servlet：

package com.servlet.image;  
 
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.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
 
public class ServletImage extends HttpServlet {  
 
    public void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
 
        response.setContentType("image/jpeg");  
          
        //设置页面缓存  
        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 = 60, height = 20;  
        BufferedImage image = new BufferedImage(width, height,  
                BufferedImage.TYPE_INT_RGB);  
          
        //获取图形上下文  
        Graphics g = image.getGraphics();  
          
        //生成随机类  
        Random random = new Random();  
          
        //设定背景色  
        g.setColor(getRandColor(200, 250));  
        g.fillRect(0, 0, width, height);  
          
        //设定字体  
        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));  
          
        //画边框  
        g.setColor(new Color(10+random.nextInt(211),10+random.nextInt(211),  
                10+random.nextInt(211)));  
        g.drawRect(0, 0, width-1, height-1);  
          
        //随机产生155条干扰线，使图像中的认证码不易被其他程序探测到  
        g.setColor(getRandColor(160, 200));  
        for(int i=0; i<155; i++) {  
            int x = random.nextInt(width);  
            int y = random.nextInt(height);  
            int x1 = random.nextInt(12);  
            int y1 = random.nextInt(12);  
            g.drawLine(x, y, x+x1, y+y1);  
        }  
          
        //取随机产生的认证码（4位数字)  
        String sRand = "";  
        for(int i=0; i<4; i++) {  
            String rand = String.valueOf(random.nextInt(10));  
            sRand += rand;  
              
            //将认证码显示到图象中  
            g.setColor(new Color(20+random.nextInt(110),   
                    20+random.nextInt(110), 20+random.nextInt(110)));  
            g.drawString(rand, 13*i+6, 16);  
              
        }  
          
        request.getSession().setAttribute("rand", sRand);  
          
        //图象生效  
        g.dispose();  
          
        //输出图象到页面  
        ImageIO.write(image,"JPEG",response.getOutputStream());  
          
    }  
      
    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);  
    }  
 
    public void doPost(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
        doGet(request, response);  
    }  
 
} 
下期预告：你能用多少种方法实现HelloWorld,O(∩_∩)O~

这个我以前也实现过了

你太无聊了。。。。