将图片从Oracle数据库中读出显示在JSP页面

最新推荐文章于 2022-04-13 11:31:46 发布

原创最新推荐文章于 2022-04-13 11:31:46 发布 · 749 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#jsp #oracle #数据库 #image #import #exception

Java Club 专栏收录该内容

1 篇文章

订阅专栏

本文介绍了一种将存储在数据库中的图片通过网页展示的方法，首先使用了PL/SQL过程实现，但由于安全性问题，最终采用Java Server Pages (JSP)来完成这一任务。文章详细介绍了JSP解决方案的实现步骤。

One of my recent assignments was to build a web page that needed to show images that are stored in a database.

CREATE TABLE PHOTOS
(
IMAGEID NUMBER(10),
IMAGE BLOB
)
/

CREATE OR REPLACE PROCEDURE Display_Image(p_id NUMBER) IS
    Photo BLOB
    v_amt NUMBER DEFAULT 4096;
    v_off NUMBER DEFAULT 1;
    v_raw RAW(4096);
BEGIN

    -- Get the blob image
    SELECT image
    INTO   Photo
    FROM   PHOTOS
    WHERE IMAGEID = p_id;

    owa_util.mime_header('images/gif');
    BEGIN
      LOOP
        -- Read the BLOB
        dbms_lob.READ(Photo, v_amt, v_off, v_raw);
        -- Display image
        htp.prn(utl_raw.cast_to_varchar2(v_raw));
        v_off := v_off + v_amt;
        v_amt := 4096;
      END LOOP;
      dbms_lob.CLOSE(Photo);
    EXCEPTION
      WHEN NO_DATA_FOUND THEN
        NULL;
    END;

END;
/

The web page could be called with the following URL and did what I was asked to do

img src="http://machine:port/pls/myapp/display_image?p_id=12" width="115" border="0"

This works like a charm but has a caveat that I discovered when presenting it to the network department. The network department didn’t like the idea of exposing the database server to the Internet, which indeed is considerably unsafe.

Back to the whiteboard, I thought of using Web Service. This approach just didn’t feel right and appeared to be too complex for this little solution to build. Eventually I decided to write a JavaServer Page to do the job.

The Java class to stream the image from the database column

package image;

import java.sql.*;
import java.io.*;
import java.util.*;
import oracle.jdbc.*;
import oracle.sql.*;

public class images
{
/*-------------------------
   *   Get the Blob image
   *------------------------*/
public static byte[] getPhoto (OracleConnection conn, int iNumPhoto)
       throws Exception, SQLException
{

    String req = "" ;
    Blob img ;
    byte[] imgData = null ;
    Statement stmt = conn.createStatement ();

    // Query
    req = "Select image From IMAGES Where ImageID = " + iNumPhoto ;

    ResultSet rset = stmt.executeQuery ( req );

    while (rset.next ())
    {
      img = rset.getBlob(1);
      imgData = img.getBytes(1,(int)img.length());
    }

    rset.close();
    stmt.close();

    return imgData ;

}

}

The JavaServer Page includes the bean so its methods can be accessed in the JSP page using scriplets and “photo” as a named bean reference

<%@ page import = "image.*" %>
<%@ page import = "java.io.*" %>
<%@ page import = "oracle.jdbc.OracleConnection" %>
<jsp:useBean id="photo" class="image.images" scope="session" />
<%

int iNumPhoto ;
oracle.jdbc.driver.OracleConnection conn = null;

if ( request.getParameter("imgID") != null )
{

    iNumPhoto = Integer.parseInt(request.getParameter("imgID")) ;

    try
    {
       conn = …………;
       conn.setAutoCommit (false);

       // get the image from the database
       byte[] imgData = photo.getPhoto( conn, iNumPhoto ) ;
       // display the image
       response.setContentType("image/gif");
       OutputStream o = response.getOutputStream();
       o.write(imgData);
       o.flush();
       o.close();
    }
    catch (Exception e)
    {
      e.printStackTrace();
      throw e;
    }
    finally
    {
      … Close the connexion … ;
    }
}
%>

To display the image on the web, I now use the following image URL

img src="image.jsp?imgID=12" width="115" border="0"