利用ORACLE JAVA存储过程实现BLOB图片导出

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  前几天有朋友让解决个问题:一个XX收单系统,需要的交易情况统计来自另外一套系统,以图片方式进行存储和导出查看.图

 

片以BLOB类型直接存在数据库中.本来以为就是个JAVA操作LOB的问题,但是因为是2次开发,所以必须遵循以前的规定,即所

 

有业务由存储过程实现.他们的选择是用DBMS_LOB和UTL_FILE包,导入图片到数据库没问题,但是在导出时始终不能正确

 

显示,发现导出后文件的大小与导入的图片不一致.

 

其实这又是9i的一个老问题了(为什么我又要说又呢),在Oracle DBA Tips Corner 中说明如下:

It should be noted that in Oracle9i this PL/SQL procedure does not work with all binary files. This is due to Oracle bug (BUG#: 2883782). The PL/SQL procedure that I use to write binary (raw) data out is UTL_FILE.PUT_RAW. This procedure, along with UTL_FILE.GET_RAW, was introduced in Oracle 9i Release 2 as previous versions of UTL_FILE only worked with TEXT files.

In Oracle9i there is currently a restriction of a maximum of 32k that can be written with PUT_RAW unless you insert new line characters in between the data. In Oracle10g there is a new binary mode. When files are opened with this mode, "wb", any amount of raw data can be written without the need for new lines. In short, this is a bug that can bite you if your binary files do not have a new line character within the RAW data in your MAX_LINESIZE buffer. If you do get bit by this bug in Oracle9i, there is no solution that I have found other than writing it in Java.

When I originally started writing and testing the procedure, I was using a fairly small image file (~ 1KB). This worked fine. I later tested a large PDF file (~ 3MB) and it failed (after writing only a small portion of the file) with the following exception:

BEGIN Write_BLOB_To_File; END;
*
ERROR at line 1:
ORA-29285: file write error
ORA-06512: at "SYS.UTL_FILE", line 18
ORA-06512: at "SYS.UTL_FILE", line 1007
ORA-06512: at "SCOTT.WRITE_BLOB_TO_FILE", line 74
ORA-06512: at line 1

Again, using the new binary write mode in Oracle10g when opening binary files should fix this.

 

大意如下:fopen如果用w模式打开，put_raw会自动加回车，哪怕只写一个字符,系统都会把换行符0A转换为0D0A,因为windows是以0D0A为换行符的,也就是说会自动加回车.而在10g中用wb模式打开,是以二进制方式打开,这种方式不会进行”回车符”和”换行符”的转换.也就是说,在9i中,读写2进制文件存在着问题....

 

  很可惜的是:

   1.不可能因为这1个功能就进行数据库地升级,9i也确实是一个BUG满天飞的版本......

   2.由于是2次开发,限制使用存储过程实现,因此无法使用纯JDBC或者spring的OracleLobHandler

 

  考虑了下,我的解决方案如下:

  1.利用一些外部工具,比如lobs_win32.exe(http://www.dbatools.net/software/lobs.zip)实现LOB操作,操作简单,但是不利于与当前项目集成,并且也有基于OCI方式的限制

  2.实际上PL/SQL对IO操作的支持并不好(9i还有个版本会因为参数utl_file_dir设置无效而导致pl/sql无法访问文件系统),而JAVA的IO操作则丰富得多.那么,我们为何不取长补短呢?也就是编写JAVA存储过程,利用简单易用的IO操作来代替PL/SQL中的程序包.

 

=====================我是分割线========================

 

  首先创建测试表,触发器以及对应的DIR:

CREATE TABLE IMAGE_LOB 
(I_ID NUMBER PRIMARY KEY NOT NULL,
I_IMG BLOB NOT NULL);

CREATE OR REPLACE TRIGGER tri_img
BEFORE INSERT ON fw.image_lob
FOR EACH ROW
BEGIN
  SELECT fw.se_test.NEXTVAL INTO :NEW.I_ID FROM dual;
END;

CREATE OR REPLACE DIRECTORY DIR_IMAGES AS 'C:\picture';

 

  接下来编写导入图片的过程:

