实现JAVA验证码（超简单带有源码）-优快云博客

本文链接：https://blog.youkuaiyun.com/kzbpp/article/details/8596194

本文介绍了一个基于Java的验证码生成及验证系统实现。该系统通过HTML和JavaScript生成验证码图片，并使用Servlet进行图片绘制，同时利用Session存储验证码以进行后续验证。

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yanZm.jsp:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"content="text/html; charset=gb2312"/>
<title>验证码</title>
<script type="text/javascript"language="javascript">
functionchangeImg(){
   vara=document.getElementByIdx_x("mySpan");
  a.innerHTML='<img align="middle"src="ImageServlet"/> <a href="#"onclick="changeImg();">看不清</a>';//?????mySpan??λ??
}
</script>
</head>
<%@ page language="java"pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() +"://"
   + request.getServerName() +":" + request.getServerPort()
   + path +"/";
%>

</html>

servlet:ImageServlet.java

package com.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;
importjavax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ImageServlet extends HttpServlet{
private static final long serialVersionUID =1L;
public void doGet(HttpServletRequest request, HttpServletResponseresponse)
   throws ServletException,IOException {
           doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponseresponse)
   throws ServletException,IOException {
intwidth=150;//验证码图片宽度
intheight=60;//验证码图片高度
BufferedImage image=newBufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
Graphicsg=image.getGraphics();
Random random=newRandom();//创建一个随机类
g.setColor(getRandColor(200,250));//背景颜色要偏淡
g.fillRect(0, 0, width,height);//画背景
g.setColor(getRandColor(0,255));//边框颜色
       g.drawRect(0, 0, width-1,height-1);//画边框
g.setColor(getRandColor(160,200));//随机产生5条干扰线，使图象中的认证码不易被其它程序探测到
for(inti=0;i<8;i++){
   intx=random.nextInt(width);
   inty=random.nextInt(height);
   intx1=random.nextInt(width);
   inty1=random.nextInt(height);
   g.drawLine(x, y, x1,y1);
}
g.setColor(getRandColor(160,200));//随机产生100点，使图象中的认证码不易被其它程序探测到
for(inti=0;i<100;i++){
   intx=random.nextInt(width);
   inty=random.nextInt(height);
   g.drawLine(x, y, x,y);
}
       Font font = new Font("Times New Roman",Font.ITALIC,38); //创建字体，字体的大小应该根据图片的高度来定。
       g.setFont(font);//设置字体
       int length = 6; //设置默认生成4个验证码
Strings="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";// 设置备选验证码:包括"a-z"和数字"0-9"
String sRand="";

       // 用随机产生的颜色将验证码绘制到图像中。
       //生成随机颜色(因为是做前景，所以偏深)
       //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.setColor(newColor(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
for(inti=0;i<length;i++){
   String ch=String.valueOf(s.charAt(random.nextInt(s.length())));
  sRand+=ch;
   g.drawString(ch, 22*i+12,(random.nextInt(5)-2)*i+40);
}
//将生成的字符串存储在session中
HttpSessionsession=request.getSession();
session.setAttribute("checkCode",sRand);
g.dispose();//图像生效
//禁止图像缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires",0);
response.setContentType("image/jpeg");
//创建二进制的输出流
ServletOutputStreamsos=response.getOutputStream();
       // 将图像输出到Servlet输出流中。
       ImageIO.write(image, "jpeg", sos);
       sos.flush();
       sos.close();
}

public Color getRandColor(int lower,intupper){
Random random = newRandom();
if(upper>255)
  upper=255;
if(upper<1)
  upper=1;
if(lower<1)
  lower=1;
if(lower>255)
  lower=255;
intr=lower+random.nextInt(upper-lower);
intg=lower+random.nextInt(upper-lower);
intb=lower+random.nextInt(upper-lower);
return newColor(r,g,b);
}
}

resultServlet.java

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

public class resultServlet extends HttpServlet {

public void doGet(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException {

doPost(request, response);
}

public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException {

response.setContentType("text/html;charset=utf-8");
String validateC =(String)request.getSession().getAttribute(
   "checkCode");
String veryCode =request.getParameter("txtyzm");
PrintWriter out =response.getWriter();
if (veryCode == null || "".equals(veryCode)){
out.print("<scriptlanguage='javascript'>");
  out.println("alert('验证码为空')");
  out.print("</script>");
} else {
   if(validateC.equals(veryCode)) {
   out.print("<scriptlanguage='javascript'>");
   out.println("alert('验证码正确')");
   out.print("</script>");
   } else {
   out.print("<scriptlanguage='javascript'>");
   out.println("alert('验证码错误')");
   out.print("</script>");
   }
}
out.flush();
out.close();
}

}

web.xml:

<?xml version="1.0"encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<servlet>
<servlet-name>ImageServlet</servlet-name>
<servlet-class>com.servlet.ImageServlet</servlet-class>
</servlet>

<servlet>
<servlet-name>resultServlet</servlet-name>
<servlet-class>com.servlet.resultServlet</servlet-class>
</servlet>

   <servlet-mapping>
   <servlet-name>ImageServlet</servlet-name>
   <url-pattern>/ImageServlet</url-pattern>
</servlet-mapping>

<servlet-mapping>
   <servlet-name>resultServlet</servlet-name>
   <url-pattern>/resultServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
   <welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>