javaWeb中的验证码

　　在做网站中，经常用到验证码验证什么的。如登陆验证...随着技术的升级，验证码技术也升级了。验证码的出现时为了防止‘暴力破解’账号。下面我就讲我最近所学的一个普通写验证码的代码整理如下:

　　第一步:servlet中的代码

package com.zuxia.servlet;

import java.awt.BasicStroke;  
import java.awt.Color;  
import java.awt.Font;  
import java.awt.Graphics;  
import java.awt.Graphics2D;  
import java.awt.GraphicsEnvironment;  
import java.awt.geom.AffineTransform;  
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 DrawImageCode extends HttpServlet {  
  
    private Color getRandColor(int s, int e) {  
        Random random = new Random();  
        if (s > 255)  
            s = 255;  
        if (e > 255)  
            e = 255;  
        int r = random.nextInt(e - s) + s; // 随机生成RGB中的R值  
        int g = random.nextInt(e - s) + s; // 随机生成RGB中的G值  
        int b = random.nextInt(e - s) + s; // 随机生成RGB中的B值  
        return new Color(r, g, b);  
    }  
  
  
    public void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
  
        this.doPost(request, response);  
    }  
  
    public void doPost(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
  
        response.setHeader("Pragma", "No-cache");  
        response.setHeader("Cache-Control", "No-cache");  
        response.setDateHeader("Expires", 0);  
        //指定生成的响应图片  
        response.setContentType("image/jpeg");  
        int width = 150;                            //指定生成验证码图片的宽度  
        int heigh = 60;                         //指定生成验证码图片的高度  
            //获得图像数据缓冲对象  
        BufferedImage bi = new BufferedImage(width,heigh,BufferedImage.TYPE_INT_RGB);  
            //获得图形上下文的抽象基类  
        Graphics g = bi.getGraphics();  
        Random r = new Random();  
        Font f = new Font("黑体",Font.PLAIN,60);  //定义字体样式  
        g.setColor(getRandColor(200, 250));     //设置背景颜色  
        g.fillRect(0, 0, width, heigh);         //绘制背景  
        g.setFont(f);                           //设置字体  
        g.setColor(getRandColor(180, 200));     //设置前景颜色  
          
          
        Graphics2D g2d = (Graphics2D) g;  
        //画一条折线       
        //BasicStroke bs=new BasicStroke(5f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //创建一个供画笔选择线条粗细的对象  
        //g2d.setStroke(bs);              //改变线条的粗细  
        g2d.setColor(Color.DARK_GRAY);      //设置当前颜色为预定义颜色中的深灰色  
        int[] xPoints=new int[8];  
        int[] yPoints=new int[8];  
        for(int j=0;j<8;j++){  
            xPoints[j]=r.nextInt(width - 1);  
            yPoints[j]=r.nextInt(heigh - 1);  
        }  
        g2d.drawPolyline(xPoints, yPoints,8);  
          
        String sRand = "";  
        String ctmp = "";  
        int itmp = 0;  
        for (int i = 0; i < 6; i++) {  
            switch (r.nextInt(2)) {  
            case 1:  
                itmp = r.nextInt(26) + 65; // 生成A~Z的字母  
                ctmp = String.valueOf((char) itmp);  
                break;  
            default:  
                itmp = r.nextInt(10) + 48; // 生成0~9的数字  
                ctmp = String.valueOf((char) itmp);  
                break;  
            }  
            sRand += ctmp;  
            //设置每个字符的随机颜色  
            Color color = new Color(20 + r.nextInt(210), 20 + r.nextInt(210), 20 + r.nextInt(210));  
            g2d.setColor(color);  
            //设置每个字符的随机字体  
            g2d.setFont(this.getRandomFont());  
            //设置每个字符的随机旋转  
            AffineTransform at = new AffineTransform();  
            int number = r.nextInt(3)-1;  
            double role = number*r.nextDouble()*(Math.PI/4);  
            at.setToRotation(role,25*i+5,55-r.nextInt(20)); //role:旋转角度,后面两个参数是设置围绕坐标点旋转  
            g2d.setTransform(at);  
              
            g2d.drawString(ctmp, 25*i+5,55-r.nextInt(20));  
        }  
           HttpSession session = request.getSession(true);  
           session.setMaxInactiveInterval(5*60);//设置session对象5分钟失效  
           session.setAttribute("code", sRand.toString());  
  
           g2d.dispose();  
  
            System.out.println(sRand);  
            ImageIO.write(bi, "JPEG", response.getOutputStream());  
              
              
    }  
      
     
     public static Font getRandomFont() {    
            //String[] fonts = {"Georgia", "Verdana", "Arial", "Tahoma", "Time News Roman", "Courier New", "Arial Black", "Quantzite"};    
            String[] fonts = {"a_TrianglerCmUp","Astarisborn","WishfulWaves"};  
            Random r = new  Random();  
           int fontIndex = r.nextInt(fonts.length);  
            return new Font(fonts[fontIndex],  r.nextInt(3),50-r.nextInt(20));    
        }  
}  

　　　　第二步：jsp页面引用这servlet，用以显示效果

<html>
<head>
<tiltle>我是验证码页面哦</title>

</head>

<body>
     <div><img src="DrawImageCode " alt="验证码"/></div>
</body>
</html>

　　提示：DrawImageCode是已建好的servlet的路径名哦......