读取并显示已写入ORACLE数据库中的图片

来源：互联网发布：授权系统源码搭建编辑：程序博客网时间：2024/04/28 13:42

上篇文章我们已经完成了图片文件上传到数据库，现在我们需要将图片文件读出并显示到网页中指定的位置。

一、新建一个JSP用于显示图片。名称了displayImg.jsp

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%@ page import="voucher.basic.readImg" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%
response.setContentType("image/jpeg");

byte[] data = null;

String strid = request.getParameter("zpid");
          //String strid = "8";
          readImg reimg = new readImg();
          data = reimg.getImgdata(strid);


              //获取图片的byte数据
              //data = QueryPhoto.GetImgByteById(strid);

              ServletOutputStream outputStream = response.getOutputStream();

              outputStream.write(data, 0, data.length);
              outputStream.close();
              outputStream = null;
              response.flushBuffer();
              //清除输出流，防止释放时被捕获异常
              out.clear();
              out = pageContext.pushBody();

      %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'delUser.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">

</head>

<body></body>
</html>

二、新建一个类，用于读取指定的图片

package voucher.basic;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class readImg {

public byte[] getImgdata(String imgId){
  byte[] data = null;
  DBHelper dbc = new DBHelper();
  Connection dbcon = dbc.openDataBase();
  try {
   Statement stat = dbcon.createStatement();
   String mySql = "select IMG from TESTIMG where IMGID = '" + imgId + "'";
   ResultSet rs = stat.executeQuery(mySql);
   if(rs.next()){
    java.sql.Blob blob = rs.getBlob("IMG");
    InputStream inStream = blob.getBinaryStream();
    int nSize = (int)blob.length();
    data = new byte[nSize];
    try {
     inStream.read(data);
     inStream.close();
    } catch (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }

  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  return data;

}

}

三、在网页中需要显示图片的位置插入图像占位符，使其SRC指向displayImg.jsp?imgId=图片ID。见下例

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%@ page import="voucher.basic.DBHelper" %>
<%@ page import="java.sql.*" %>
<%@ page import="java.io.InputStream" %>

<%
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 'readimg.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">

</head>

<body>
<img name="img" src="displayimg.jsp?imgId=9" width="687" height="366"> //这里的imgId可以使用<%=imgId%>完成变化
</body>
</html>

需要说明的是，这里给出的最后一个应用网页，只是静态地显示了一幅图片，如果需要根据选择显示图片，可以在选择图片ID的select控件的处加onclick="selectImg(this)"，同时在网页中加入以下javascript

function selectImg(obj){

document.getElementById("img").src = "displayImg.jsp?imgId=" + obj.value;

}