在Oracle 8i的SQL*Plus中如何利用LOB字段存取操作系统二进制文件

   在Oracle 8i的SQL*Plus中如何利用LOB字段存取操作系统二进制文件

                                                  
     广东省岭澳核电有限公司工程控制处管理信息科(518124)  黄福同
          

Oracle 8i数据库系统功能比前面版本更加完善，尤其是出现了BLOB,CLOB,NCLOB,
BFILE这些LOB(大型对象)类型来取代功能有限的LONG、LONGRAW类型。BLOB字段最
大长度为4G(4,294,967,295)字节,而且不再象LONGRAW那样每个表中只是限制有一
个字段是LONGRAW（最长2G）型的。BLOB,CLOB,NCLOB为内部BLOB(数据通常在数据
库中存放)，BFILE为外部LOB（所存储的只是指向外部操作系统文件的指针）,用户可
以使用PL/SQL的包DBMS_LOB来处理LOB数据，但是遗憾的是，DBMS_LOB包只能将二进
制操作系统文件写入到BLOB字段中，却无法将BLOB字段中的二进制操作系统文件取回
到操作系统中，估计将来会有所改善。本文将就如何在SQL*Plus将WORD文件存入取出
ORACLE中作详细解释说明，供各位同行参考。

实验的软件环境如下：Windows 2000 Advanced Server，Oracle 8.1.7，VC++6.0+SP5
硬件环境如下：双PIII866 CPU，768M内存

在internal这个用户下给scott用户授权如下：
SQL>grant create any directory to scott;
SQL>grant create any library to scott;
在scott这个用户下执行下述语句：

SQL>create table bfile_tab (bfile_column BFILE);
SQL>create table utl_lob_test (blob_column BLOB);
SQL>create or replace directory utllobdir as @#C:\DDS\EXTPROC@#;
SQL>set serveroutput on

然后执行下面语句就将C:\DDS\EXTPROC目录下的word文件COM.doc存入到utl_lob_test
表中的blob_column字段中了。

declare
   a_blob  BLOB;
   a_bfile BFILE := BFILENAME(@#UTLLOBDIR@#,@#COM.doc@#); --用来指向外部操作系统

文件
begin
   insert into bfile_tab values (a_bfile)
     returning bfile_column into a_bfile;
   insert into utl_lob_test values (empty_blob())
     returning blob_column into a_blob;
   dbms_lob.fileopen(a_bfile);
   dbms_lob.loadfromfile(a_blob, a_bfile, dbms_lob.getlength(a_bfile));
   dbms_lob.fileclose(a_bfile);
   commit;
end;
/
SQL>show errors
此时可以使用DBMS_LOB包的getlength这个procedure来检测是否已经将该word文件存入
到blob字段中了。如：
SQL> select dbms_lob.getlength(blob_column) from UTL_LOB_TEST;
结果如下：
DBMS_LOB.GETLENGTH(BLOB_COLUMN)
-------------------------------
                83968
说明该word文件已经存入到blob字段中去了。

下面将就如何取出该word文件到操作系统下作详细解释：
Oracle8.1.7只能用pro*c与OCI来实现该任务，所以Oracle服务器端必须支持pro*c
以及外部library，Oracle8.1.7数据库默认安装为支持pro*c以及外部Procedure，
用户可以自己检查一下listener.ora 和 tnsnames.ora这两个文件。
listener.ora中包含如下语句：
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = D:\oracle\ora81)
      (PROGRAM = extproc)
    )
    (SID_DESC =
      (GLOBAL_DBNAME = hft)
      (ORACLE_HOME = D:\oracle\ora81)
      (SID_NAME = hft)
    )
  )
tnsnames.ora中包含如下语句：
EXTPROC_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
    )
    (CONNECT_DATA =
      (SID = PLSExtProc)
      (PRESENTATION = RO)
    )
  )

