验证码

package com.yanzheng;


import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;


import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class ValidateCode 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 {
//禁止页面缓存
response.setHeader("Pragma", "NO=cache");
response.setHeader("Cache-Control", "No-cache");
response.setContentType("image/jpeg");//设置相应正文的MIME类型为图片
response.setDateHeader("EXpires", 0);
int width = 60,height=20;
/*
* 创建一个位于缓存中的图像
*/
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();//获取用于处理图形上下文的对象，相当于画笔
Random random = new Random();//创建生成随机数的对象
g.setColor(getRandomColor(200,250));//设置图像的背景颜色

g.fillRect(0, 0, width, height);//画一个矩形
g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
g.setColor(getRandomColor(160, 200));
for (int i = 0; i <130; 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);//在图像座标（x,y）和座标（x+xl,y+yl）之间画干扰线
}

String strCode="";
for (int i = 0; i <4; i++) {
String strNumber = String.valueOf(random.nextInt(10));
strCode = strCode+strNumber;
//设置字体的颜色
g.setColor(new Color(15+random.nextInt(120),15+random.nextInt(120),15+random.nextInt(120)));
g.drawString(strNumber, 13*i+6, 16);//将座标依次滑到图像上座标为（13*i+6, 16）
}
request.getSession().setAttribute("Code", strCode);//验证码保存到Session
g.dispose();//释放此图像的上下文以及它使用的系统资源
ImageIO.write(image, "JPEG", response.getOutputStream());//输出JPEG格式图像
response.getOutputStream().flush();
response.getOutputStream().close();
}


private Color getRandomColor(int i, int j) {
Random random = new Random();
Color randomColor = null;
if(i>255) i=255;
if(j>255) j=255;
//设置0-255之间的随机颜色
int r = i+random.nextInt(j-i);
int g = i+random.nextInt(j-i);
int b = i+random.nextInt(j-i);
randomColor = new Color(r,g,b);
return randomColor;
}

}

jsp页面<img src="ValidateCode" align="bottom" >