servlet输出随机图片(验证码)

package com.baidu.web.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;


//输出一张随机图片
public class ResponseDemo extends HttpServlet {
    
    public static final int WIDTH = 120;
    public static final int HEIGHT = 25;
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        //BufferedImage image = new BufferedImage(width, height, imageType)
        
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        
        Graphics graphics = image.getGraphics();
        
        //1.设置背景色
        setBackGround(graphics);
        
        //2.设置边框
        setBorder(graphics);
        
        //3.画干扰线
        drawRandomLine(graphics);
        
        //4.写随机数
        Graphics2D graphics2d = (Graphics2D) graphics;
        drawRandomNum(graphics2d);
        
        //5.图形写给浏览器
        drawToBrower(graphics ,response,image);
        
        //控制浏览器不要缓存
        response.setDateHeader("expries", -1);
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Prama", "no-cache");
        ImageIO.write(image, "jpg", response.getOutputStream());
    }

    private void drawRandomNum(Graphics2D graphics) {
        graphics.setColor(Color.RED);
        graphics.setFont(new Font("宋体" , Font.BOLD , 20));
        
        //汉字区间 [u4e00 u9fa5]
        //常用的汉字
        String baseString = "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";
        
        int x = 5;
        for(int i = 0;i < 4; i++){
            
            int degree = new Random().nextInt()%30;
            
            String ch = baseString.charAt(new Random().nextInt(baseString.length())) + "";
            
            graphics.rotate(degree*Math.PI/180 , x , 20);//设置旋转角度
            
            graphics.drawString(ch, x , 20);
            
            graphics.rotate(-degree*Math.PI/180, x ,20);
            
            x += 30;
            
            
        }
    }

    private void drawToBrower(Graphics graphics, HttpServletResponse response,
            BufferedImage image) {
        
        response.setContentType("image/jpeg");
        try {
            ImageIO.write(image, "jpg", response.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void drawRandomLine(Graphics graphics) {
        graphics.setColor(Color.GREEN);
        
        for(int i = 0;i < 5 ;i++){
            int xStartPoint = new Random().nextInt(WIDTH);
            int yStartPoint = new Random().nextInt(HEIGHT);
            
            int xEndPoint = new Random().nextInt(WIDTH);
            int yEndPoint = new Random().nextInt(HEIGHT);
            
            graphics.drawLine(xStartPoint, yStartPoint, xEndPoint, yEndPoint);
        }
    }


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


    private void setBackGround(Graphics graphics) {
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, WIDTH, HEIGHT);
    }


    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        
        
    }
}

html

<!DOCTYPE html>
<html>
  <head>
    <title>register.html</title>
    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    
    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
    
    <script type="text/javascript">
        function changeImage(img){
            //alert("haha");
            img.src = img.src + "?" + new Date().getTime();
        }
    </script>

  </head>
  
  <body>
    <form action="">
        用户名：<input type="text" name="username"><br/>
         密码: <input type="password" name="password"><br/>
         认证码:<input type="text" name="checkcode"><img src="/TestJsp/servlet/ResponseDemo" onclick="changeImage(this)">
        <input type="submit" value="注册">
    </form>
  </body>
</html>

参考资料

http://blog.csdn.net/lanshengsheng2012/article/details/8970090