产生彩色验证码_(javabean实现)

答案：文件名：Image.java
==================================================================
/*
 * Created on 2004-8-4
 *
 * To change the template for this generated file go to
 * Window>Preferences>Java>Code Generation>Code and Comments
 */
package myclass.test;

import java.awt.*;
import java.awt.image.*;
import java.util.*;

/**
 * @author 
 *
 * To change the template for this generated type comment go to
 * Window>Preferences>Java>Code Generation>Code and Comments
 */
public class Image {
  
  public String sRand="";
 
  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);
   }
  public BufferedImage creatImage(){

 // 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 rand = request.getParameter("rand");
    //rand = rand.substring(0,rand.indexOf("."));
    
    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);
    }
    // 图象生效
    g.dispose();
    return image;
  }
}
======================================================================
image.jsp(对bean的引用)

<%@ page contentType="image/jpeg" import="javax.imageio.*" %>
<jsp:useBean id="image" scope="session" class="myclass.test.Image"/>

<%
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

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

// 输出图象到页面
ImageIO.write(image.creatImage(), "JPEG", response.getOutputStream());


%> 

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