java web验证码实现代码分享

java web验证码实现代码分享

验证码的作用：通常的登录或者注册系统时，都会要求用户输入验证码，以此区别用户行为和计算机程序行为，目的是有人防止恶意注册、暴力破解密码等。

实现验证码的思路：用 server 实现随机生成数字和字母组成图片的功能，用 jsp 页面实现显示验证码和用户输入验证码的功能，再用 server 类分别获取图片和用户输入的数据，判断两个数据是否一致。 

代码实现

1.编写数字、英文随机生成的 server 类，源码：

package com;

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 java.io.PrintWriter;

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 logcheck extends HttpServlet {

public logcheck() {

super();

}

public void destroy() {

super.destroy();

}

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doPost(request, response);

}

/*实现的核心代码*/

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("image/jpeg");

HttpSession session=request.getSession();

int width=60;

int height=20;

//设置浏览器不要缓存此图片

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

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

response.setDateHeader("Expires", 0);

//创建内存图像并获得图形上下文

BufferedImage image=new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);

Graphics g=image.getGraphics();

/*

* 产生随机验证码

* 定义验证码的字符表

*/

String chars="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

char[] rands=new char[4];

for(int i=0;i<4;i++){

int rand=(int) (Math.random() *36);

rands[i]=chars.charAt(rand);

}

/*

* 产生图像

* 画背景

*/

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

g.fillRect(0, 0, width, height);

/*

* 随机产生120个干扰点

*/

for(int i=0;i<120;i++){

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

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

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

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

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

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

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

}

g.setColor(Color.BLACK);

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

//在不同高度输出验证码的不同字符

g.drawString(""+rands[0], 1, 17);

g.drawString(""+rands[1], 16, 15);

g.drawString(""+rands[2], 31, 18);

g.drawString(""+rands[3], 46, 16);

g.dispose();

//将图像传到客户端

ServletOutputStream sos=response.getOutputStream();

ByteArrayOutputStream baos=new ByteArrayOutputStream();

ImageIO.write(image, "JPEG", baos);

byte[] buffer=baos.toByteArray();

response.setContentLength(buffer.length);

sos.write(buffer);

baos.close();

sos.close();

session.setAttribute("checkcode", new String(rands));

}

public void init() throws ServletException {

// Put your code here

}

}

2.用于显示验证码的页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

&nbsp&nbsp&nbsp&nbsp&nbsp

3.用于检验输入的验证码是否正确：

package com;

import java.io.IOException;

import java.io.PrintWriter;

import javax.jms.Session;

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 yanzheng extends HttpServlet {

public yanzheng() {

super();

}

public void destroy() {

super.destroy();

}

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doPost(request, response);

}

/*核心代码*/

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

String info=null;

/*获取输入的值*/

String value1=request.getParameter("name");

/*获取图片的值*/

HttpSession session=request.getSessiohttp://n();

String value2=(String)session.getAttribute("checkcode");

/*对比两个值（字母不区分大小写）*/

if(value2.equalsIgnoreCase(value1)){

info="验证码输入正确";

}else{

info="验证码输入错误";brmMgYjg

}

System.out.println(info);

request.setAttribute("info", info);

request.getRequestDispatcher("/login.jsp").forward(request, response);

}

public void init() throws ServletException {

// Put your code here

}

}

4.显示输入结构界面（输入验证码是否正确）：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

<%=request.getAttribute("info") %>

5.项目结构、效果截图：

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