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最后更新时间：2008-08-26
编写一个Servlet import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
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 int WIDTH = 60;
private static int HEIGHT = 20;
public char[] generateCheckCode() {
// 定义验证码的字符表
String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char[] rands = new char[4];
for (int i = 0; i < 4; i++) {
int rand = (int) (Math.random() * 36);
rands[i] = chars.charAt(rand);
}
return rands;
}
public void drawRands(Graphics g, char[] rands) {
g.setColor(Color.BLACK);
g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 18));
// 在不同的高度上输出验证码的每个字符
g.drawString("" + rands[0], 1, 17);
g.drawString("" + rands[1], 16, 15);
g.drawString("" + rands[2], 31, 18);
g.drawString("" + rands[3], 46, 16);
}
public void drawBackground(Graphics g) {
// 画背景
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, WIDTH, HEIGHT);
// 随机产生120个干扰点
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);
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
response.setContentType("image/jpeg");
ServletOutputStream sos = response.getOutputStream();
// 设置浏览器不缓存此图片
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
// 创建内存图像并获得其图形上下文
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
// 产生随机的验证码
char[] rands = generateCheckCode();
// 产生图像
drawBackground(g);
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);
sos.write(buf);
bos.close();
sos.close();
// 将当前验证码存入到session中
session.setAttribute("checkCode", new String(rands));
System.out.println(session.getAttribute("checkCode"));
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
编写一个html页面 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>test.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
<script type="text/javascript">
function ajaxMethod(cid){
document.getElementById(cid).setAttribute("src",null);
//加上随机数的目的是为了每次都改变url 让浏览器不要加载缓存
var svalue = "/JsParserXML/servlet/CheckCodeServlet?id=" + Math.random();
document.getElementById(cid).setAttribute("src",svalue);
}
function colorblue(id){
document.getElementById(id).color="blue";
}
function colorblack(id){
document.getElementById(id).color="black";
}
</script>
</head>
<body>
<font size="2">验证码 :</font>
<img id="checkCodeImage" src="/JsParserXML/servlet/CheckCodeServlet" style="cursor:pointer" onclick="javascript:ajaxMethod('checkCodeImage');"/>
<a style="cursor:pointer" onclick="javascript:ajaxMethod('checkCodeImage');"><font id="fontId" size="2"><u onmouseover="colorblue('fontId');" onmouseout="colorblack('fontId');">看不清换一个</u></font></a>
</body>
</html>
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