下面这个文件为lob2file.c,具体作用是将BLOB中的二进制文件倒出到操作系统中。
/*begin of  lob2file.c*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <oci.h>
#include <ociextp.h>
#define  DEFAULT_CHUNK_SIZE  1024
static   int     logging;
static   char    logfile[512];
static   FILE   *logfilep = NULL;
int lob2file ( OCILobLocator     *a_lob,    /* the LOB */
               short              lbind,    /* LOB indicator */
               char              *path,     /* file to write */
               short              pind,     /* file indicator */
               int                plen,     /* filename length */
               char              *lpath,    /* logfile name */
               short              lpind,    /* logfile indicator */
               int                lplen,    /* logfile name length */
               int                logit,    /* logging enabled? */
               OCIExtProcContext *ctxt      /* OCI Context */
             )
{
   sword      errnum = 0;
   OCIEnv    *envhp = NULL;
   OCISvcCtx *svchp = NULL;
   OCIError  *errhp = NULL;
   char       lobfile[512];
   FILE      *lobfilep = NULL;
   /*
    * If required, open the log file for writing
    * Use the user provided logfile name if possible
    * Otherwise, default the logfile to lob2file.log
    */
   logging = logit;
   if (logging)
   {
      if (lpind == -1 || lplen == 0 || lplen >= 512)
      {
         strcpy(logfile, "lob2file.log");
      }
      else
      {
         strncpy(logfile, lpath, lplen);
         logfile[lplen] = @#\0@#;
      }
      logfilep = fopen(logfile, "w");
      if (logfilep == NULL)
      {
         if ((logfilep = fopen("lob2file.log", "w")) != NULL)
         {
            fprintf(logfilep, "Error: Unable to open logfile %s\n",

logfile);
            fprintf(logfilep, "Error: errno = %d\n", errno);
         }
      }
   }
   /*
    * Retrieve the environment, service context, and error handles
    */
   if ((errnum = OCIExtProcGetEnv(ctxt, &envhp,
                                  &svchp, &errhp)) != OCIEXTPROC_SUCCESS)
   {
      if (logging && logfilep != NULL)
      {
          fprintf(logfilep, "Error: Call to OCIExtProcGetEnv failed\n");
          fprintf(logfilep, "Error: OCIExtProcGetEnv returned %d\n",

errnum);
          fclose(logfilep);
          return -1;
      }
   }
   /*
    * Verify that the user has provided a name for the output file
    */
   if (pind == -1 || plen == 0)
   {
      char *errmsg = "Pathname is null or empty string";
      if (logging && logfilep != NULL)
      {
         fprintf(logfilep, "Error: %s\n", errmsg);
         fclose(logfilep);
      }
      errnum = 20001;
      OCIExtProcRaiseExcpWithMsg(ctxt, errnum, (text *)errmsg,

strlen(errmsg));
      return -1;
   }
   else /* Use the provided name */
   {
      strncpy(lobfile, path, plen);
      lobfile[plen] = @#\0@#;
   }
   /*
    * Verify that the user has provided a valid LOB locator
    */
   if (lbind == -1)
   {
      char *errmsg = "LOB locator is null";
      if (logging && logfilep != NULL)
      {
         fprintf(logfilep, "Error: %s\n", errmsg);
         fclose(logfilep);
      }
      errnum = 20002;
      OCIExtProcRaiseExcpWithMsg(ctxt, errnum, (text *)errmsg,

strlen(errmsg));
      return -1;
}
   if (logging && logfilep != NULL)
      fprintf(logfilep, "Opening OS file in write mode\n");
   /*
    * Open the output file for writing
    */
   if ((lobfilep = fopen(lobfile, "wb")) != NULL)
   {
      dvoid *chunk;
      ub4    cksz = 0, totsz = 0;
      if (logging && logfilep != NULL)
         fprintf(logfilep, "Getting total size for LOB\n");
      if (checkerr(ctxt, errhp,
                   OCILobGetLength(svchp, errhp, a_lob, &totsz)) != 0)
         return -1;
      /*
       * For 8.0.X the OCILogGetChunkSize will not have been called.
       * IN this case, reset the chunk size to 1K.
       */
      if (cksz == 0) cksz = DEFAULT_CHUNK_SIZE;
      if (logging && logfilep != NULL)
         fprintf(logfilep,
                  "Allocating %d bytes of memory for LOB chunks\n",
                   (int) cksz );
      /*
       * Dynamically allocate enough memory to hold a single chunk
       */
      if ((chunk = OCIExtProcAllocCallMemory(ctxt, (size_t) cksz)) != NULL)
      {
         int cnt = 1;
         ub4 amt = cksz, offset = 1;
         /*
          * Read data from the LOB and write it to the file while
          * more data remains.
          */
         while (offset < (int)totsz)
         {
            if (logging && logfilep != NULL)
               fprintf(logfilep,
                        "Reading chunk %d starting at %d for max %d

