用ServletJSP动态生成英文、数字图像验证码

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Date;

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 {

// Process the HTTP Get request

public void doGet(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);

// 设置图片的长宽

int width = 62, height = 22;

// ////// 创建内存图像

BufferedImage image = new BufferedImage(width, height,

BufferedImage.TYPE_INT_RGB);

// 获取图形上下文

Graphics g = image.createGraphics();

// 设定图像背景色(因为是做背景，所以偏淡)

g.setColor(getRandColor(180, 250));

g.fillRect(0, 0, width, height);

// 设置字体

g.setFont(new Font("Times New Roman", Font.PLAIN, 17));

// /////设置默认生成4个验证码

int length = 4;

java.util.Random rand = new Random(); // 设置随机种子

/*

* if (request.getParameter("length") != null) { try { length =

* Integer.parseInt(request.getParameter("length")); }catch

* (NumberFormatException e) {} }

*/

// 设置备选验证码:包括"a-z"和数字"0-9"

String base = "abcdefghijklmnopqrstuvwxyz0123456789";

int size = base.length();

StringBuffer str = new StringBuffer();

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

int start = rand.nextInt(size);

String tmpStr = base.substring(start, start + 1);

str.append(tmpStr);

// 生成随机颜色(因为是做前景，所以偏深)

g.setColor(getRandColor(10, 150));

// 将此字画到图片上

// g.drawString(str.toString(), 4, 17);

g.drawString(tmpStr, 13 * i + 6 + rand.nextInt(5), 14 + rand

.nextInt(6));

}

// 将认证码存入session

request.getSession().setAttribute("valiCode", str.toString());

// 图象生效

g.dispose();

// 输出图象到页面

ImageIO.write(image, "JPEG", response.getOutputStream());

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

this.doGet(request, response);

}

// 给定范围获得一个随机颜色

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);

}

}