(servelet)验证码

验证码的作用

• 为了防止机器人的破坏操作，可以使用验证码技术来防止恶意的发送数据。
• 验证码本质上是一张动态产生的图片。
• 图片的内容会随着程序的运行而随机产生。

验证码的绘制

• 验证码图片的生成需要使用java提供的与绘图有关的一系列API。
• 想要绘图，需要画板，画笔，颜料，背景色，字体等多种类对象配合完成。

验证码图片的绘制步骤

• 1、创建一个内存画板对象
• 2、获取画笔
• 3、为画笔指定颜色
• 4、为画板设置背景色
• 5、绘制一个随机的字符串
• 6、修改画笔颜色
• 7、绘制多条干扰线
• 8、压缩图片并输出到客户端

package com.verificationCode.servelet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.OutputStream;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 ValidateCode extends HttpServlet {    private static final long serialVersionUID = 1L;    public ValidateCode() {        super();    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doPost(request, response);    }    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //0、创建空白图片        BufferedImage image = new BufferedImage(100, 30, BufferedImage.TYPE_INT_RGB);        //1、获取图片画笔        Graphics g = image.getGraphics();        Random r = new Random();        //2、设置画笔颜色        g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));        //3、绘制矩形的背景        g.fillRect(0, 0, 100, 30);        //4、调用自定义的方法，获取长度为5的字母数字组合的字符串        String number = getNumber(5);        HttpSession session = request.getSession();        session.setAttribute("code", number);        g.setColor(new Color(0, 0, 0));        g.setFont(new Font(null, Font.BOLD, 24));        //5、设置颜色字体后，绘制字符串        g.drawString(number, 5, 25);        //6、绘制8条干扰线        for(int i = 0;i<8;i++){            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255), r.nextInt(255)));            g.drawLine(r.nextInt(100), r.nextInt(30), r.nextInt(100), r.nextInt(30));        }        response.setContentType("image/jpeg");        OutputStream ops = response.getOutputStream();        ImageIO.write(image, "jpeg", ops);        ops.close();    }    private String getNumber(int size){        String str = "ASDFGHJLPOIUYTREWQZXCVBNM";        String number = "";        Random r = new Random();        for(int i = 0 ; i<size;i++){            number += str.charAt(r.nextInt(str.length()));        }        return number;    }}

验证码的验证流程

• 请求带有验证码的页面时：
  
  • 通过img标签的src属性获取验证码图片
  • 服务器端生成随机字符串，并绘制
  • 服务器端将生成的随机字符串绑定到session中
• 提交表单及填写的验证码内容时：
  
  • 处理程序将session中绑定的正确的验证码字符串取出来
  • 获取表单提交时填写的验证码内容
  • 比较两者，根据结果做出判断

package com.verificationCode.servelet;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;import javax.servlet.http.HttpSession;public class ActionServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    public ActionServlet() {        super();    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doPost(request, response);    }    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        request.setCharacterEncoding("UTF-8");        response.setContentType("text/html;charset=UTF-8");        PrintWriter out = response.getWriter();        String uri = request.getRequestURI();        String action = uri.substring(uri.lastIndexOf("/")+1, uri.lastIndexOf("."));        //判断动作是否为登录        if(action.equals("login")){            String name = request.getParameter("uname");            String pwd = request.getParameter("pwd");            String number = request.getParameter("vcode");            HttpSession session = request.getSession();            String code = session.getAttribute("code").toString();            if(number.equals(code)&&name.equals("111")&&pwd.equals("111")){                //编程式--设定session超时时间为10秒                //session.setMaxInactiveInterval(10);                session.setAttribute("uname", name);                //重定向到首页                //response.sendRedirect("index.jsp");                response.sendRedirect(response.encodeRedirectUrl("index.jsp"));            } else{                //登录失败                request.setAttribute("msg", "用户名或密码错误");                request.getRequestDispatcher("login.jsp").forward(request, response);            }        }else if(action.equals("logout")){            HttpSession session = request.getSession();            //session失效            session.invalidate();            response.sendRedirect("login.jsp");        }        out.close();    }}

login.jsp代码

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><script type="text/javascript"></script><style type="text/css">    .s1 {        cursor: pointer;    }</style></head><body>    <form action="" method="post">        姓名：<input type="text" /><br>         密码：<input type="password" /><br>        验证码：<input type="text" />         <img src="code" onclick="this.src='code?'+Math.random()" class="s1" title="点击更换"><br>        <input type="submit" value="提交" />    </form></body></html>

web.xml代码

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">  <display-name>verificationCode</display-name>  <servlet>    <servlet-name>ValidateCode</servlet-name>    <servlet-class>com.verificationCode.servelet.ValidateCode</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>ValidateCode</servlet-name>    <url-pattern>/code</url-pattern>  </servlet-mapping>  <servlet>    <servlet-name>ActionServlet</servlet-name>    <servlet-class>com.verificationCode.servelet.ActionServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>ActionServlet</servlet-name>    <url-pattern>*.do</url-pattern>  </servlet-mapping></web-app>