用JSP实现数据库图片的存储与显示实例
1. 引言
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%>">
<title>My 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%>">
<title>My 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%>">
<title>My 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%>">
<title>My 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>