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开发学院WEB开发Jsp java servlet/jsp随机验证码 阅读

java servlet/jsp随机验证码

 2009-03-26 20:51:20 来源:WEB开发网   
核心提示:package com.banding.web.util;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;

package com.banding.web.util;

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.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class Image extends HttpServlet {
 
 //public static final long serialVersionUID = 1L ;
 
   //PRivate static final String CONTENT_TYPE = "text/html; charset=GBK";

   public Color getRandColor(int fc, int bc) { //给定范围获得随机颜色
     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);
   }

   //Initialize global variables
   public void init() throws ServletException {
   }

   //Process the HTTP Get request
   public void doGet(HttpServletRequest request, HttpServletResponse response) throws
       ServletException, IOException {
     //设置页面不缓存
     response.setHeader("Pragma", "No-cache");
     response.setHeader("Cache-Control", "no-cache");
     response.setDateHeader("Expires", 0);

 // 在内存中创建图象
     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());
 //g.drawRect(0,0,width-1,height-1);

 // 随机产生155条干扰线,使图象中的认证码不易被其它程序探测到
     g.setColor(getRandColor(160, 200));
     for (int i = 0; i < 155; i++) {
       int x = random.nextInt(width);
       int y = random.nextInt(height);
       int xl = random.nextInt(12);
       int yl = random.nextInt(12);
       g.drawLine(x, y, x + xl, y + yl);
     }

 // 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)));
 //调用函数出来的颜色相同,可能是因为种子太接近,所以只能直接生成
       g.drawString(rand, 13 * i + 6, 16);
     }

 // 将认证码存入session
     request.getSession().setAttribute("rand", sRand);

 // 图象生效
     g.dispose();

 // 输出图象到页面
 //ImageIO.write(image, "JPEG", response.getOutputStream());
     JPEGImageEncoder encode = JPEGCodec.createJPEGEncoder(response.
         getOutputStream());
     encode.encode(image);

   }

   //Clean up resources
   public void destroy() {
   }
}

上面的代码可以直接用,在web.xml中配置好以后就可以在浏览器中访问这个servlet,能得到下面的效果验证码的效果图

若要在jsp页面中使用这个验证码 只需用一个 <img src="那个servlet的地址" />

这样就好了

Tags:java servlet jsp

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