;
    l_file UTL_FILE.FILE_TYPE;
    l_buffer RAW(32767);
    l_amount BINARY_INTEGER:=32767;
    l_pos NUMBER:=1;
    l_Blob Blob;
    l_Blob_len Number;
    l_lob_id number;
    CURSOR cur is
      select __id__ from __table_name__;
BEGIN
  open cur;
    loop
      fetch cur into l_lob_id;
      EXIT when cur%NOTFOUND;
      select __blob_fild__ into l_Blob from __table_name__ where __id__=l_lob_id ;
      l_file:=UTL_FILE.FOPEN(l_directory, 'adapter_blob.' ||to_char(l_lob_id)|| '.bin' , 'wb' ,32767);
      l_Blob_len:=dbms_lob.getlength(l_Blob);
      l_pos := 1;
      WHILE l_pos

        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;
      utl_file.fclose(l_file);
    end loop;
    exception
        when others then
        if utl_file.is_open(l_file) then
        utl_file.fclose(l_file);
        end if;
END ;