(servelet)验证码

柔光的暖阳◎ 2021-10-06 13:14 229阅读 0赞

#### **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>