JSP实现验证码

最新推荐文章于 2020-06-04 15:28:22 发布

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最新推荐文章于 2020-06-04 15:28:22 发布

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本文深入解析了验证码的实现过程，包括JSP页面和Java类Servlet两部分。详细讲解了如何生成随机验证码，如何将其显示在登录页面上，并通过session进行验证。

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验证码的实现分为JSP页面和Java类Servlet两部分：

JSP页面：

<!DOCTYPE html>

<html>

<head>

<title>loginForm.html</title>

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

<meta http-equiv="description" content="this is my page">

<meta http-equiv="content-type" content="text/html; charset=UTF-8">

</head>

<body>

<h3>带有验证码的登陆页面</h3>

<form method="post" action="login.yan" >

用户名：<input type="text" name="usreName" size="10"><br><br/>

密   码：<input type="password" name="password" size="10"><br><br>

验证码：<input type="text" name="userNum" size="4"><img src="loginForm"/><br/><br/>

<input type="submit" value="提交">

</form>

</body>

</html>

Java类：

package com.csdn.session;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

public class loginForm extends HttpServlet {

private static final long serialVersionUID = 1L;

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doPost(request, response);

}

private static int WIDTH = 80;

private static int HEIGHT = 20;

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("image/jpeg");

ServletOutputStream out=response.getOutputStream();

//PrintWriter out = response.getWriter();

response.setHeader("Pragma", "no-cache");

response.setHeader("Cache-Controll", "no-cache");

response.setIntHeader("Expires",0);

//背景

BufferedImage bi = new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB);

Graphics g = bi.getGraphics();

drawBackground(g);

//随机产生验证码

char[] rands=generateCheckCode();

//System.out.println(fun(rands));

HttpSession session=request.getSession();

session.setAttribute("num",fun(rands)+"");//验证码==12-9=3；写入sesion对象

drawRands(g,rands);

ByteArrayOutputStream bos=new ByteArrayOutputStream();

ImageIO.write(bi, "JPEG", bos);

byte[] buf=bos.toByteArray();//将bi对象里面内容转化成字符

out.write(buf);

response.setContentLength(buf.length);

out.flush();

out.close();

}

private int fun(char[] rands){

int num1=Integer.parseInt(rands[0]+"")*10+Integer.parseInt(rands[1]+"");

int num2=Integer.parseInt(rands[2]+"");

int num=0;

if(rands[2]=='+'){

num=num1+num2;

}else{

num=num1-num2;

}

return num;

}

private void drawRands(Graphics g, char[] rands) {

g.setColor(Color.black);

g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));

g.drawString(" "+rands[0],1,20);

g.drawString(" "+rands[1],14,17);

g.drawString(" "+rands[3],30,16);

g.drawString(" "+rands[2],42,18);

g.drawString(" "+rands[4],56,16);

}

private char[] generateCheckCode() {

String chars="0123456789";

String char1="+-";

char[] rands=new char[5];

rands[0]=chars.charAt((int) (Math.random()*2)+1);

rands[1]=chars.charAt((int) (Math.random()*10));

rands[2]=chars.charAt((int) (Math.random()*9)+1);

rands[3]=char1.charAt((int) (Math.random()*2));

rands[4]='=';

return rands;

}

private void drawBackground(Graphics g) {

g.setColor(new Color(0XDCDCDC));

g.fillRect(0,0,WIDTH,HEIGHT);

for(int i=0;i<20;i++){

int x=(int) (Math.random()*WIDTH);

int y=(int) (Math.random()*HEIGHT);

int red=(int) (Math.random()*255);

int greed=(int) (Math.random()*255);

int blue=(int) (Math.random()*255);

g.setColor(new Color(red,greed,blue));

g.drawOval(x, y, 1, 0);

}

}

}

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