验证码实现（随机背景色及字体颜色，带扰乱线条）

此实现工分三个文件，即：CreatImage.java 生成图像流的类，提供用于生成图片流的方法；images.jsp 图片包装，用于将图片加入到response输出流中；login.jsp 调用前面的jsp，显示验证码。


下面是源代码：


 1 package com;
2
3 import java.awt.Color;
4 import java.awt.Font;
5 import java.awt.Graphics;
6 import java.awt.Image;
7 import java.awt.image.BufferedImage;
8 import java.util.Random;
9
10 import javax.servlet.http.HttpServletRequest;
11 import javax.servlet.http.HttpServletResponse;
12 import javax.servlet.http.HttpSession;
13
14 public class CreatImage{
15
16     private static final long serialVersionUID = 1L;
17     Image image = null;
18     HttpServletRequest request = null;
19     HttpServletResponse response = null;
20
21     public CreatImage(HttpServletRequest request, HttpServletResponse response){
22         this.request = request;
23         this.response = response;
24     }
25
26     public Color getRandColor(int fc,int bc){//给定范围获得随机颜色
27         Random random = new Random();
28         if(fc>255) fc=255;
29         if(bc>255) bc=255;
30         int r=fc+random.nextInt(bc-fc);
31         int g=fc+random.nextInt(bc-fc);
32         int b=fc+random.nextInt(bc-fc);
33         return new Color(r,g,b);
34     }
35
36     public BufferedImage creatImage(){
37          int width=100, height=26;
38          //生成随机类
39          Random random = new Random();
40          BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
41          //获取图形上下文
42          Graphics g = image.getGraphics();
43          // 设定背景色
44          g.setColor(getRandColor(200,250));
45          g.fillRect(0, 0, width, height);
46          //设定字体
47          g.setFont(new Font(“Times New Roman”,Font.PLAIN,22));
48
49          //画边框
50          //g.setColor(getRandColor(200,250));
51          //g.drawRect(0,0,width,height);
52
53          // 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
54          g.setColor(getRandColor(160,200));
55          for (int i=0;i<155;i++){
56            int x = random.nextInt(width);
57            int y = random.nextInt(height);
58            int xl = random.nextInt(12);
59            int yl = random.nextInt(12);
60            g.drawLine(x,y,x+xl,y+yl);
61          }
62          // 取随机产生的认证码(4位数字)
63          //String rand = request.getParameter(“rand”);
64          //rand = rand.substring(0,rand.indexOf(“.”));
65          String str1=randomStr(4);// 得到随机字符
66          HttpSession session = request.getSession();
67          session.setAttribute(“validatenumber”,str1);
68          //System.out.println(str1);
69          for (int i=0;i<4;i++){
70              String rand=str1.substring(i,i+1);
71              // 将认证码显示到图象中
72              g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
73              //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
74              g.drawString(rand,20*i+12,20);
75          }
76          // 图象生效
77          g.dispose();
78          return image;
79     }
80
81   // 得到随机字符
82   public  String randomStr(int n) {
83       String str1 = “ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890″;
84       String str2 = “”;
85       int len = str1.length() – 1;
86       double r;
87       for (int i = 0; i < n; i++) {
88           r = (Math.random()) * len;
89           str2 = str2 + str1.charAt((int) r);
90       }
91       return str2;
92   }
93 }
 


 1 <%@ page language=”java” contentType=”image/jpeg ; charset=UTF-8″
2     pageEncoding=”UTF-8″ import=”java.awt.*,java.awt.image.*,javax.imageio.*,java.io.*”%>
3 <%@ page import =”com.CreatImage”%>
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11 <%
12     response.setHeader(“Pragma”,”No-cache”);
13     response.setHeader(“Cache-Control”,”no-cache”);
14     response.setDateHeader(“Expires”, 0);
15
16     CreatImage c = new CreatImage(request,response);
17     BufferedImage  image = c.creatImage();
18     OutputStream b = response.getOutputStream();
19 %>
20 <%
21     ImageIO.write(image, “JPEG”, response.getOutputStream());
22     //必须添加以下两行否则tomcat下jsp出现getOutputStream() has already been called for this response 异常
23     out.clear();
24     out = pageContext.pushBody();
25 %>
26
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注意   contentType=”image/jpeg ; charset=UTF-8″
1 <%@ page language=”java” contentType=”text/html; charset=UTF-8″
2     pageEncoding=”UTF-8″%>
3 <%
4     String path = request.getContextPath();
5 %>
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用户名：
密  码：
验证码：		/images.jsp”/>

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