1.生成验证码的servlet
package com.nanjing.zzu.ssp.common;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
public class RandomCodeServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Random random = new Random();
int width = 70, height = 25;
// 创建BufferedImage对象，设置图片的长度宽度和色彩。
BufferedImage image = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
OutputStream os = response.getOutputStream();
// 取得Graphics对象，用来绘制图片
Graphics g = image.getGraphics();
// 绘制图片背景和文字,释放Graphics对象所占用的资源。
g.setColor(getRandColor(200, 250));
// 设置内容生成的位置
g.fillRect(0, 0, width, height);
// 设置内容的字体和大小
g.setFont(new Font("Times New Roman", Font.PLAIN, 25));
// 设置内容的颜色：主要为生成图片背景的线条
g.setColor(getRandColor(160, 200));
// 画边框。
g.setColor(Color.BLACK);
g.drawRect(0, 0, width - 1, height - 1);
// 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。
g.setColor(Color.BLACK);
// 图片背景上随机生成155条线条，避免通过图片识别破解验证码
for (int i = 0; i < 30; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x, y, x + xl, y + yl);
}
// 生成四位的随机数,生成一个数，写一个
String[] s = {"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K",
"L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W",
"X", "Y", "Z","1","2","3","4","5","6","7","8","9","0"};
String content = "";
for (int i = 0; i < 4; i++) {
String rand = "";
if (random.nextBoolean()) {
rand = String.valueOf(random.nextInt(10));
} else {
int index = random.nextInt(35);
rand = s[index];
}
content += rand;
g.setColor(new Color(20 + random.nextInt(10), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
g.drawString(rand, 13 * i + 6, 20);
}
// 释放此图形的上下文以及它使用的所有系统资源，类似于关闭流
g.dispose();
// 将生成的验证码值(即运算结果的值)放到session中，以便于后台做验证。
HttpSession session = request.getSession();
session.setAttribute("result", content);
// 通过ImageIO对象的write静态方法将图片输出。
ImageIO.write(image, "JPEG", os);
os.close();
}
/**
* 生成随机颜色
*
* @param fc
* @param bc
* @return
*/
public Color getRandColor(int fc, int bc) {
Random random = new Random();
if (fc > 255)
fc = 255;
if (bc > 255)
bc = 255;
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
}
2.配置xml
<servlet>
<servlet-name>RandomCode</servlet-name>
<servlet-class>com.nanjing.zzu.ssp.common.RandomCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RandomCode</servlet-name>
<url-pattern>*.RandomCode</url-pattern>
</servlet-mapping>
3.登陆页面
<script type="text/javascript">
function changeImg()
{ document.getElementById("validatecodeimg").src=Math.round(Math.random()*10000)+".RandomCode ";
}
</script>
<body>
<div align="center">
<img id="validatecodeimg" alt="看不清？点击刷新" onclick="javascript:changeImg()" src="first.RandomCode " align="top" />
<a href="javascript:changeImg()">看不清？点击刷新</a>
</div>
</body>
</html>