jsp 验证码图片显示不了
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%
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>登录界面</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">
-->
<script type="text/javascript">
function refreshCc() //刷新图片
{
var ccImg = document.getElementById("checkCodeImg");
nowTime = new Date();
ccImg.src= "CheckCodeServlet?e=" + nowTime.getTime();
}
function aa()
{
document.all.check_code.value="";
}
function check()
{
if(!isEmpty(f1.user,"用户名或邮箱") || !isEmpty(f1.pass,"密码")
|| !isEmpty(f1.check_code, "验证码"))
{
return false;
}
return true;
}
function isEmpty(obj,msg)
{
if(obj.value.length==0)
{
alert('请输入'+msg+'！ ');
return false;
}
return true;
}
</script>
</head>
<body>
<form action="LoginSerlet" method="post">
用户：<input type="text" name="username" /> <br /> 密码：<input
type="password" name="password" /><br />
验证码： <input name="check_code"
type="text" onClick="aa()" maxlength="4" class="login-input">
<br> <img
src="<%=path%>CheckCodeServlet" width="80" height="25"
align="bottom" id="checkCodeImg"> <a
href="javascript:refreshCc();" target="_self" class="style8">换一张
</a><br> <input type="submit" value="登录" /> <input type="reset" value="重置" />
</form>
</body>
</html>
package com.servlet;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import
import
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class CheckCodeServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
private static int WIDTH = 80;
private static int HEIGHT = 25;
@Override
protected void service(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
HttpSession session = request.getSession();
response.setContentType("images/jpg");
ServletOutputStream sos = response.getOutputStream();
// 设置浏览器不要缓存数据
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
// 创建内存图象并获得其图形上下文
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
// 产生随机的认证码
char[] rands = this.generateCheckCode();
// 产生图像
this.drawBackground(g);
this.drawRands(g, rands);
// 结束图像的绘制过程，完成图像
g.dispose();
// 将图像输出到客户端
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ImageIO.write(image, "JPEG", bos);
byte[] buf = bos.toByteArray();
response.setContentLength(buf.length);
// 下面的语句也可写成：bos.writeTo(sos);
sos.write(buf);
bos.close();
sos.close();
// 将当前验证码存入到Session中
session.setAttribute("check_code", new String(rands));
// 直接使用下面的代码将有问题，Session对象必须在提交响应前获得
// request.getSession().setAttribute("check_code",new String(rands));
}
// 定义验证码的字符表
public char[] generateCheckCode() {
String chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
char[] rands = new char[4];
for (int i = 0; i < 4; i++) {
int rand = (int) (Math.random() * 62);
rands[i] = chars.charAt(rand);
}
return rands;
}
// 在不同的高度上输出验证码的每个字符
public void drawRands(Graphics g, char[] rands) {
g.setColor(Color.BLACK);
g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 22));
g.drawString("" + rands[0], 5, 22);
g.drawString("" + rands[1], 24, 17);
g.drawString("" + rands[2], 39, 24);
g.drawString("" + rands[3], 56, 18);
System.out.println(rands);
}
// 画背景并随机产生120个干扰点
public void drawBackground(Graphics g) {
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, WIDTH, HEIGHT);
for (int i = 0; i < 120; i++) {
int x = (int) (Math.random() * WIDTH);
int y = (int) (Math.random() * HEIGHT);
int red = (int) (Math.random() * 255);
int green = (int) (Math.random() * 255);
int blue = (int) (Math.random() * 255);
g.setColor(new Color(red, green, blue));
g.drawOval(x, y, 1, 0);
}
}
}
