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.io.OutputStream;
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;

@WebServlet(“check.do”)
public class CheckcodeServlet extends HttpServlet {
        //产生随即的字体
        private Font getFont() {
            Random random = new Random();
            Font font[] = new Font[5];
            font[0] = new Font("Ravie", Font.PLAIN, 24);
            font[1] = new Font("Antique Olive Compact", Font.PLAIN, 24);
            font[2] = new Font("Forte", Font.PLAIN, 24);
            font[3] = new Font("Wide Latin", Font.PLAIN, 24);
            font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, 24);
            return font[random.nextInt(5)];
        }

        protected void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            // 设置响应头 Content-type类型
            response.setContentType("image/jpeg");
            // 以下三句是用于设置页面不缓存
            response.setHeader("Pragma", "No-cache");
            response.setHeader("Cache-Control", "No-cache");
            response.setDateHeader("Expires", 0);

            OutputStream os = response.getOutputStream();
            int width = 83, height = 30;
            // 建立指定宽、高和BufferedImage对象
            BufferedImage image = new BufferedImage(width, height,
                    BufferedImage.TYPE_INT_ARGB);

            Graphics g = image.getGraphics(); // 该画笔画在image上
            Color c = g.getColor(); // 保存当前画笔的颜色，用完画笔后要回复现场
            g.fillRect(0, 0, width, height);//填充矩形背景
            

            char[] ch = "abcdefghjkmnpqrstuvwxyz23456789".toCharArray(); // 随机产生的字符串不包括 i l(小写L) o（小写O） 1（数字1）0(数字0)
            int length = ch.length; // 随机字符串的长度
            String sRand = ""; // 保存随机产生的字符串
            Random random = new Random();
            for (int i = 0; i < 4; i++) {
                // 设置字体
                g.setFont(getFont());
                // 随即生成0-9的数字
                String rand = new Character(ch[random.nextInt(length)]).toString();
                sRand += rand;
                // 设置随机颜色
                g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
                g.drawString(rand, 20 * i + 6, 25);
            }
            //产生随机干扰点
            for (int i = 0; i < 20; i++) {
                int x1 = random.nextInt(width);
                int y1 = random.nextInt(height);
                g.drawOval(x1, y1, 2,2);
            }
            g.setColor(c); // 将画笔的颜色再设置回去
            g.dispose();

            //将验证码记录到session
            request.getSession().setAttribute("safecode", sRand);
            //System.out.println(sRand);
            // 输出图像到页面
            ImageIO.write(image, "JPEG", os);

        }

        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }

}

页面实现

<imgalt="验证码"src="check.do"id="img1"/>
<ahref="javascript:void(0)"onclick="document.getElementById('img1').src='check.do?'+Math.random()" >看不清换一个</a>