| 标题 | 用JSP实现数据库图片的存储与显示实例 |
| 内容 | 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"/> <% 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"/> <% 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"/> <% 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> |
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