JSP實現基于WEB的數據庫圖片存儲與動態顯示
數據庫應用程序，特別是基于WEB的數據庫應用程序，常會涉及到圖片信息的存儲和顯示 。
通常我們使用的方法是將所要顯示的圖片存在特定的目錄下，在數據庫中保存相應的圖片 的名稱，在JSP中建立相應的數據源，利用數據庫訪問技術處理圖片信息。但是，如果我們想 動態的顯示圖片，上述方法就不能滿足需要了。我們必須把圖片存入數據庫，然后通過編程動 態地顯示我們需要的圖片。實際操作中，可以利用JSP的編程模式來實現圖片的數據庫存儲和 顯示。
建立后臺數據庫
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向數據庫存儲二進制圖片
啟動Dreamweaver MX后，新建一個JSP文件。其代碼如下所示。
<%@ 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"> 題目<input name="picname" type="text"> 圖片<input name="pic" type="file"> <input type="Submit" name="button1" value="提交"> </form> </body></html>
將此文件保存為InputImage.jsp文件，其中testimage.jsp文件是用來將圖片數據存入數據 庫的，具體代碼如下所示：
<%@ 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對象String picname=request.getParameter("picname");String pic=request.getParameter("pic");//獲得所要顯示圖片的標題、存儲路徑、內容，并進行中 文編碼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();//將數據存入數據庫out.println("Success,You Have Insert an Image Successfully");%></body></html>
網頁中動態顯示圖片
接下來我們要編程從數據庫中取出圖片，其代碼如下所示。
<%@ 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(); // 圖片輸出的輸出流 InputStream in = rs.getBinaryStream(1); byte b[] = new byte[0x7a120]; for(int i = in.read(b); i != -1;) { sout.write(b); //將緩沖區的輸入 輸出到頁面 in.read(b); } sout.flush (); //輸入完畢，清除緩沖 sout.close(); } %> </body></html>
將此文件保存為testimageout.jsp文件。下一步要做的工作就是使用HTML標記：
<%@ 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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