bbs小项目整理（四）（验证码制作）

1.首先完成我么验证码的绘制，这里采用的是通过servlet的方式来绘制出我们的验证码图片的，代码如下：
　在com.congbbs.servlet包下建立验证码的绘制servlet

package com.congbbs.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
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;

public class DrawImage extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
    public static final int WIDTH = 120;//定义图片的宽和高
    public static final int HEIGHT= 30;
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        // 1.在内存中创建一张图片
        BufferedImage bi = new BufferedImage(WIDTH, HEIGHT,
                BufferedImage.TYPE_INT_RGB);
        // 2.得到图片
        Graphics g = bi.getGraphics();
        // 3.设置图片的背景颜色
        setBackGround(g);
        // 4.设置图片的边框
        setBorder(g);
        // 5.在图片上话干扰线
        drawRandomLine(g);
        String random = drawRandomNum((Graphics2D) g);//生成验证码图片
        // 7.将随机数存在session中
        request.getSession().setAttribute("chenkcode", random);
        // 8.设置响应头通知浏览器以图片的形式打开
        response.setContentType("image.jpeg");
        // 9.设置相应头通知浏览器不要缓存
        response.setDateHeader("expries", -1);
        response.setHeader("Cache-Control", "nc-cache");
        response.setHeader("Pragma", "no-Cache");
        // 10.将图片写给浏览器
        ImageIO.write(bi, "jpg", response.getOutputStream());
    }
    
    // 设置图片的背景颜色
        public void setBackGround(Graphics g) {
            g.setColor(Color.WHITE);
            g.fillRect(0, 0, WIDTH, HEIGHT);
        }

        // 设置图片的边框

        public void setBorder(Graphics g) {
            g.setColor(Color.BLUE);
            g.drawRect(1, 1, WIDTH - 2, HEIGHT - 2);
        }

        // 在图片上画随机线条

        private void drawRandomLine(Graphics g) {
            g.setColor(Color.GREEN);

            for (int i = 0; i < 5; i++) {
                int x1 = new Random().nextInt(WIDTH);
                int y1 = new Random().nextInt(HEIGHT);
                int x2 = new Random().nextInt(WIDTH);
                int y2 = new Random().nextInt(HEIGHT);
                g.drawLine(x1, y1, x2, y2);
            }
        }

        // 获得随机的字符
        private String drawRandomNum(Graphics2D g) {
            // 设置颜色
            g.setColor(Color.RED);
            // 设置字体
            g.setFont(new Font("宋体", Font.BOLD, 20));
            // 数字和字母组合
            String baseNumLetter = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
            //返回随机绘制的数字和字母
            return createRandomChar(g, baseNumLetter);

        }

        private String createRandomChar(Graphics2D g, String baseChar) {
            StringBuffer sb = new StringBuffer();
            int x = 5;
            String ch = "";
            // 控制数字
            for (int i = 0; i < 4; i++) {
                int degree = new Random().nextInt() % 30;
                ch = baseChar.charAt(new Random().nextInt(baseChar.length())) + "";
                sb.append(ch);
                // 正向角度
                g.rotate(degree * Math.PI / 180, x, 20);
                g.drawString(ch, x, 20);
                // 反向角度
                g.rotate(-degree * Math.PI / 180, x, 20);
                x += 30;
            }
            return sb.toString();
        }
}

 2 最后在我们的登录界面添加一段javascript代码就能变换验证码了

<script type="text/javascript">
    function changImg(){
        document.getElementById("validateCodeImg").src="${pageContext.request.contextPath}/DrawImage?"+Math.random();
    }
</script>

3 登录界面的表现工作基本完成了，主要是一个简单的验证码绘制。