验证码生成和验证servlet

/**    * 随机生成验证码 * @author vinyu   * @version 1.0 * @Create Date:2015年2月9日 下午1:06:48    */    package servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;import java.util.Random;import javax.imageio.ImageIO;import javax.security.auth.message.callback.PrivateKeyCallback.Request;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class CAPTCHAServlet extends HttpServlet {//验证码图片的宽度。    private int width=80;    //验证码图片的高度。    private int height=25;public void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {String action = req.getParameter("action");if("check".equals(action)){//验证验证码checkCode(req, resp);}else{//生成验证码getCode(req, resp);}}//验证验证码public void checkCode(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {String ucode = req.getParameter("code");//用户传过来的验证码//系统生成的验证码String scode = req.getSession().getAttribute("CAPTCHA").toString();PrintWriter out = resp.getWriter();if(scode.equalsIgnoreCase(ucode)){out.print("true");}else{out.print("false");}out.flush();out.close();}    //生成验证码public void getCode(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//内存图片    BufferedImage buffImg=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);        //得到画笔         Graphics2D g=buffImg.createGraphics();                //创建一个随机数生成器类。        Random random=new Random();                //给画笔设置颜色        g.setColor(Color.WHITE);        //填充一个矩形        g.fillRect(0,0,width,height);                //创建字体，字体的大小应该根据图片的高度来定。        Font font=new Font("Times New Roman",Font.PLAIN,22);        //设置字体。        g.setFont(font);                //设置画笔为黑色        g.setColor(Color.BLACK);        //画边框         g.drawRect(0,0,width-1,height-1);                //随机产生160条白干扰线，使图象中的认证码不易被其它程序探测到。        g.setColor(Color.WHITE);        for (int i=0;i<160;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);        }                        //randomCode用于保存随机产生的验证码，以便用户登录后进行验证。        StringBuffer captcha =new StringBuffer();        int red=0,green=0,blue=0;        char[] ch = {'a','b','c','d','e','f','g','h','i','g','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','0','1','2','3','4','5','6','7','8','9'};                 //随机产生4位数字的验证码。        for (int i=0;i<4;i++)        {            //得到随机产生的验证码数字。           // String strRand=String.valueOf(random.nextInt(62));            String strRand = ch[random.nextInt(62)]+"" ;            //产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。            red=random.nextInt(256);            green=random.nextInt(256);            blue=random.nextInt(256);                        //用随机产生的颜色将验证码绘制到图像中。            g.setColor(new Color(red,green,blue));            g.drawString(strRand,15*i+8,20);                        //将产生的四个随机数组合在一起。            captcha.append(strRand);        }        //将四位数字的验证码保存到Session中。        HttpSession session=req.getSession();        //标准答案        session.setAttribute("CAPTCHA",captcha.toString());       // System.out.println(captcha.toString());                //禁止图像缓存。        resp.setHeader("Pragma","no-cache");        resp.setHeader("Cache-Control","no-cache");        resp.setDateHeader("Expires", 0);                                     resp.setContentType("image/jpeg");                //将图像输出到Servlet输出流中。        ServletOutputStream sos=resp.getOutputStream();        ImageIO.write(buffImg, "jpeg",sos);        sos.close();}}