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JSP实现基于WEB的数据库图片存储与动态显示

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。

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

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">题目<input name="picname" type="text">图片<input name="pic" type="file"> <input type="Submit" name="button1" value="提交">  </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>

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"> <% } rs.close(); %></body></html>

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