bytes\n",
                         cnt, (int) offset, (int) amt);
            errnum = OCILobRead(svchp, errhp, a_lob, &amt, offset,
                                chunk, cksz, (dvoid *) 0,
                                (sb4 (*)(dvoid *, dvoid *, ub4, ub1)) 0,
                                (ub2) 0, (ub1)SQLCS_IMPLICIT);
            if (checkerr(ctxt, errhp, errnum) != 0) return -1;
            if (logging && logfilep != NULL)
               fprintf(logfilep,
                        "Suclearcase/" target="_blank" >ccessfully read chunk containing %d bytes\n",
                         (int) amt);
            if (logging && logfilep != NULL)
               fprintf(logfilep,
                        "Writing %d bytes of chunk %d to file %s\n",
                         (int) amt, cnt, lobfile);
            if (fwrite((void *)chunk, (size_t)1, (size_t)amt, lobfilep) ==

amt)
            {
               if (logging && logfilep != NULL)
                  fprintf(logfilep, "Successfully wrote %d bytes to file

%s\n",
                          (int) amt, lobfile);
            }
            else
            {
               char *errmsg = "Write to OS file failed";
               if (logging && logfilep != NULL)
               {
                  fprintf(logfilep, "Error: %s\n", errmsg);
                  fprintf(logfilep, "Error: errno = %d\n", errno);
               }
               errnum = 20003;
               OCIExtProcRaiseExcpWithMsg(ctxt, errnum,
                                          (text *)errmsg, strlen(errmsg));
               return -1;
            }
            cnt++;
            offset += amt;
         }
         if (logfilep != NULL) fclose(logfilep);
         fclose(lobfilep);
         return 0;
      }
      else
      {
         if (logging && logfilep != NULL)
         {
            fprintf(logfilep, "Error: Unable to allocate memory\n");
            fclose(logfilep);
         }
         return -1;
      }
   }
   else
   {
      char *errmsg = "Unable to open file";
      if (logging && logfilep != NULL)
      {
         fprintf(logfilep, "Error: %s %s\n", errmsg, lobfile);
         fprintf(logfilep, "Error: errno = %d\n", errno);
         fclose(logfilep);
      }
      errnum = 20003;
      OCIExtProcRaiseExcpWithMsg(ctxt, errnum,
                                 (text *)errmsg, strlen(errmsg));
      return -1;
   }
}

int checkerr(OCIExtProcContext *ctxt, OCIError *errhp, sword status)
{
   sword errnum = 0;
   text errbuf[512];
   switch (status)
   {
     case OCI_SUCCESS_WITH_INFO:
        errnum = 20004;
        strcpy((char *)errbuf, "Error: OCI_SUCCESS_WITH_INFO");
        break;
     case OCI_NO_DATA:
        errnum = 20005;
        strcpy((char *)errbuf, "Error: OCI_NO_DATA");
        break;
     case OCI_NEED_DATA:
        errnum = 20006;
        strcpy((char *)errbuf, "Error: OCI_NEED_DATA");
        break;
     case OCI_INVALID_HANDLE:
        errnum = 20007;
        strcpy((char *)errbuf, "Error: OCI_INVALID_HANDLE");
        break;
     case OCI_STILL_EXECUTING:
        errnum = 20008;
        strcpy((char *)errbuf, "Error: OCI_STILL_EXECUTING");
        break;
     case OCI_CONTINUE:
        errnum = 20009;
        strcpy((char *)errbuf, "Error: OCI_CONTINUE");
        break;
     case OCI_ERROR:
        (void)OCIErrorGet((dvoid *) errhp, (ub4) 1, (text *) NULL,
                          (sb4 *) &errnum, (text *) errbuf,
                          (ub4) sizeof(errbuf), OCI_HTYPE_ERROR);
        break;
     default:
        break;
   }
   if (errnum != 0)
   {
      if (logging && logfilep != NULL)
      {
         fprintf(logfilep, "Error: %d %s\n", errnum, errbuf);
         fclose(logfilep);
      }
      (void)OCIExtProcRaiseExcpWithMsg(ctxt, errnum, errbuf,

