博客

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

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;

import javax.servlet.http.HttpSession;

public class VerifyCodeServlet extends HttpServlet {

Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色

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);

}

public void service(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// 设置页面不缓存

response.setHeader(“Pragma”, “No-cache”);

response.setHeader(“Cache-Control”, “no-cache”);

response.setDateHeader(“Expires”, 0);

HttpSession session = request.getSession();

// 在内存中创建图象

int width = 55, height = 16;

BufferedImage image = new BufferedImage(width, height,

BufferedImage.TYPE_INT_RGB);// 获取图形上下文

Graphics g = image.getGraphics();// 生成随机类

Random random = new Random();// 设定背景色

g.setColor(getRandColor(200, 250));

g.fillRect(0, 0, width, height);// 设定字体

g.setFont(new Font(“Times New Roman”, Font.PLAIN, 18));// 画边框

// g.setColor(new Color());

// g.drawRect(0,0,width-1,height-1);

// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到

g.setColor(getRandColor(160, 200));

for (int i = 0; i < 155; 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);

}// 取随机产生的认证码(4位数字)

String sRand = “”;

for (int i = 0; i < 4; i++) {

String rand = String.valueOf(random.nextInt(10));

sRand += rand;

// 将认证码显示到图象中

g.setColor(new Color(20 + random.nextInt(110), 20 + random

.nextInt(110), 20 + random.nextInt(110)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成

g.drawString(rand, 13 * i + 3, 14);

}// 将认证码存入SESSION

session.setAttribute(“code”, sRand);

// 图象生效

g.dispose();// 输出图象到页面

ImageIO.write(image, “JPEG”, response.getOutputStream());

}

}