1. 序言
数据库应用程序,特别是基于WEB的数据库应用程序,常会涉及到图片信息的存储和显示。
通常我们使用的方法是将所要显示的图片存在特定的目录下,在数据库中保存相应的图片的名称,在JSP中建立相应的数据源,利用数据库访问技术处理图片信息。但是,如果我们想动态的显示图片,上述方法就不能满足需要了。我们必须把图片存入数据库,然后通过编程动态地显示我们需要的图片。实际操作中,可以利用JSP的编程模式来实现图片的数据库存储和显示。
2. 建立后台数据库
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[p]') and OBJECTPROPERTY(id, N'IsUserTable') = 1) drop table [dbo].[p] GO CREATE TABLE [dbo].[p] ( [picid] [int] IDENTITY (1, 1) NOT NULL , [picname] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL , [pic] [image] NULL ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] GO |
3.向数据库存储二进制图片
启动Dreamweaver MX后,新建一个JSP文件。其代码如下所示。
%@ page contentType="text/html;charset=gb2312"% % String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName() +":"+request.getServerPort()+path+"/"; % !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" html head base href="%=basePath%" titleMy JSP 'InputImage.jsp' starting page/title meta http-equiv="pragma" content="no-cache" meta http-equiv="cache-control" content="no-cache" meta http-equiv="expires" content="0" meta http-equiv="keywords" content="keyword1,keyword2,keyword3" meta http-equiv="description" content="This is my page" !-- link rel="stylesheet" type="text/css" href="styles.css" -- /head body form action="testimage.jsp" method="POST"br 题目input name="picname" type="text"br 图片input name="pic" type="file"br input type="Submit" name="button1" value="提交"br /form /body /html |
将此文件保存为InputImage.jsp文件,其中testimage.jsp文件是用来将图片数据存入数据库的,具体代码如下所示:
%@ page contentType="text/html;charset=gb2312"% %@ page import="java.sql.*" % %@ page import="java.util.*"% %@ page import="java.text.*"% %@ page import="java.io.*"% jsp:useBean id="conn" scope="page" class="dbconn.DBResult"/ % String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+ ":"+request.getServerPort()+path+"/"; % !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" html head base href="%=basePath%" titleMy JSP 'testimage.jsp' starting page/title meta http-equiv="pragma" content="no-cache" meta http-equiv="cache-control" content="no-cache" meta http-equiv="expires" content="0" meta http-equiv="keywords" content="keyword1,keyword2,keyword3" meta http-equiv="description" content="This is my page" !-- link rel="stylesheet" type="text/css" href="styles.css" -- /head body % request.setCharacterEncoding("gb2312"); //建立Statement对象 String picname=request.getParameter("picname"); String pic=request.getParameter("pic"); //获得所要显示图片的标题、存储路径、内容,并进行中文编码 FileInputStream str=new FileInputStream(pic); String sql="insert into p(picname,pic) values(?,?)"; PreparedStatement pstmt=conn.getPreparedStatement(sql); pstmt.setString(1,picname); pstmt.setBinaryStream(2,str,str.available()); pstmt.execute(); //将数据存入数据库 out.println("Success,You Have Insert an Image Successfully"); % /body /html |
4. 网页中动态显示图片
接下来我们要编程从数据库中取出图片,其代码如下所示。
%@ page contentType="text/html;charset=gb2312"% %@ page import="java.sql.*" % %@ page import="java.util.*"% %@ page import="java.text.*"% %@ page import="java.io.*"% jsp:useBean id="conn" scope="page" class="dbconn.DBResult"/ % String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+ ":"+request.getServerPort()+path+"/"; % !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" html head base href="%=basePath%" titleMy JSP 'testimageout.jsp' starting page/title meta http-equiv="pragma" content="no-cache" meta http-equiv="cache-control" content="no-cache" meta http-equiv="expires" content="0" meta http-equiv="keywords" content="keyword1,keyword2,keyword3" meta http-equiv="description" content="This is my page" !-- link rel="stylesheet" type="text/css" href="styles.css" -- /head body % int id= Integer.parseInt(request.getParameter("picid")); String sql = "select pic from p WHERE picid="+id; ResultSet rs=conn.getResult(sql); while(rs.next()) { ServletOutputStream sout = response.getOutputStream(); //图片输出的输出流 InputStream in = rs.getBinaryStream(1); byte b[] = new byte[0x7a120]; for(int i = in.read(b); i != -1;) { sout.write(b); //将缓冲区的输入输出到页面 in.read(b); } sout.flush(); //输入完毕,清除缓冲 sout.close(); } % /body /html |
将此文件保存为testimageout.jsp文件。下一步要做的工作就是使用HTML标记:
%@ page contentType="text/html;charset=gb2312"% %@ page import="java.sql.*" % %@ page import="java.util.*"% %@ page import="java.text.*"% %@ page import="java.io.*"% jsp:useBean id="conn" scope="page" class="dbconn.DBResult"/ % String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+ ":"+request.getServerPort()+path+"/"; % !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" html head base href="%=basePath%" titleMy JSP 'lookpic.jsp' starting page/title meta http-equiv="pragma" content="no-cache" meta http-equiv="cache-control" content="no-cache" meta http-equiv="expires" content="0" meta http-equiv="keywords" content="keyword1,keyword2,keyword3" meta http-equiv="description" content="This is my page" !-- link rel="stylesheet" type="text/css" href="styles.css" -- /head body % String sql = "select * from p"; ResultSet rs=conn.getResult(sql); while(rs.next()) { % ccid_file values="testimageout" % /" width="100" height="100" br % } rs.close(); % /body /html |