随机生成验证码-蒲公英云

//login.jsp加入
<dt>验证码</dt>
                <dd>
                    <input type="text" name="code" size="8" maxlength="4" /> 
                    <img align="middle" src="VerifyCodeServlet" title="看不清，点击换一张"
                 onclick="this.src=this.src+'?'+<%=new Date().getTime()%>"/><span>${errorMsg}</span>
                </dd>

loginServlet添加

String loginCode=request.getParameter("code");
        UserService service=new UserService();
        boolean flagCode=service.isCodeEqual(loginCode, request);

service创建isCodeEqual方法

// 验证码验证
        public boolean isCodeEqual(String loginCode, HttpServletRequest request) {
            // TODO Auto-generated method stub
            boolean flag = false;
            // 获取session中的code
            String sessionCode = (String) request.getSession().getAttribute("code");
            System.out.println("session" + sessionCode);
            System.out.println("login" + loginCode);
            if (loginCode != null && sessionCode.equalsIgnoreCase(loginCode)) {
                flag = true;
            }
            return flag;
        }

随机四位验证码生成

package com.db.servlet;
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.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet("/VerifyCodeServlet")
public class VerifyCodeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public VerifyCodeServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("image/jpeg");
        // 设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // 在内存中创建图像
        int width = 90;
        int height = 35;
        BufferedImage image = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文
        Graphics g = image.getGraphics();
        // 随机类
        Random random = new Random();
        // 设定背景
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height);
        // 设定字体
        g.setFont(new Font("Times New Roman", Font.PLAIN, 30));
        // 随机产生干扰线
        g.setColor(getRandColor(160, 200));
        for (int i = 0; i < 100; 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);
        }
        // 随机产生4位验证码
        String[] codes = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
                "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", "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" };
        String code = "";
        for (int i = 0; i < 4; i++) {
            String str = codes[random.nextInt(codes.length)];
            code += str;
            // 将认证码显示到图象中
            g.setColor(new Color(50 + random.nextInt(110), 20 + random
                    .nextInt(110), 30 + 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(str, 18 * i + 13, 27); // 文字间距*i+距离左边距，上边距
        }
        HttpSession session = request.getSession();
        // 将认证码存入SESSION
        session.setAttribute("code", code);
        // 图象生效
        g.dispose();
        // 输出图象到页面
        ImageIO.write(image, "JPEG", response.getOutputStream());
        // 加上下面代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has
        // already been called ..........等异常
        response.getOutputStream().flush();
        response.getOutputStream().close();
        response.flushBuffer();
    }
    // 获取随机颜色
    private 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);
    }
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }
}