CREATE OR REPLACE PROCEDURE P_IMG_INSERT (v_filename VARCHAR2)
IS
  v_bfile BFILE;--文件指针
  v_blob BLOB;
  DIR CONSTANT VARCHAR2(20) := 'DIR_IMAGES';--文件存放DIRECTORY
BEGIN
  /*通过empty_blob()函数将类型为blob的列初始化为空以便以后填充*/
  INSERT INTO fw.image_lob (I_IMG)
  VALUES (EMPTY_BLOB ()) RETURN I_IMG INTO v_blob;

  v_bfile:= BFILENAME (DIR, v_filename);--获得定位器指向的目录和文件
  IF (dbms_lob.fileexists(v_bfile)!=0) THEN --如果文件定位器指向的文件存在
    dbms_lob.fileopen(v_bfile,dbms_lob.file_readonly); --打开目标文件

    /*将文件字数据加载到指定的LOB类型变量*/
    dbms_lob.loadfromfile(v_blob,v_bfile,dbms_lob.getlength(v_bfile));

    dbms_lob.fileclose(v_bfile);--关闭文件
    COMMIT;
    dbms_output.put_line('已经从'||DIR||'目录中读取了图片'||v_filename||'向表中插入');

  ELSE--如果文件定位器指向的文件不存在
    dbms_output.put_line('文件没找到');
  END IF;
  EXCEPTION WHEN OTHERS THEN
  dbms_output.put_line(SQLERRM);
END;

 

  测试插入:

SQL> set serveroutput on
SQL> exec fw.p_img_insert(v_filename => '1.JPG');

已经从DIR_IMAGES目录中读取了图片1.JPG向表中插入

PL/SQL procedure successfully completed

 

  现在表格中数据如下:

SQL> select * from fw.image_lob;

      I_ID I_IMG
---------- -----
        21  
 
   
 
 
 
 
 
  接下来是重点,加载并编译AVA程序,很简单地IO操作:
 
 
CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "sp_exp_blob" AS
package util;

import java.io.FileOutputStream;
import java.io.OutputStream;

import oracle.sql.BLOB;

public class OracleBlobUtil {
	
		public static void exp(BLOB blob,String expDir) throws Exception{
		    byte[] bt = blob.getBytes(1, (int)blob.length());
		    OutputStream os = new FileOutputStream(expDir);
		    os.write(bt);
		    os.flush();
		    os.close();
	}
}
 
 
 
 
 
  创建对应的过程:
 
 
 
 
 
CREATE OR REPLACE PROCEDURE p_exp_blob(v_blob BLOB,v_exp_dir VARCHAR2)
AS LANGUAGE JAVA NAME 'util.OracleBlobUtil.exp(oracle.sql.BLOB,java.lang.String)';
 
 
 
 
 
  测试导出功能:
 
 
DECLARE
  v_blob fw.image_lob.i_img%TYPE;
BEGIN
  SELECT i_img INTO v_blob FROM fw.image_lob WHERE i_id=21;
  dbms_java.grant_permission( 'FW', 'SYS:java.io.FilePermission', 'c:/picture/1_exp.jpg', 'write' );
  fw.p_exp_blob(v_blob => v_blob,v_exp_dir => 'c:/picture/1_exp.jpg');
END;
 
 
 
 
 
   成功的话将在c:/picture下看到1_exp.jpg.
 
 
   注意兰色这行代码,是设置对文件的写的权限,如果没有的话,会出现java.security.AccessControlException: the Permission.....,可以参看老外的这篇帖子http://cn.forums.oracle.com/forums/thread.jspa?threadID=832298&tstart=0&messageID=3149561#3149561.更进一步的信息，可以查询Oracle的Java安全方面的文档.
 
 
  
 
 
  当然也可以单独地对用户进行权限授予
 
 
   
 
 
 
 
 
SQL> connect sys/is311027@feng as sysdba;
Connected to Oracle9i Enterprise Edition Release 9.2.0.1.0 
Connected as SYS

SQL> call dbms_java.grant_permission( 'FW', 'SYS:java.io.FilePermission', 'c:/picture/1_exp.jpg', 'write' );

Method called
 
 
 
 
 
 
 
 
  最后总结如下,利用从8i开始就引入的JVM,我们可以利用JAVA和PL/SQL进行互补.利用JAVA的各种优点来扩展数据库应用
 
 
 
 
 
的功能,并且充分利用高效的内存回收技术和线程管理方面的能力,而不再是局限于PL/SQL.而正如本文中的例子,PL/SQL和
 
 
 
 
 
Java 可以在同一个应用中和谐共处,2者是可以共存的.同时使用两个世界最好的方法，让我们能够开发出更好的数据库应
 
 
 
 
 
用.最后再说句,9i真龌龊....