strlen(errbuf));
   }
   return errnum;
}
/*end of file lob2file.c*/

将文件lob2file.c放到D:\oracle\ora81\plsql\demo目录下：然后在dos下执行下述编

译
语句将该文件编译成lob2file.dll文件，make.bat文件包含如下：

@echo off
cl -ID:\oracle\ora81\oci\include -D_DLL -D_MT /LD -Zi lob2file.c /link
D:\oracle\ora81\oci\lib\msvc\oci.lib msvcrt.lib  /nod:libcmt  /DLL 
/EXPORT:lob2file  /EXPORT:checkerr

进入D:\oracle\ora81\plsql\demo目录(DOS状态)执行make就可以将lob2file.c编
译成lob2file.dll文件了。

然后用scott连到sql*plus中，执行
SQL>CREATE OR REPLACE LIBRARY  UTLLOBLIB
     AS @#D:\oracle\ora81\plsql\demo\lob2file.dll@#
/
SQL>GRANT EXECUTE ON UTLLOBLIB TO PUBLIC

然后执行下述代码：
create or replace package utl_lob is
  procedure SetLogging(which BOOLEAN, a_log VARCHAR2);
  procedure UnloadToFile(a_lob BLOB, a_file VARCHAR2, status OUT NUMBER);
end utl_lob;
/
show errors
create or replace package body utl_lob is
  logSetting  BOOLEAN := FALSE;
  logFileName VARCHAR2(512) := NULL;
  procedure SetLogging(which BOOLEAN, a_log VARCHAR2) is
  begin
     logSetting := which;
     if (logSetting = TRUE) then
        logFileName := a_log;
     else
        logFileName := NULL;
     end if;
  end;

  function LobToFile(a_lob BLOB, a_file VARCHAR2,a_log VARCHAR2, logging

BOOLEAN)
  return BINARY_INTEGER   as external
  name "lob2file"
  library utlloblib
  LANGUAGE C
  with context
  parameters ( a_lob OCILOBLOCATOR,
               a_lob INDICATOR SHORT,
               a_file STRING,
               a_file INDICATOR SHORT,
               a_file LENGTH INT,
               a_log STRING,
               a_log INDICATOR SHORT,
               a_log LENGTH INT,
               logging INT,
               CONTEXT,
               RETURN );
  procedure UnloadToFile(a_lob BLOB, a_file VARCHAR2, status OUT NUMBER) is
  begin
     status := LobToFile(a_lob, a_file, logFileName, logSetting);
  end;
end utl_lob;
/
show errors
grant execute on utl_lob to public;

该代码创建package utl_lob，而utl_lob调用library utlloblib，我们的测试程序调

用
package utl_lob中的procedure SetLogging和UnloadToFile。在scott用户下执行如下
脚本，就可以将先前保存的COM.doc取出放到C:\DDS\EXTPROC\test.doc这个文件中，当

然
C:\DDS\EXTPROC这个目录必须存在。脚本执行完毕后生成两个文件test.log与test.doc

，
test.log纪录了取出的详细信息，test.doc是COM.doc的复制品，取出82K大小的文件大

约用了4秒。

--以下为测试脚本
set serveroutput on
declare
   a_blob BLOB;
   status NUMBER;
begin
   select blob_column into a_blob  from utl_lob_test;
   utl_lob.SetLogging(TRUE, @#C:\DDS\EXTPROC\test.log@#);
   utl_lob.UnloadToFile(a_blob, @#C:\DDS\EXTPROC\test.doc@#, status);
   dbms_output.put_line(@#Exit status = @# || status);
end;
/
大家对上面测试脚本稍微改动一下，形成一个带参数的Procedure供应用程序调用就可

以了。

 

原文转自：http://www.ltesting.net