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> |