简单验证码生成Java版

Z时代
2024-01-10
分类：IT

验证码大家都知道，它的作用也不用我多说了吧。如果不太清楚请参见百度百科中的解释，一般验证码的生成就是随机产生字符（数字、字母或者汉字等），然后将这些生成的字符绘制成一张图片，再在图片上加上一些干扰元素，如各种线条之类的。好了废话不多说一起往下看：

简单的登录页面（代码并不完整，只有验证码部分）


<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
 <head> 
 <title>验证码</title> 
 <script type="text/javascript"> 
<span style="white-space:pre" data-filtered="filtered"></span><span style="white-space:pre"> </span> //刷新验证码的js函数 
<span style="white-space:pre"> </span>function changeCode() { 
<span style="white-space:pre">  </span>var imgNode = document.getElementById("vimg");     
<span style="white-space:pre">  </span>//重新加载验证码，达到刷新的目的 
<span style="white-space:pre">  </span>imgNode.src = "servlet/AuthImageServlet?t=" + Math.random(); // 防止浏览器缓存的问题  
<span style="white-space:pre"> </span>}  
 </script> 
 </head> 
 <body> 
 <form action="checkServlet" method="post"> 
  <label>输入验证码</label><br/> 
  <input type="text" name="randomCode"/><img id="vimg" title="点击更换" onclick="changeCode();" src="servlet/AuthImageServlet"><br/> 
  <input type="submit" value="submit"> 
 </form> 
 </body> 
</html>

通过session.getAttribute("rand")，获得生成的验证码，然后跟用户输入的进行比较，再根据比较结果做相应的处理。

通过servlet生成验证码：


package com.util.servlet; 
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; 
import javax.servlet.http.HttpSession; 
public class AuthImageServlet extends HttpServlet { 
 private static final String CONTENT_TYPE = "text/html; charset=gb2312";  
 //设置字母的大小,大小  
 private Font mFont = new Font("Times New Roman", Font.PLAIN, 17);  
 public void init() throws ServletException  
 {  
  super.init();  
 }  
 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 service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException  
 {  
  response.setHeader("Pragma","No-cache");  
  response.setHeader("Cache-Control","no-cache");  
  response.setDateHeader("Expires", 0);  
  //表明生成的响应是图片  
  response.setContentType("image/jpeg");  
  int width=100, height=18;  
  BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);  
  Graphics g = image.getGraphics();  
  Random random = new Random();  
  g.setColor(getRandColor(200,250));  
  g.fillRect(1, 1, width-1, height-1);  
  g.setColor(new Color(102,102,102));  
  g.drawRect(0, 0, width-1, height-1);  
  g.setFont(mFont);  
  g.setColor(getRandColor(160,200));  
  //画随机线  
  for (int i=0;i<155;i++)  
  {  
   int x = random.nextInt(width - 1);  
   int y = random.nextInt(height - 1);  
   int xl = random.nextInt(6) + 1;  
   int yl = random.nextInt(12) + 1;  
   g.drawLine(x,y,x + xl,y + yl);  
  }  
  //从另一方向画随机线  
  for (int i = 0;i < 70;i++)  
  {  
   int x = random.nextInt(width - 1);  
   int y = random.nextInt(height - 1);  
   int xl = random.nextInt(12) + 1;  
   int yl = random.nextInt(6) + 1;  
   g.drawLine(x,y,x - xl,y - yl);  
  }  
  //生成随机数,并将随机数字转换为字母  
  String sRand="";  
  for (int i=0;i<6;i++)  
  {  
   int itmp = random.nextInt(26) + 65;  
   char ctmp = (char)itmp;  
   sRand += String.valueOf(ctmp);  
   g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));  
   g.drawString(String.valueOf(ctmp),15*i+10,16);  
  }  
  HttpSession session = request.getSession(true);  
  session.setAttribute("rand",sRand);  
  g.dispose();  
  ImageIO.write(image, "JPEG", response.getOutputStream());  
 }  
}

web.xml中的servlet配置信息：


<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="2.5" 
 xmlns="http://java.sun.com/xml/ns/javaee" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> 
 <servlet> 
 <servlet-name>AuthImageServlet</servlet-name> 
 <servlet-class>com.util.servlet.AuthImageServlet</servlet-class> 
 </servlet> 
 <servlet-mapping> 
 <servlet-name>AuthImageServlet</servlet-name> 
 <url-pattern>/servlet/AuthImageServlet</url-pattern> 
 </servlet-mapping> 
 <welcome-file-list> 
 <welcome-file>index.jsp</welcome-file> 
 </welcome-file-list> 
</web-app>